Section 2 Applications

**Chapter 5**

**Abstract**

Industry

their characteristics will be given.

**1. Introduction**

**83**

**Keywords:** clays, ceramic, limestone clays, calcium carbonate

Limestone Clays for Ceramic

*Herbet Alves de Oliveira and Cochiran Pereira dos Santos*

Limestone clays are used in the ceramic segment in the manufacture of bricks, ceramic tiles, and in the production of cement, among others. Limestone can be present in soils in pure form or as a contaminant, but always from marine environments. The limestone after burning can present a high loss of mass (35–45%), which can cause serious problems with the sintering of ceramic products such as bricks, tiles. The calcium or magnesium carbonate once dissociated forms calcium oxide (CaO) and releases carbon dioxide (CO2). CaO in contact with water subsequently experiences very high expansions that can cause cracks in the materials. Researchers have studied procedures to inhibit limestone action on clays as well as to set the correct temperature for firing. In this chapter, examples of clays with different percentages of calcium carbonate (CaCO3) that are used in the ceramic segment and

Clays are inorganic, natural, earthy, and fine-grained materials that acquire plasticity when mixed with water [1]. For sedimentologists, a clay is a raw material whose grain size is less than 2 μm. Like clays, in turn, there are rocks made up of clay minerals and may contain other minerals such as quartz, feldspar, mica, calcite, hematite, and organic matter as accessories [2]. A clay, once ground and mixed with water, in addition to presenting excellent workability in the fresh state, after drying, becomes extremely rigid. After burning normally above 800°C, it acquires great resistance [3]. Clays are used worldwide in the ceramic industry, especially in bricks, coatings, and others. However, clays are formed from the weathering of explosion and can be contaminated with several minerals among them or carbonate, which can alter the shape that causes the following burns. Limestone may be present in colloidal form, or coarse particles. However, in all cases it is impossible to separate or calculate this. Some researchers have tried to reduce the size of the variations to improve the chemical changes. According to Barba et al. [4], calcium carbonate and magnesium carbonate are the main constituents of carbonate sedimentary rocks. Anionic carbonate groups are strongly activated units and share oxygen with each other. They are responsible for the properties of these minerals. The most important anhydrous carbonates belong to three isostructural groups: the calcite group, the aragonite group, and the dolomite group. Among these, the minerals most used in the ceramic industry are calcite and dolomite, as they are

### **Chapter 5**

## Limestone Clays for Ceramic Industry

*Herbet Alves de Oliveira and Cochiran Pereira dos Santos*

### **Abstract**

Limestone clays are used in the ceramic segment in the manufacture of bricks, ceramic tiles, and in the production of cement, among others. Limestone can be present in soils in pure form or as a contaminant, but always from marine environments. The limestone after burning can present a high loss of mass (35–45%), which can cause serious problems with the sintering of ceramic products such as bricks, tiles. The calcium or magnesium carbonate once dissociated forms calcium oxide (CaO) and releases carbon dioxide (CO2). CaO in contact with water subsequently experiences very high expansions that can cause cracks in the materials. Researchers have studied procedures to inhibit limestone action on clays as well as to set the correct temperature for firing. In this chapter, examples of clays with different percentages of calcium carbonate (CaCO3) that are used in the ceramic segment and their characteristics will be given.

**Keywords:** clays, ceramic, limestone clays, calcium carbonate

### **1. Introduction**

Clays are inorganic, natural, earthy, and fine-grained materials that acquire plasticity when mixed with water [1]. For sedimentologists, a clay is a raw material whose grain size is less than 2 μm. Like clays, in turn, there are rocks made up of clay minerals and may contain other minerals such as quartz, feldspar, mica, calcite, hematite, and organic matter as accessories [2]. A clay, once ground and mixed with water, in addition to presenting excellent workability in the fresh state, after drying, becomes extremely rigid. After burning normally above 800°C, it acquires great resistance [3]. Clays are used worldwide in the ceramic industry, especially in bricks, coatings, and others. However, clays are formed from the weathering of explosion and can be contaminated with several minerals among them or carbonate, which can alter the shape that causes the following burns. Limestone may be present in colloidal form, or coarse particles. However, in all cases it is impossible to separate or calculate this. Some researchers have tried to reduce the size of the variations to improve the chemical changes. According to Barba et al. [4], calcium carbonate and magnesium carbonate are the main constituents of carbonate sedimentary rocks. Anionic carbonate groups are strongly activated units and share oxygen with each other. They are responsible for the properties of these minerals. The most important anhydrous carbonates belong to three isostructural groups: the calcite group, the aragonite group, and the dolomite group. Among these, the minerals most used in the ceramic industry are calcite and dolomite, as they are

low-cost raw materials, in addition to having favorable physical and chemical properties and available deposits. Second, Padoa [5] adds that when CaCO3 is small, a decomposition can be complete and the calcium oxide reaches later with other mass components forming calcium silicates and silicon aluminates (wollastonite, anortite, gehlenite etc.) during sintering. Barba et al. [4] mentioned that the raw materials of clay when burned at high temperatures produce crystal phases that influence the properties of ceramic products. Calcite exerts a bleaching action on burnt products when added to a formulated mass of clays (in proportions above 5% and less than 30%) and at the same time decreases its expansion by legislation, as it forms crystalline and liquid phases, including cycles temperature and firing adopted. Calcite and dolomite are the most important representatives of carbonates in the ceramic industry. They are used as main components in the manufacture of ceramic tiles with high water absorption. These coatings include "porous coatings" or "tiles." These products are designed or used on walls and are not suitable for application on floors, as they have undesirable technical characteristics, such as mechanical resistance, incompatibility with use. According to Amorós [6], properties of parts of a ceramic product are registered by crystalline phases formed based on calcium and magnesium as ghelenite (SiO2Al2O32CaO) and anortite (2SiO2Al2O3CaO). To achieve these phases, use the dolomite calcium oxide and/or magnesium reaction with a remaining clay structure proven by its thermal decomposition.

The calculation in general can affect the ceramic product in two ways: low percentages (up to 3%) and high temperature (above 1180°C) result in flow agents, that is, materials that contribute to reduce water absorption and increase the resistance of ceramic products. Above 3%, they can act as a foundation at temperatures above 1170°C [7].

In this chapter, we will highlight properties of limestone clays and their application in the ceramic industry.

> for providing significant improvements when incorporated into pure polymeric materials and conventional composites. The clay modification process occurs preferably through the ionic exchange of the exchangeable cations of its crystalline

*Crystalline structure of a montmorillonite. (a) Montmorillonite structure, composed of Si, Al, and O.*

*Kaolinite structure. (a) Si*d*O tetrahedra on the bottom half of the layer and Al*d*O,OH octahedra on the top*

The basic structural unit of the illites is the same as that of the montmorillonites except that in illites, the silicon atoms in the silica layers are partially replaced by aluminum. Therefore, there are free valences in the boundary layers of the structural units, which are neutralized by K cations, arranged between the overlapping units. The structural scheme of the illites is shown in **Figure 3**. The K cation is the one that best adapts to the hexagonal meshes of the oxygen planes of the layers of silica tetrahedron and is not displaced by other cations. The water adsorption and cation exchange capacity is due only to the broken connections at the ends of the layers. The average diameter of the illites varies between 0.1 and 0.3 μm. When the replacement of silicon in the tetrahedron layers by aluminum in the illites is small, the connections between the structural units provided by the K cations may be deficient and will allow water to enter. When this occurs, the properties of the illites

Chlorites are minerals made up of four hydrated aluminum and magnesium

silicate layers, containing Fe (II) and Fe (III) as shown in **Figure 4**.

are close to the properties of montmorillonites [3].

structure.

**Figure 2.**

**Figure 1.**

*half. (b) Dioctahedral structure.*

*Limestone Clays for Ceramic Industry*

*DOI: http://dx.doi.org/10.5772/intechopen.92506*

*(b) Sheets of dioctahedral and trioctahedral silicates.*

**2.3 Illite**

**2.4 Chlorite**

**85**

### **2. Clays**

Clays are hydrated aluminum silicates with crystalline structure arranged in layers, consisting of continuous sheets of SiO4 tetrahedrons, ordered in a hexagonal shape, condensed with octahedral sheets of di and trivalent metal hydroxides, usually below 2 μm. They are materials that in contact with water become plastic, a fundamental characteristic for conformation of ceramic products because it provides mechanical resistance in the pressing, extrusion, or gluing process. Clays are mixtures of various clay minerals such as kaolinite, illite, and montmorillonite, which may or may not contain impurities [3, 8].

### **2.1 Kaolinite**

The kaolinite with structural formula Al2O32SiO22H2O has a dioctahedral structure, which consists of a tetrahedral layer linked by an octahedral layer. Pure kaolinites usually have low plasticity, see **Figure 1**.

### **2.2 Montmorillonite**

Montmorillonites are a set of family of clay minerals, composed of dioctahedral and trioctahedral silicate sheets, see **Figure 2(a)** and **(b)**. The most outstanding feature of these minerals is their ability to absorb water molecules [8, 9]. It has 80% of exchangeable cations in the galleries and 20% on the lateral surfaces. The modification of montmorillonite clays has aroused scientific and technological interest

*Limestone Clays for Ceramic Industry DOI: http://dx.doi.org/10.5772/intechopen.92506*

### **Figure 1.**

low-cost raw materials, in addition to having favorable physical and chemical properties and available deposits. Second, Padoa [5] adds that when CaCO3 is small, a decomposition can be complete and the calcium oxide reaches later with other mass components forming calcium silicates and silicon aluminates (wollastonite, anortite, gehlenite etc.) during sintering. Barba et al. [4] mentioned that the raw materials of clay when burned at high temperatures produce crystal phases that influence the properties of ceramic products. Calcite exerts a bleaching action on burnt products when added to a formulated mass of clays (in proportions above 5% and less than 30%) and at the same time decreases its expansion by legislation, as it forms crystalline and liquid phases, including cycles temperature and firing adopted. Calcite and dolomite are the most important representatives of carbonates in the ceramic industry. They are used as main components in the manufacture of ceramic tiles with high water absorption. These coatings include "porous coatings" or "tiles." These products are designed or used on walls and are not suitable for application on floors, as they have undesirable technical characteristics, such as mechanical resistance, incompatibility with use. According to Amorós [6], properties of parts of a ceramic product are registered by crystalline phases formed based on calcium and magnesium as ghelenite (SiO2Al2O32CaO) and anortite (2SiO2Al2O3CaO). To achieve these phases, use the dolomite calcium oxide and/or magnesium reaction with

a remaining clay structure proven by its thermal decomposition.

above 1170°C [7].

**2. Clays**

**2.1 Kaolinite**

**84**

**2.2 Montmorillonite**

tion in the ceramic industry.

*Clay Science and Technology*

which may or may not contain impurities [3, 8].

kaolinites usually have low plasticity, see **Figure 1**.

The calculation in general can affect the ceramic product in two ways: low percentages (up to 3%) and high temperature (above 1180°C) result in flow agents, that is, materials that contribute to reduce water absorption and increase the resistance of ceramic products. Above 3%, they can act as a foundation at temperatures

In this chapter, we will highlight properties of limestone clays and their applica-

Clays are hydrated aluminum silicates with crystalline structure arranged in layers, consisting of continuous sheets of SiO4 tetrahedrons, ordered in a hexagonal shape, condensed with octahedral sheets of di and trivalent metal hydroxides, usually below 2 μm. They are materials that in contact with water become plastic, a fundamental characteristic for conformation of ceramic products because it provides mechanical resistance in the pressing, extrusion, or gluing process. Clays are mixtures of various clay minerals such as kaolinite, illite, and montmorillonite,

The kaolinite with structural formula Al2O32SiO22H2O has a dioctahedral structure, which consists of a tetrahedral layer linked by an octahedral layer. Pure

Montmorillonites are a set of family of clay minerals, composed of dioctahedral and trioctahedral silicate sheets, see **Figure 2(a)** and **(b)**. The most outstanding feature of these minerals is their ability to absorb water molecules [8, 9]. It has 80% of exchangeable cations in the galleries and 20% on the lateral surfaces. The modification of montmorillonite clays has aroused scientific and technological interest

*Kaolinite structure. (a) Si*d*O tetrahedra on the bottom half of the layer and Al*d*O,OH octahedra on the top half. (b) Dioctahedral structure.*

### **Figure 2.**

*Crystalline structure of a montmorillonite. (a) Montmorillonite structure, composed of Si, Al, and O. (b) Sheets of dioctahedral and trioctahedral silicates.*

for providing significant improvements when incorporated into pure polymeric materials and conventional composites. The clay modification process occurs preferably through the ionic exchange of the exchangeable cations of its crystalline structure.

### **2.3 Illite**

The basic structural unit of the illites is the same as that of the montmorillonites except that in illites, the silicon atoms in the silica layers are partially replaced by aluminum. Therefore, there are free valences in the boundary layers of the structural units, which are neutralized by K cations, arranged between the overlapping units. The structural scheme of the illites is shown in **Figure 3**. The K cation is the one that best adapts to the hexagonal meshes of the oxygen planes of the layers of silica tetrahedron and is not displaced by other cations. The water adsorption and cation exchange capacity is due only to the broken connections at the ends of the layers. The average diameter of the illites varies between 0.1 and 0.3 μm. When the replacement of silicon in the tetrahedron layers by aluminum in the illites is small, the connections between the structural units provided by the K cations may be deficient and will allow water to enter. When this occurs, the properties of the illites are close to the properties of montmorillonites [3].

### **2.4 Chlorite**

Chlorites are minerals made up of four hydrated aluminum and magnesium silicate layers, containing Fe (II) and Fe (III) as shown in **Figure 4**.

**Figure 3.**

*Crystalline structure of an illite. (a) Silicon atoms in the silica layers partially replaced by aluminum in the illites. (b) Structural scheme of illites.*

• White plastic clays: the clay matrix is kaolinitic, with little illite. They give plasticity to the dough, and after burning they have a white color.

as K2O and Na2O, therefore, with refractory characteristics.

**3.1 Heat action on clays**

*Source: Barba et al. [4].*

*Subgroups of clay minerals.*

**Table 1.**

**Subgroup Chemical**

*Limestone Clays for Ceramic Industry*

Kaolin Xn(Y2O5)(OH)4

Talc XB(Y2O5) (OH)2ZmH2O **species**

*DOI: http://dx.doi.org/10.5772/intechopen.92506*

Chlorite Chlorites Chlorite

**Minerals**

Kaolinites Nacrite (Al2(Si2O5)(OH)4)

Illites Wide variety of minerals

X2n(Y2O5)2(OH)2 [Mg2(Al,Fe(III))(OH)6][Mg3(AlSi3O10)(OH)2]

Montmorillonites Montmorillonites

Dikite (Al2(Si2O5)(OH)4) Livesite (Al2(Si2O5)(OH)4) Halloysite (Al2(Si2O5)(OH)4)

Fe2,22(AlSi3O10)(OH)2Na0,33

(Al1,51Fe0,07Mg0,60)(Al0,28Si3,72)O10(OH)2Na0,33

Hectorite (Mg2,67Li0,33)(Si4O10)(F,OH)2Na0,33 Saponite Mg3(Al0,33Si3,67)O10(OH)2Na0,33

Beidellite (Al1,46Fe0,50Mg0,08)(Al0,36Si3,64)O10(OH)2Na0,4 Nontronite (Fe1,67Mg0,33)(Si4O10)(OH)2Na0,33 and

etc.

**87**

versible, which can be classified as:

• Oxidation of organic matter

• Vitreous phase formation

• Dehydroxylation of the clayey mineral

• Crystallization by increasing the temperature

• Kaolinitic clays: clays of low plasticity and normally free of fluxing oxides such

According to Mackenzie [10], when a ceramic raw material is subjected to the action of heat, it experiences volumetric variations, usually permanent and irre-

• Decomposition of compounds containing oxygen, such as sulfates, carbonates,

• Solid solutions: adjacent crystals of two different materials but of similar

Kaolinitic clay: the scheme according to **Figure 5** shows an endothermic peak

structure can react with each other, forming a solid solution.

between 560 and 590°C referring to the elimination of hydroxyls from the constitution water present in the clays, and an exothermic peak between 980 and

**Figure 4.** *Crystalline structure of chlorite [9].*

The most common clay minerals are interstratified, characteristic of mixtures of clay minerals, classified by subgroup and mineralogical species, see most common classification in **Table 1**. Clay minerals are divided into several classes. A large majority of clays do not have in just one crystalline phase. Two or more chemical species may be present.

### **3. Clays used in the ceramic manufacturing process**

The clays used in the ceramic manufacturing process can be classified into:



*Limestone Clays for Ceramic Industry DOI: http://dx.doi.org/10.5772/intechopen.92506*

**Table 1.** *Subgroups of clay minerals.*


### **3.1 Heat action on clays**

According to Mackenzie [10], when a ceramic raw material is subjected to the action of heat, it experiences volumetric variations, usually permanent and irreversible, which can be classified as:


Kaolinitic clay: the scheme according to **Figure 5** shows an endothermic peak between 560 and 590°C referring to the elimination of hydroxyls from the constitution water present in the clays, and an exothermic peak between 980 and

The most common clay minerals are interstratified, characteristic of mixtures of clay minerals, classified by subgroup and mineralogical species, see most common classification in **Table 1**. Clay minerals are divided into several classes. A large majority of clays do not have in just one crystalline phase. Two or more chemical

*Crystalline structure of an illite. (a) Silicon atoms in the silica layers partially replaced by aluminum in the*

The clays used in the ceramic manufacturing process can be classified into:

• Non-carbonitic clays: they are characterized by the almost total absence of carbonates. The clay minerals present are of the illitic-chloritic type. It has the function of giving plasticity to the dough, and generally after firing they give

• Carbonitic clays: they are formed by associations of illitic-chloritic and eventually illitic-kaolinite clay minerals. The amount of calcium carbonate present can be variable. These clays give the dough plasticity. Generally, after

burning they have colors ranging from beige to orange [4].

**3. Clays used in the ceramic manufacturing process**

species may be present.

*Crystalline structure of chlorite [9].*

**Figure 3.**

**Figure 4.**

**86**

*illites. (b) Structural scheme of illites.*

*Clay Science and Technology*

rise to well-sintered materials.

Carbonates: calcium or magnesium carbonates can appear as coarse or small

completely and the resulting oxides may rehydrate causing expansion according to

Ceramic enamels and frits: can be used in matte enamels as a source of CaO to form crystals such as wollastonite, anorthite, gehlenite or in transparent enamels

Masses for ceramic coating: as a source of CaO up to the limit of 3%, CaCO3 assists in the formation of the vitreous phase. CaO levels that vary from 8 to 14% favor the formation of crystalline phases such as gehlenite, wollastonite, pseudo

Putties for limestone porcelain: calcium carbonates provide the CaO that are

Ceramic pigments: the calcium carbonate provides calcium oxide, which

Glasses: glasses based on NaOH and CaO use CaCO3 in their composition. Obtaining settlement mortars: as a plasticizing agent for water retention and

Sánchez et al. [14] defined some specification parameters for choosing raw

Calcium or magnesium carbonates can appear as coarse or small grains. If they are presented as large grains (>125 μm), they may not react completely, and the

In compositions of ceramic floor covering with low water absorption, CaCO3 acts as a flux until the limit of 3%; above this value, CaCO3 increases porosity and

Stoned ≤3 ≤125 ≤0.3 0.2 20–40 Porous ≤40 ≤125 ≤0.3 0.2 20–40

**Organic matter (%)** **Sulfate content max. (%)**

**IP (%)**

materials for formulations of coating masses, as shown in **Table 2** below.

**Max. particle size of CaCO3 (μm)**

Steel: CaCO3 acts as a flux and pH regulator in water treatment and as lubricant

ð3Þ

grains. If they are presented as large grains (>125 μm), they may not react

**3.3 Use of calcite in the ceramic and chemical industry**

reactions [12, 13].

*Limestone Clays for Ceramic Industry*

*DOI: http://dx.doi.org/10.5772/intechopen.92506*

giving shine.

wollastonite, and anortite.

aggregate incorporation.

for drawing steel rebars.

**Product (%) of**

*IP: index of plasticity.*

**Table 2.**

**89**

**carbonates**

*Specifications for choosing raw materials.*

used as a flux in limestone porcelain masses.

together with SnO2 produces pink pigments.

**3.4 Specifications of raw materials for ceramic tiles**

resulting oxides may rehydrate causing expansion.

can be accepted up to 40% in porous coatings.

**Figure 5.** *Differential thermal analysis of a kaolinitic clay [10].*

**Figure 6.** *Differential thermal analysis of a montmorillonite clay [10].*

1000°C, due to the formation of mullite, which can be represented by the reactions 1 and 2 [8].

$$\underbrace{\text{Al}\_2\text{O}\_3.2\text{SiO}\_2.2\text{H}\_2\text{O}^{580-600}}\_{\text{.}}\text{ Al}\_2\text{O}\_3.2\text{SiO}\_2 + 2\text{ H}\_2\text{O}}\tag{1}$$

$$\text{3(Al}\_2\text{O}\_3.2\text{SiO}\_2) \qquad \overset{\text{380-1000}}{\text{3Al}\_2\text{O}\_3.2\text{SiO}\_2} + 4\text{SiO}\_2 \tag{2}$$

Montmorillonite: montmorillonites have water that lodges in the mineral structure, that is, hydration water of adsorbed ions. The elimination of hydroxyl groups occurs at 700°C. At 850°C, a small endothermic peak may occur due to the loss of montmorillonite crystallinity. Illites can present loss of adsorbed water between 100 and 200°C and water loss in the constitution between 550 and 600°C, see **Figure 6**.

### **3.2 Most common impurities present in clays**

Quartz: it appears in clays in colored or colorless round grains, whose percentage ranges from 0 to 60%. For high levels of quartz, the clay is called sandy and has low plasticity [11].

Hematite: iron can be present in the forms of hematite (α-Fe2O3), goethite (α-FeO�OH), and lemonade (a mixture of iron oxides and hydroxides of a weakly crystalline nature), or simply as Fe3+ ions in the clay structure. In the illite group, Fe3+ ions can replace Al3+ ions in the octahedral structure [11]. Fe2O3 is formed during sintering under oxidation conditions and from minerals in the clays, giving a reddish color to ceramic materials.

Feldspar: feldspars refer to a group of aluminum silicate minerals. The feldspar contained in the clays is a source of sodium and potassium oxides and plays an important role in ceramic materials with quality of flow agents, temperatures such as sintering temperatures, porosity after firing and facilitating phase formation [6]. The most representative are the orthoclase (KAlSi3O8) and albite (NaAlSi3O8).

*Limestone Clays for Ceramic Industry DOI: http://dx.doi.org/10.5772/intechopen.92506*

Carbonates: calcium or magnesium carbonates can appear as coarse or small grains. If they are presented as large grains (>125 μm), they may not react completely and the resulting oxides may rehydrate causing expansion according to reactions [12, 13].

### **3.3 Use of calcite in the ceramic and chemical industry**

Ceramic enamels and frits: can be used in matte enamels as a source of CaO to form crystals such as wollastonite, anorthite, gehlenite or in transparent enamels giving shine.

Masses for ceramic coating: as a source of CaO up to the limit of 3%, CaCO3 assists in the formation of the vitreous phase. CaO levels that vary from 8 to 14% favor the formation of crystalline phases such as gehlenite, wollastonite, pseudo wollastonite, and anortite.

Putties for limestone porcelain: calcium carbonates provide the CaO that are used as a flux in limestone porcelain masses.

Ceramic pigments: the calcium carbonate provides calcium oxide, which together with SnO2 produces pink pigments.

Glasses: glasses based on NaOH and CaO use CaCO3 in their composition.

Obtaining settlement mortars: as a plasticizing agent for water retention and aggregate incorporation.

Steel: CaCO3 acts as a flux and pH regulator in water treatment and as lubricant for drawing steel rebars.

### **3.4 Specifications of raw materials for ceramic tiles**

Sánchez et al. [14] defined some specification parameters for choosing raw materials for formulations of coating masses, as shown in **Table 2** below.

Calcium or magnesium carbonates can appear as coarse or small grains. If they are presented as large grains (>125 μm), they may not react completely, and the resulting oxides may rehydrate causing expansion.

In compositions of ceramic floor covering with low water absorption, CaCO3 acts as a flux until the limit of 3%; above this value, CaCO3 increases porosity and can be accepted up to 40% in porous coatings.


### **Table 2.**

*Specifications for choosing raw materials.*

1000°C, due to the formation of mullite, which can be represented by the reactions

Montmorillonite: montmorillonites have water that lodges in the mineral structure, that is, hydration water of adsorbed ions. The elimination of hydroxyl groups occurs at 700°C. At 850°C, a small endothermic peak may occur due to the loss of montmorillonite crystallinity. Illites can present loss of adsorbed water between 100 and 200°C and water loss in the constitution between 550 and 600°C, see **Figure 6**.

Quartz: it appears in clays in colored or colorless round grains, whose percentage ranges from 0 to 60%. For high levels of quartz, the clay is called sandy and has low

Hematite: iron can be present in the forms of hematite (α-Fe2O3), goethite (α-FeO�OH), and lemonade (a mixture of iron oxides and hydroxides of a weakly crystalline nature), or simply as Fe3+ ions in the clay structure. In the illite group, Fe3+ ions can replace Al3+ ions in the octahedral structure [11]. Fe2O3 is formed during sintering under oxidation conditions and from minerals in the clays, giving a

Feldspar: feldspars refer to a group of aluminum silicate minerals. The feldspar contained in the clays is a source of sodium and potassium oxides and plays an important role in ceramic materials with quality of flow agents, temperatures such as sintering temperatures, porosity after firing and facilitating phase formation [6]. The most representative are the orthoclase (KAlSi3O8) and albite (NaAlSi3O8).

**3.2 Most common impurities present in clays**

reddish color to ceramic materials.

ð1Þ

ð2Þ

1 and 2 [8].

**Figure 6.**

**Figure 5.**

*Clay Science and Technology*

*Differential thermal analysis of a kaolinitic clay [10].*

*Differential thermal analysis of a montmorillonite clay [10].*

plasticity [11].

**88**

Enrique [15] recommends that the CaCO3 particle size should be less than 125 μm, because particles of larger sizes, the CaO resulting from the dissociation of carbonates when calcined at 900°C, do not react with the SiO2 present in the clays and feldspars that should form the pseudo-wollastonite and wollastonite phases, which can give rise to Ca(OH)2 formed by the hydration of CaO, when the part comes into contact with the humidity of the air, generating problems of expansion by humidity, with consequent cracking.

The ceramic tile and brick industry have grown enormously in recent years in Brazil. The clays must have sufficient plasticity to provide mechanical resistance when forming by pressing, in order to guarantee the integrity of the piece in the path between the press and the oven. The feldspar contained in the clays are sources of sodium and potassium oxides, acting as fluxes at temperatures above 800°C for bricks and above 1100°C for ceramic tiles, which facilitates the formation of a vitreous phase and reduces porosity [16, 17].

Quartz is mixed with clay during geological formation. If it is present in a smaller proportion, it helps in the formation of the vitreous phase, in the degassing of organic matter and water. However, large proportions of quartz lead to a drastic reduction in mechanical strength after firing [18]. Iron oxide is present in ceramic raw materials in the form of hematite or goethite, giving the finished product a red color.

The amount of Fe2O3 detected in the samples was between 4.7 and 7.1%. These values are acceptable for use in ceramic tiles, such as bricks and tiles, this element being responsible for the reddish color of the sintered pieces as well as being a powerful flux [20]. The high content of calcium oxide in C4 (12%) and C3 (7%) stands out, characterizing these clays as limestone [21]. C4 clay was previously studied in Alcântara [16], which reports the formation of stains on the ceramic bodies produced with this material, after sintering at 1120°C. This behavior was associated with a high content of CaO, estimated at 10%, which during the burning phase, the dissociation of CaCO3, promotes a high mass loss. C4 (13%) generates many pores, reducing water absorption and resistance of the final product. Thus, the higher the CaO content, the higher the CaCO3 content and in addition, the higher the mass loss. Analyzing the levels of alkaline oxides, it is observed that the sample C2 has the highest concentration of K2O, while the concentration of Na2O is approximately the same in the four samples studied. Alkaline and alkaline earth compounds have a melting effect, which facilitates the formation of liquid phase and linear shrinkage

*Chemical compositions of raw materials by X-ray fluorescence (XRF).*

**Oxide (%) C1 C2 C3 C4** SiO2 63.0 52.1 50.2 45.3 Al2O3 16.7 18.6 15.5 14.1 Fe2O3 4.7 6.8 6.2 7.1 CaO 0.9 2.1 7.2 12.7 K2O 3.8 4.7 3.2 3.2 Na2O 0.6 0.4 0.5 0.7 MgO 1.5 2.3 2.2 2.3 TiO2 0.6 0.8 0.7 0.8 L.O.I 8.2 12.1 14.3 13.8

**Table 4** was arranged according to the increasing amount of CaO present in the clays. Note that C1 and C2 have CaO content below 3%. According to Enrique [15], CaO acts as a flux until the limit of 3% in masses of ceramic coating. The percentage of alkali oxides (Na2O and K2O), also presented in **Table 3**, is another major factor for the densification process, due to the great tendency of liquid phase formation during burning. Considering the sum of the percentages of CaO and alkali oxides in samples C3 and C2, it can be concluded that C2 has a higher proportion of fluxing oxides, suggesting that this sample is the most promising. On the other hand, clays

**Clay CaO (%) Na2O+K2O (%)** C1 0.9 4.4 C2 2.1 5.1 C3 7.2 3.7 C4 12.7 3.9

*Percentage of fluxing oxides in clays determined via XRF measurement.*

during burning [13].

*Source: Santos [19].*

**Table 4.**

**91**

*Source: Santos [19].*

*Limestone Clays for Ceramic Industry*

*DOI: http://dx.doi.org/10.5772/intechopen.92506*

**Table 3.**

Calcite, which appears in most clays used in the production process of ceramic tiles of type BIIb, is a mineral that needs special care in its use due to its high loss to fire. When present in a proportion equal to or less than 3%, this mineral acts as a flux. However, in higher proportions, calcite can cause an increase in the final porosity of the product. In addition, the size of the calcite particle for processing ceramics must be less than 125 μm. For larger sizes, it is observed that the CaO resulting from the dissociation of carbonates can hydrate after burning, promoting variations in the dimension of the piece. Therefore, the use of limestone clays is a challenge, requiring care in processing and control in the formulation and burning of coatings. To ensure the correct sintering of the product, proper grinding and pressing of the raw material are necessary, in addition to efficient, fast burning with the lowest possible energy consumption.

### **4. Characterization of raw materials**

### **4.1 Chemical analysis**

**Table 3** shows the chemical compositions of a typical Brazilian limestone clay used in ceramics [19]. The chemical compositions of the raw materials were determined by X-ray fluorescence spectroscopy by wavelength dispersion (WDFRX), in a Bruker S8 Tiger equipment, in which the percentages of constituent oxides were estimated by the method semi-quantitatively. For these measurements, samples with a mass of 10.0 g were pressed as discs with 40.0 mm diameter and 4.0 mm thickness. During measurements, the samples were kept in a vacuum of 10<sup>6</sup> bar. A mixture of P-10 (90% argon and 10% methane) was used in the proportional counter.

The results show that all clays are composed mainly of SiO2 and Al2O3. These elements are associated with clay minerals, quartz, and feldspar structures [17]. The highest amount of SiO2 was determined for sample C1. This component is important for the manufacture of ceramic tiles, as it improves workability and favors compaction. However, SiO2 can also cause low mechanical strength of sintered ceramic bodies, in addition to reducing shrinkage during firing.

*Limestone Clays for Ceramic Industry*


## *DOI: http://dx.doi.org/10.5772/intechopen.92506*

### **Table 3.**

Enrique [15] recommends that the CaCO3 particle size should be less than 125 μm, because particles of larger sizes, the CaO resulting from the dissociation of carbonates when calcined at 900°C, do not react with the SiO2 present in the clays and feldspars that should form the pseudo-wollastonite and wollastonite phases, which can give rise to Ca(OH)2 formed by the hydration of CaO, when the part comes into contact with the humidity of the air, generating problems of expansion

The ceramic tile and brick industry have grown enormously in recent years in Brazil. The clays must have sufficient plasticity to provide mechanical resistance when forming by pressing, in order to guarantee the integrity of the piece in the path between the press and the oven. The feldspar contained in the clays are sources of sodium and potassium oxides, acting as fluxes at temperatures above 800°C for bricks and above 1100°C for ceramic tiles, which facilitates the formation of a

Quartz is mixed with clay during geological formation. If it is present in a smaller proportion, it helps in the formation of the vitreous phase, in the degassing of organic matter and water. However, large proportions of quartz lead to a drastic reduction in mechanical strength after firing [18]. Iron oxide is present in ceramic raw materials in the form of hematite or goethite, giving the finished product a red

Calcite, which appears in most clays used in the production process of ceramic tiles of type BIIb, is a mineral that needs special care in its use due to its high loss to fire. When present in a proportion equal to or less than 3%, this mineral acts as a flux. However, in higher proportions, calcite can cause an increase in the final porosity of the product. In addition, the size of the calcite particle for processing ceramics must be less than 125 μm. For larger sizes, it is observed that the CaO resulting from the dissociation of carbonates can hydrate after burning, promoting variations in the dimension of the piece. Therefore, the use of limestone clays is a challenge, requiring care in processing and control in the formulation and burning of coatings. To ensure the correct sintering of the product, proper grinding and pressing of the raw material are necessary, in addition to efficient, fast burning with

**Table 3** shows the chemical compositions of a typical Brazilian limestone clay used in ceramics [19]. The chemical compositions of the raw materials were determined by X-ray fluorescence spectroscopy by wavelength dispersion (WDFRX), in a Bruker S8 Tiger equipment, in which the percentages of constituent oxides were estimated by the method semi-quantitatively. For these measurements, samples with a mass of 10.0 g were pressed as discs with 40.0 mm diameter and 4.0 mm thickness. During measurements, the samples were kept in a vacuum of 10<sup>6</sup> bar. A mixture of P-10 (90% argon and 10% methane) was used in the proportional

The results show that all clays are composed mainly of SiO2 and Al2O3. These elements are associated with clay minerals, quartz, and feldspar structures [17]. The highest amount of SiO2 was determined for sample C1. This component is important for the manufacture of ceramic tiles, as it improves workability and favors compaction. However, SiO2 can also cause low mechanical strength of sintered

ceramic bodies, in addition to reducing shrinkage during firing.

by humidity, with consequent cracking.

*Clay Science and Technology*

vitreous phase and reduces porosity [16, 17].

the lowest possible energy consumption.

**4. Characterization of raw materials**

**4.1 Chemical analysis**

counter.

**90**

color.

*Chemical compositions of raw materials by X-ray fluorescence (XRF).*

The amount of Fe2O3 detected in the samples was between 4.7 and 7.1%. These values are acceptable for use in ceramic tiles, such as bricks and tiles, this element being responsible for the reddish color of the sintered pieces as well as being a powerful flux [20]. The high content of calcium oxide in C4 (12%) and C3 (7%) stands out, characterizing these clays as limestone [21]. C4 clay was previously studied in Alcântara [16], which reports the formation of stains on the ceramic bodies produced with this material, after sintering at 1120°C. This behavior was associated with a high content of CaO, estimated at 10%, which during the burning phase, the dissociation of CaCO3, promotes a high mass loss. C4 (13%) generates many pores, reducing water absorption and resistance of the final product. Thus, the higher the CaO content, the higher the CaCO3 content and in addition, the higher the mass loss.

Analyzing the levels of alkaline oxides, it is observed that the sample C2 has the highest concentration of K2O, while the concentration of Na2O is approximately the same in the four samples studied. Alkaline and alkaline earth compounds have a melting effect, which facilitates the formation of liquid phase and linear shrinkage during burning [13].

**Table 4** was arranged according to the increasing amount of CaO present in the clays. Note that C1 and C2 have CaO content below 3%. According to Enrique [15], CaO acts as a flux until the limit of 3% in masses of ceramic coating. The percentage of alkali oxides (Na2O and K2O), also presented in **Table 3**, is another major factor for the densification process, due to the great tendency of liquid phase formation during burning. Considering the sum of the percentages of CaO and alkali oxides in samples C3 and C2, it can be concluded that C2 has a higher proportion of fluxing oxides, suggesting that this sample is the most promising. On the other hand, clays


### **Table 4.** *Percentage of fluxing oxides in clays determined via XRF measurement.*

with a high limestone content, such as C3 and C4, tend to have greater porosity and less mechanical resistance after firing. Additionally, these two raw materials have lower alkaline oxide ratios than those observed for C3 and C2.

### **4.2 X-ray diffractometry**

The X-ray diffraction patterns of the clays are shown in **Figure 7** and correlate positively with the results observed by X-ray fluorescence. The X-ray diffractometry (XRD) technique was used to determine the crystalline phases. The samples were dried in an oven at 110 °C for 24 h, ground, and passed through a 150-μm mesh sieve. The diffraction patterns were obtained in a Rigaku D-MAX 100 equipment, using Cu Kα1 radiation (λ = 1.5418 Å). All measurements were carried out in the continuous scanning mode with speed of 1°/min, in the range of 5 to 65° and in the range of 2 to 15° in samples saturated with ethylene glycol for 1 h to identify montmorillonite by displacing the diffraction peaks at smaller angles compared to dry sample testing. The crystalline phases were identified through Match! (Phase Identification by Powder Diffraction) in the demo version, according to the ICSD (Inorganic Crystal Structure Database).

402PC, under synthetic air flow at 130 ml/min. For these analyses, the samples were compacted in a cylindrical shape, 12.0 mm in length and 6.0 mm in diameter. Under a constant heating rate of 10°C/min, the length of the compacted body is measured as a function of time and temperature, which varied from room temperature to 1150°C. In **Figure 8** we can observe a slight expansion in all curves up to approximately 850°C, and at 573°C, the expansion was more pronounced due to the transformation of α quartz to β [22, 23], except for C2, which presents a lower percentage of free quartz. From 573°C, there was a gradual reduction in the expansion rate, occurring

**Minerals (%) C1 C2 C3 C4** Quartz 55.7 51.8 65.1 57.1 Kaolinite 6.3 10.7 7.4 5.5 Muscovite 11.8 14.0 11.2 12.1 Montmorillonite 5.6 4.9 4.6 6.7 Calcite 8.6 2.8 1.1 13.7 Feldspar 6.3 9.9 6.2 3.2 Hematite 5.7 5.9 4.4 1.7

The results shown in **Table 5** with the percentages of CaO, Na2O, and K2O recommended by XRF measurements point out that sample C2 has a greater amount of funds (calcium carbonate up to a limit of 3% and alkaline oxides), or what is known as a greater linear shrinkage. Despite its advantages over the other samples, the C2 clay underwent deformation during firing up to 1150°C. This effect, known as pyroplastic deformation, may be due to the large proportion of funds in the sample, a high content of Fe2O3, and, even, the amount of organic matter [24]. One of the ways to control deformation during firing is to adjust the thermal cycle

or starting with sintering, followed by an exponential retraction [22].

*Mineralogical compositions of clays determined by XRD.*

*Limestone Clays for Ceramic Industry*

*DOI: http://dx.doi.org/10.5772/intechopen.92506*

**Table 5.**

**Figure 8.**

**93**

*Dilatometric curves of clays at a heating rate of 10°C/min [19].*

The main phases identified were quartz, kaolinite, muscovite, montmorillonite, calcite, feldspar, and hematite. Minerals from kaolinite and montmorillonite clay were identified in all analyzed clays. According to Celik [20], these clay minerals provide the necessary plasticity to guarantee conformation through the pressing process. The percentage of each crystalline phase present in the samples was estimated from the relative intensity of the main peaks in each phase. The values are shown in **Table 5**. The percentage of carbonates increases from 0.9% in C1 to 12.4% in C4.

### **4.3 Dilatometric tests**

To verify the dimensional changes of expansion and thermal retraction of the samples, dilatometry tests were performed on a Netzsch dilatometer, model DIL

**Figure 7.** *X-ray diffraction patterns of the clays [19].*

### *Limestone Clays for Ceramic Industry DOI: http://dx.doi.org/10.5772/intechopen.92506*


### **Table 5.**

with a high limestone content, such as C3 and C4, tend to have greater porosity and less mechanical resistance after firing. Additionally, these two raw materials have

The X-ray diffraction patterns of the clays are shown in **Figure 7** and correlate positively with the results observed by X-ray fluorescence. The X-ray diffractometry (XRD) technique was used to determine the crystalline phases. The samples were dried in an oven at 110 °C for 24 h, ground, and passed through a 150-μm mesh sieve. The diffraction patterns were obtained in a Rigaku D-MAX 100 equipment, using Cu Kα1 radiation (λ = 1.5418 Å). All measurements were carried out in the continuous scanning mode with speed of 1°/min, in the range of 5 to 65° and in the range of 2 to 15° in samples saturated with ethylene glycol for 1 h to identify montmorillonite by displacing the diffraction peaks at smaller angles compared to dry sample testing. The crystalline phases were identified through Match! (Phase Identification by Powder Diffraction) in the demo version, according to the

The main phases identified were quartz, kaolinite, muscovite, montmorillonite, calcite, feldspar, and hematite. Minerals from kaolinite and montmorillonite clay were identified in all analyzed clays. According to Celik [20], these clay minerals provide the necessary plasticity to guarantee conformation through the pressing process. The percentage of each crystalline phase present in the samples was estimated from the relative intensity of the main peaks in each phase. The values are shown in **Table 5**.

To verify the dimensional changes of expansion and thermal retraction of the samples, dilatometry tests were performed on a Netzsch dilatometer, model DIL

The percentage of carbonates increases from 0.9% in C1 to 12.4% in C4.

lower alkaline oxide ratios than those observed for C3 and C2.

**4.2 X-ray diffractometry**

*Clay Science and Technology*

**4.3 Dilatometric tests**

**Figure 7.**

**92**

*X-ray diffraction patterns of the clays [19].*

ICSD (Inorganic Crystal Structure Database).

*Mineralogical compositions of clays determined by XRD.*

402PC, under synthetic air flow at 130 ml/min. For these analyses, the samples were compacted in a cylindrical shape, 12.0 mm in length and 6.0 mm in diameter. Under a constant heating rate of 10°C/min, the length of the compacted body is measured as a function of time and temperature, which varied from room temperature to 1150°C.

In **Figure 8** we can observe a slight expansion in all curves up to approximately 850°C, and at 573°C, the expansion was more pronounced due to the transformation of α quartz to β [22, 23], except for C2, which presents a lower percentage of free quartz. From 573°C, there was a gradual reduction in the expansion rate, occurring or starting with sintering, followed by an exponential retraction [22].

The results shown in **Table 5** with the percentages of CaO, Na2O, and K2O recommended by XRF measurements point out that sample C2 has a greater amount of funds (calcium carbonate up to a limit of 3% and alkaline oxides), or what is known as a greater linear shrinkage. Despite its advantages over the other samples, the C2 clay underwent deformation during firing up to 1150°C. This effect, known as pyroplastic deformation, may be due to the large proportion of funds in the sample, a high content of Fe2O3, and, even, the amount of organic matter [24]. One of the ways to control deformation during firing is to adjust the thermal cycle

**Figure 8.** *Dilatometric curves of clays at a heating rate of 10°C/min [19].*

through the dilatometric curves, so that the plate remains within the required standards [25].

intense endothermic peak of approximately 35–44% of the mass loss can be observed in differential thermal analysis. In ternary diagrams, it is observed that there is a eutectic point (above 1170°C), which reduces the dimensional stability in

Clays when mixed with limestone can behave differently, as shown by Sánchez [25]. **Figure 10** shows a standard clay with 5 and 10% of incorporated limestone. It was observed that as the limestone and temperature increase, respectively, the dimensional instability increases. In other words, the retraction increases constantly, when it undergoes an exponential increase, reaching the melting point. This phenomenon can be explained as follows: when exhibiting CaO up to the limit of 3%, this, associated with SiO2 and Al2O3 present in clays and feldspars,

ceramic products, which can melt quickly (**Figure 9**).

*Limestone Clays for Ceramic Industry*

*DOI: http://dx.doi.org/10.5772/intechopen.92506*

**Figure 11.**

**Figure 12.**

**95**

*Scanning electron microscopy of a ceramic with 10% of CaO.*

*Firing curve of a calcite clay.*

### **4.4 Firing clays with limestone**

Clays containing limestone when subjected to burning, CaCO3 after heating, in the temperature range between 850 and 920°C, form CaO and release CO2. An

**Figure 9.** *Ternary diagram of CaO, SiO2, and Al2O3.*

**Figure 10.** *Ceramic coating mass with incorporated calcite waste.*

### *Limestone Clays for Ceramic Industry DOI: http://dx.doi.org/10.5772/intechopen.92506*

through the dilatometric curves, so that the plate remains within the required

Clays containing limestone when subjected to burning, CaCO3 after heating, in the temperature range between 850 and 920°C, form CaO and release CO2. An

standards [25].

*Clay Science and Technology*

**Figure 9.**

**Figure 10.**

**94**

*Ternary diagram of CaO, SiO2, and Al2O3.*

*Ceramic coating mass with incorporated calcite waste.*

**4.4 Firing clays with limestone**

intense endothermic peak of approximately 35–44% of the mass loss can be observed in differential thermal analysis. In ternary diagrams, it is observed that there is a eutectic point (above 1170°C), which reduces the dimensional stability in ceramic products, which can melt quickly (**Figure 9**).

Clays when mixed with limestone can behave differently, as shown by Sánchez [25]. **Figure 10** shows a standard clay with 5 and 10% of incorporated limestone. It was observed that as the limestone and temperature increase, respectively, the dimensional instability increases. In other words, the retraction increases constantly, when it undergoes an exponential increase, reaching the melting point.

This phenomenon can be explained as follows: when exhibiting CaO up to the limit of 3%, this, associated with SiO2 and Al2O3 present in clays and feldspars,

**Figure 11.** *Firing curve of a calcite clay.*

**Figure 12.** *Scanning electron microscopy of a ceramic with 10% of CaO.*

helps in the formation of eutectic systems at 1170°C, with consequent formation of liquid phase and contributing to obtain the desired mechanical strength and porosity. When introduced in percentages above 4%, CaCO3 levels are increased, and the composition moves from the eutectic line, forming crystalline phases such as CaSiO3 (pseudo-wollastonite) and 2CaOAl2O3SiO2 (gehlenite). So, a larger number of pores is left by the eliminated CO2. In this way, the porosity of the final product is increased, as shown in **Figure 11**. In **Figure 12** is shown a photo of a clay mass with 10% calibration in which the porosity exerted can be observed.

**References**

2009;**47**:204-207

Portuguese)

Editrice; 1979

319-342

**97**

[1] Teixeira SR, Souza SA, Moura CAI. Mineralogical characterization of clays used in the structural ceramics industry in west of S. Paulo, Brazil. Cerâmica.

*DOI: http://dx.doi.org/10.5772/intechopen.92506*

*Limestone Clays for Ceramic Industry*

[12] Cargnin M, Souza SMAG, Souza AAU, Noni AJ. Determinação de parâmetros cinéticos da sinterização de

monoqueima do tipo BIIa. Cerâmica.

[13] López SYR, Rodriguez JS, Sueyoshi SS. Determination of the activation energy for densification of porcelain stoneware. Journal of Ceramic Processing Research. 2011;**12**:228

[14] Sánchez E, Ortz MJ, García-Tem J, Cantavella V. Efeito da Composição das Matérias-Primas Empregadas na

Fabricação de Grês Porcelanato sobre as Fases Formadas Durante a Queima e as

[15] Enrique EJ et al. Decomposición de Carbonatos durante la Cocción de Piezas de Revestimento Cerámico Vidriado. Relacion com La Aparición de Pinchados. Qualicer; 1998

[16] Alcântara AC, Beltrão MS, Oliveira

HA, Gimenez IF, Barreto LS. Characterization of ceramic tiles prepared from two clays from Sergipe-Brazil. Applied Clay Science. 2008;**39**

[17] Dondi M, Guarani I, Ligas GP, Palomba M, Raimondo M, Uras I. Chemical, mineralogical and ceramic properties of kaolinitic materials from the Tresnuraghes mining district (Western Sardinia, Italy). Applied Clay

[18] Seynou UM, Millogo Y, Ouedraogo

transformations and properties of tiles from a clay from Burkina Faso. Applied

Science. 2010;**18**:145

J, Traor RK, Tirlocq J. Firing

Clay Science. 2011;**51**:499

[19] Santos CP. Study of process variables and sinterization kinetics of materials used in the production of ceramic coatings [PhD thesis]. Brazil:

Propriedades do Produto Final. Cerâmica Industrial. 2001;**6**:15-22

revestimentos cerâmicos de

2011;**57**:461-467

[2] Vieira CMF, Monteiro SN, Dualibi FH. Consideraçoes sobre o uso da grunlometia como parâmetro de controle de uma argila sedimentar. Cerâmica Indusrial. 2005;**10**:23-26

[3] Gomes CF. Argilas o que são e para que servem. Lisboa, Portugal: Fundação

[4] Barba A et al. Materias Primas para la fabricación de suportes de baldosas cerámicas. 2nd ed. Castellón, Espanha: Instituto de Tecnologia cerâmica - ITC

Calouste Gulbenkian; 1988. (in

AICE; Castanèda; 2002. p. 292

[5] Padoa L. La Cottura dei Prodotti Ceramic. Vol. 65. Faenza: Faenza

[6] Castro RJS. Estudo do efeito do feldspato e resíduo de caulim na produção de revestimento cerâmico. Cerâmica Industrial. 2015;**20**(1):30

[7] Singer F, Singer S. Industrial Ceramics. USA: Chapmann Hall; 1995

[8] Santos PS. Tecnologia de Argilas. São Paulo: Editora Edgard Blücher; 1989

[9] Barba A et al. Materias primas para la fabricación de soportes de baldosas cerámicas. Espanha: Editora ITC instituto de tecnologia cerámica; 1997

[10] Mackenzie CR. The Differential Thermal Investigation of Clays. Londres: Editorial Cambridge; 1959

[11] Stepkowska E, Jefferis S. Influence of microstructure on firing color of clays. Applied Clay Science. 1992;**6**:

### **5. Conclusions and perspectives**

Limestone is a contaminant for clay that above 125 μm can cause expansion and consequently cracks.

Rapid tests that mix clay with HCl can promote effervescence due to the release of CO2 and contribute to decrease the amount of limestone.

In the ceramic industry, wet grinding of components is carried out in ball mills and grinding will be more efficient if the sieves are 150 to 325 μm. In ceramic mass formulations, the amount of CaO up to 3% contributes to the formation of the vitreous phase, however, between 8 and 14%, it favors the formation of crystalline phases, reducing the absorption of water and increasing the mechanical resistance.

### **Author details**

Herbet Alves de Oliveira<sup>1</sup> \* and Cochiran Pereira dos Santos<sup>2</sup>


\*Address all correspondence to: herbetalves148@gmail.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Limestone Clays for Ceramic Industry DOI: http://dx.doi.org/10.5772/intechopen.92506*

### **References**

helps in the formation of eutectic systems at 1170°C, with consequent formation of liquid phase and contributing to obtain the desired mechanical strength and porosity. When introduced in percentages above 4%, CaCO3 levels are increased, and the composition moves from the eutectic line, forming crystalline phases such as CaSiO3 (pseudo-wollastonite) and 2CaOAl2O3SiO2 (gehlenite). So, a larger number of pores is left by the eliminated CO2. In this way, the porosity of the final product is increased, as shown in **Figure 11**. In **Figure 12** is shown a photo of a clay

Limestone is a contaminant for clay that above 125 μm can cause expansion and

Rapid tests that mix clay with HCl can promote effervescence due to the release

In the ceramic industry, wet grinding of components is carried out in ball mills and grinding will be more efficient if the sieves are 150 to 325 μm. In ceramic mass formulations, the amount of CaO up to 3% contributes to the formation of the vitreous phase, however, between 8 and 14%, it favors the formation of crystalline phases, reducing the absorption of water and increasing the mechanical resistance.

\* and Cochiran Pereira dos Santos<sup>2</sup>

2 Physics Department, Federal University of Sergipe, São Cristóvão, SE, Brazil

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

mass with 10% calibration in which the porosity exerted can be observed.

of CO2 and contribute to decrease the amount of limestone.

**5. Conclusions and perspectives**

consequently cracks.

*Clay Science and Technology*

**Author details**

**96**

Herbet Alves de Oliveira<sup>1</sup>

1 Federal Institute of Sergipe, Estância, SE, Brazil

provided the original work is properly cited.

\*Address all correspondence to: herbetalves148@gmail.com

[1] Teixeira SR, Souza SA, Moura CAI. Mineralogical characterization of clays used in the structural ceramics industry in west of S. Paulo, Brazil. Cerâmica. 2009;**47**:204-207

[2] Vieira CMF, Monteiro SN, Dualibi FH. Consideraçoes sobre o uso da grunlometia como parâmetro de controle de uma argila sedimentar. Cerâmica Indusrial. 2005;**10**:23-26

[3] Gomes CF. Argilas o que são e para que servem. Lisboa, Portugal: Fundação Calouste Gulbenkian; 1988. (in Portuguese)

[4] Barba A et al. Materias Primas para la fabricación de suportes de baldosas cerámicas. 2nd ed. Castellón, Espanha: Instituto de Tecnologia cerâmica - ITC AICE; Castanèda; 2002. p. 292

[5] Padoa L. La Cottura dei Prodotti Ceramic. Vol. 65. Faenza: Faenza Editrice; 1979

[6] Castro RJS. Estudo do efeito do feldspato e resíduo de caulim na produção de revestimento cerâmico. Cerâmica Industrial. 2015;**20**(1):30

[7] Singer F, Singer S. Industrial Ceramics. USA: Chapmann Hall; 1995

[8] Santos PS. Tecnologia de Argilas. São Paulo: Editora Edgard Blücher; 1989

[9] Barba A et al. Materias primas para la fabricación de soportes de baldosas cerámicas. Espanha: Editora ITC instituto de tecnologia cerámica; 1997

[10] Mackenzie CR. The Differential Thermal Investigation of Clays. Londres: Editorial Cambridge; 1959

[11] Stepkowska E, Jefferis S. Influence of microstructure on firing color of clays. Applied Clay Science. 1992;**6**: 319-342

[12] Cargnin M, Souza SMAG, Souza AAU, Noni AJ. Determinação de parâmetros cinéticos da sinterização de revestimentos cerâmicos de monoqueima do tipo BIIa. Cerâmica. 2011;**57**:461-467

[13] López SYR, Rodriguez JS, Sueyoshi SS. Determination of the activation energy for densification of porcelain stoneware. Journal of Ceramic Processing Research. 2011;**12**:228

[14] Sánchez E, Ortz MJ, García-Tem J, Cantavella V. Efeito da Composição das Matérias-Primas Empregadas na Fabricação de Grês Porcelanato sobre as Fases Formadas Durante a Queima e as Propriedades do Produto Final. Cerâmica Industrial. 2001;**6**:15-22

[15] Enrique EJ et al. Decomposición de Carbonatos durante la Cocción de Piezas de Revestimento Cerámico Vidriado. Relacion com La Aparición de Pinchados. Qualicer; 1998

[16] Alcântara AC, Beltrão MS, Oliveira HA, Gimenez IF, Barreto LS. Characterization of ceramic tiles prepared from two clays from Sergipe-Brazil. Applied Clay Science. 2008;**39**

[17] Dondi M, Guarani I, Ligas GP, Palomba M, Raimondo M, Uras I. Chemical, mineralogical and ceramic properties of kaolinitic materials from the Tresnuraghes mining district (Western Sardinia, Italy). Applied Clay Science. 2010;**18**:145

[18] Seynou UM, Millogo Y, Ouedraogo J, Traor RK, Tirlocq J. Firing transformations and properties of tiles from a clay from Burkina Faso. Applied Clay Science. 2011;**51**:499

[19] Santos CP. Study of process variables and sinterization kinetics of materials used in the production of ceramic coatings [PhD thesis]. Brazil: Federal University of Sergipe; 2016. Available from: https://ri.ufs.br/bitstrea m/riufs/3466/1/COCHIRAN\_PEREIRA\_ SANTOS.pdf

[20] Celik H. Technological characterization and industrial application of two Turkish clays for the ceramic industry. Applied Clay Science. 2010;**50**:245

[21] Gonzalez F, Romero V, Garcia G, Gonzalez M. Firing transformations of mixtures of clays containing illite, kaolinite and calcium carbonate used by ornamental tile industries. Applied Clay Science. 1990;**5**:361

[22] Salem A, Jazayeri SH, Rastelli E, Timellini G. Dilatometric study of shrinkage during sintering process for porcelain stoneware body in presence of nepheline syenite. Journal of Materials Processing Technology. 2009;**209**:1240

[23] Zaied FH, Abidi R, Slim-Shimi N, Somarin AK. Potentiality of clay raw materials from Gram area (Northern Tunisia) in the ceramic industry. Applied Clay Science. 2015;**1**:112-113

[24] Amorós JL. Manual para el control de la calidad de materias primas arcillosas. 1ª Edición ed. Castellón, Espanha: Instituto de Tecnología Cerámica - AICE; 1998

[25] Prado ACA, Zanardo A, Moreno MMT, Menegazzo APM. Reduced susceptibility to pyroplastic deformation of clay at the Santa Gertrudes ceramic pole through the addition of raw materials. Cerâmica. 2008;**54**:7-11

**99**

**Chapter 6**

**Abstract**

**1. Introduction**

Multifunctional Clay in

*Unnikrishnan-Meenakshi Dhanalekshmi,* 

*Sekar Krishnaraj, Yogeeswarakannan Harish Sundar,* 

*Nagarajan Sri Durga Devi and Irisappan Sarathchandiran*

Clay has its widespread applications in pharmaceuticals from ancient world to modern era. It is one of the excellent excipients present in the commercially available pharmaceuticals. Its use in many of dosage forms viz. in suspension, emulsion, ointments, gels, tablet and as drug delivery carrier as suspending agent, emulsifying agent, stiffening agent, binder, diluent, opacifier, and as release retardant have been explored in many studies. Variety of minerals is used as both excipient and as an active ingredient; among that kaolinite, talc, and gypsum are important. Their inertness, low toxicity, versatile physiochemical properties and cost effectiveness has increased its usage in pharma industries. Many minerals have its own pharmacological action as antacid, anti-bacterial, anti-emetic, anti- diarrheal agent and as skin protectant etc. Their unique structure which helps them to absorb material onto their layered sheets has opened a wide variety of applications in drug delivery. The understanding of surface chemistry and particle size distribution of clay minerals has led the pharmaceutical field in many directions and future perspectives.

**Keywords:** pharmaceutics, active pharmaceutical ingredient, excipients, inherent

Usage of clay in medicine dates back to prehistorian era. Their evidences are present throughout the history from the clay pots of Nippur, Mesopotamia which gave the evidence of using clay against hemorrhages, the book "papyrus ebers" dating back in 1600 BC provided the details of using clay-based medicine for certain diseases. Many vital information on medical clay is mentioned in "On Airs, Waters and Places" written by Hippocrates (460–377 BC). One of the notable healing clay used in medicine during early days is known as Armenian bole (*bolus armenus*). They are pharmacologically used for the treatment of diarrhea, dysentery, hemorrhage, even as an astringent in few cases. Avicena in his book "El Canon" classified various types of clay and their internal and external applications. He also mentioned their role in anti-poison treatment and rheumatic disorders. Even though their consumption has been subjected to lot of questions the practice of using medicinal and edible clay prevails till date for their curative and beneficial effects.

medicinal properties, drug delivery carrier, synergistic effect

Pharmaceuticals

*Nandakumar Selvasudha,* 

### **Chapter 6**

Federal University of Sergipe; 2016. Available from: https://ri.ufs.br/bitstrea m/riufs/3466/1/COCHIRAN\_PEREIRA\_

application of two Turkish clays for the ceramic industry. Applied Clay Science.

[21] Gonzalez F, Romero V, Garcia G, Gonzalez M. Firing transformations of mixtures of clays containing illite, kaolinite and calcium carbonate used by ornamental tile industries. Applied Clay

[22] Salem A, Jazayeri SH, Rastelli E, Timellini G. Dilatometric study of shrinkage during sintering process for porcelain stoneware body in presence of nepheline syenite. Journal of Materials Processing Technology. 2009;**209**:1240

[23] Zaied FH, Abidi R, Slim-Shimi N, Somarin AK. Potentiality of clay raw materials from Gram area (Northern Tunisia) in the ceramic industry. Applied Clay Science. 2015;**1**:112-113

[24] Amorós JL. Manual para el control de la calidad de materias primas arcillosas. 1ª Edición ed. Castellón, Espanha: Instituto de Tecnología

[25] Prado ACA, Zanardo A, Moreno MMT, Menegazzo APM. Reduced susceptibility to pyroplastic deformation of clay at the Santa Gertrudes ceramic pole through the addition of raw materials. Cerâmica.

Cerámica - AICE; 1998

2008;**54**:7-11

**98**

[20] Celik H. Technological characterization and industrial

*Clay Science and Technology*

SANTOS.pdf

2010;**50**:245

Science. 1990;**5**:361

## Multifunctional Clay in Pharmaceuticals

*Nandakumar Selvasudha,* 

*Unnikrishnan-Meenakshi Dhanalekshmi, Sekar Krishnaraj, Yogeeswarakannan Harish Sundar, Nagarajan Sri Durga Devi and Irisappan Sarathchandiran*

### **Abstract**

Clay has its widespread applications in pharmaceuticals from ancient world to modern era. It is one of the excellent excipients present in the commercially available pharmaceuticals. Its use in many of dosage forms viz. in suspension, emulsion, ointments, gels, tablet and as drug delivery carrier as suspending agent, emulsifying agent, stiffening agent, binder, diluent, opacifier, and as release retardant have been explored in many studies. Variety of minerals is used as both excipient and as an active ingredient; among that kaolinite, talc, and gypsum are important. Their inertness, low toxicity, versatile physiochemical properties and cost effectiveness has increased its usage in pharma industries. Many minerals have its own pharmacological action as antacid, anti-bacterial, anti-emetic, anti- diarrheal agent and as skin protectant etc. Their unique structure which helps them to absorb material onto their layered sheets has opened a wide variety of applications in drug delivery. The understanding of surface chemistry and particle size distribution of clay minerals has led the pharmaceutical field in many directions and future perspectives.

**Keywords:** pharmaceutics, active pharmaceutical ingredient, excipients, inherent medicinal properties, drug delivery carrier, synergistic effect

### **1. Introduction**

Usage of clay in medicine dates back to prehistorian era. Their evidences are present throughout the history from the clay pots of Nippur, Mesopotamia which gave the evidence of using clay against hemorrhages, the book "papyrus ebers" dating back in 1600 BC provided the details of using clay-based medicine for certain diseases. Many vital information on medical clay is mentioned in "On Airs, Waters and Places" written by Hippocrates (460–377 BC). One of the notable healing clay used in medicine during early days is known as Armenian bole (*bolus armenus*). They are pharmacologically used for the treatment of diarrhea, dysentery, hemorrhage, even as an astringent in few cases. Avicena in his book "El Canon" classified various types of clay and their internal and external applications. He also mentioned their role in anti-poison treatment and rheumatic disorders. Even though their consumption has been subjected to lot of questions the practice of using medicinal and edible clay prevails till date for their curative and beneficial effects.

### *Clay Science and Technology*

Their usage in pharmaceutical industry is invariable due to their versatile property; they are used in almost every formulation like tropical to oral and also as an excipient. As the scientific community grows, there have been many papers published to support the medicinal and curative benefits of clay minerals [1–8].

The important component of clay is the clay minerals but it also comprises of associated minerals, organic, and inorganic materials. Clay can be grouped based on the geological aspects such as


Each clay has their own properties to distinguish themselves from the other. The classification also extends based on their geometrical shape, arrangement, and their usage. The classifications are given below.

Based on the geometry of the clay, it has been classified into four major groups and the subgroups are specified in **Table 1**.


The variation is due to the arrangement of tetrahedral and octahedral sheets, where kaolinite group has one tetrahedral sheet arranged over one octahedral sheet


**101**

**2. Use of clay as excipients**

*Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

*Classification and usage of clay minerals.*

**Figure 1.**

whereas two tetrahedral sheets arranged over one octahedral sheet in smectite group. In case of chlorite group, octahedral sheet is arranged adjacent to 2:1 layer. The clay minerals exhibit versatile properties such as high adsorption capacity, chemical inertness, thixotropy, specific surface area, ion exchange capacity, less toxicity for oral administration, swelling property justifying their wide applications in pharmaceutical industries as excipient to enhance the physiochemical and organoleptic characteristics of a drug. It also helps in aiding drug conservation, elaboration, liberation of drug into the organism. These are achieved by incorporating the clay minerals such as disintegrates, lubricants, opacifiers, binders, diluents, isotonic agent, anti-caking agents, emulsifying agent, desiccant, thickening agent, and flavor modulators. Apart from the pharmaceutical applications, clay minerals also possess a lot of pharmacological properties like anti-bacterial, anti-viral, anti-diarrheal, gastro-intestinal protector, skin protection, and a potent detoxifier. The future trend holds for the MDDS using nano-clay minerals due to their inertness and biocompatibility. More details about the pharmaceutical and pharmacological uses of clay minerals and their advancement in drug delivery system have been discussed in the following sections. Further the classification and usage of clay minerals is illustrated in **Figure 1**.

An excipient is an inert additive ingredient formulated along with active compound to enhance its organoleptic, physiochemical properties. Clay has been used for almost every type of excipients (**Table 2**). Though several investigations showed that clay interacts with the drug molecule conversely to the nature of excipients, the interaction may hinder the drug bioavailability inside the body. The co-administration of montmorillonite leads to the degradation of certain cardiovascular tonic [9], anti-inflammatory drug [10]. Similarly, palygorskite and sepiolite degraded hydrocortisone and dexamethasone [11, 12]. Certain clay also affects the chemical stability of diazepam. Drugs such as phenobarbital sodium, diazepam solution, and lansoprazole show interaction with magnesite. Bioavailabity of tetracycline, indomethacin, aspirin, aspartame, ampicillin, cephalexin, and erythromycin has been drastically affected by calcium rich minerals. Clay minerals has also shown tendency to affect the drug liberation by interacting with the drugs through various mechanisms. They have shown to affect the liberation of amphetamines, analgesics, antibiotics, anxiolytics, solar protectors, and anti-histamines [13–16]. The adsorption of anti-histamines, antibiotics, atropine

**Table 1.** *Subgroups of the clay.* *Clay Science and Technology*

the geological aspects such as

• Special clay

• Common clay

• Refractory clay

• Modified clay

• Nano clay

1.Kaolinite

2.Smectite

4.Chlorite

3.Illite

• Primary or residual clay

• Secondary or sedimentary clay

usage. The classifications are given below.

and the subgroups are specified in **Table 1**.

3 Montmorillonate (Al1.67Mg0.33)

7 (Mg,AL,Fe3+)5(Si,Al)8O20(OH)2(OH2)4.4H2O

Si4O10(OH)2M + 0.33 Saponite:Mg3(Si3.67Al0.33)O10(OH)2M + 0.33 Hectorite(MgLi)3(SiAl)4O10(OH)2M+

Mg8Si12O30(OH)4(OH2)4.8H2O

Their usage in pharmaceutical industry is invariable due to their versatile property; they are used in almost every formulation like tropical to oral and also as an excipient. As the scientific community grows, there have been many papers published to

The important component of clay is the clay minerals but it also comprises of associated minerals, organic, and inorganic materials. Clay can be grouped based on

Each clay has their own properties to distinguish themselves from the other. The classification also extends based on their geometrical shape, arrangement, and their

Based on the geometry of the clay, it has been classified into four major groups

The variation is due to the arrangement of tetrahedral and octahedral sheets, where kaolinite group has one tetrahedral sheet arranged over one octahedral sheet

**S. No General formula Group Layer type**  1 Al2Si2O5(OH) Kaolinite-Serpentine 1:1 2 Al2Si4O10(OH)2Mg3Si4O10(OH)2 Pyrophyllitetalc 2:1

4 (Mg,Fe,Al)3(Al,Si)4O10(OH)2.4H2O Vermiculite 2:1 5 KAl2(Si3Al)O10(OH)2 Mica/Illite 2:1 6 Al4[Si8O20](OH)4Al4(OH)12 Chlorite 2:1:1

Smectite 2:1

Palygorskitesepiolite group

support the medicinal and curative benefits of clay minerals [1–8].

**100**

**Table 1.**

*Subgroups of the clay.*

**Figure 1.** *Classification and usage of clay minerals.*

whereas two tetrahedral sheets arranged over one octahedral sheet in smectite group. In case of chlorite group, octahedral sheet is arranged adjacent to 2:1 layer. The clay minerals exhibit versatile properties such as high adsorption capacity, chemical inertness, thixotropy, specific surface area, ion exchange capacity, less toxicity for oral administration, swelling property justifying their wide applications in pharmaceutical industries as excipient to enhance the physiochemical and organoleptic characteristics of a drug. It also helps in aiding drug conservation, elaboration, liberation of drug into the organism. These are achieved by incorporating the clay minerals such as disintegrates, lubricants, opacifiers, binders, diluents, isotonic agent, anti-caking agents, emulsifying agent, desiccant, thickening agent, and flavor modulators. Apart from the pharmaceutical applications, clay minerals also possess a lot of pharmacological properties like anti-bacterial, anti-viral, anti-diarrheal, gastro-intestinal protector, skin protection, and a potent detoxifier. The future trend holds for the MDDS using nano-clay minerals due to their inertness and biocompatibility. More details about the pharmaceutical and pharmacological uses of clay minerals and their advancement in drug delivery system have been discussed in the following sections. Further the classification and usage of clay minerals is illustrated in **Figure 1**.

### **2. Use of clay as excipients**

An excipient is an inert additive ingredient formulated along with active compound to enhance its organoleptic, physiochemical properties. Clay has been used for almost every type of excipients (**Table 2**). Though several investigations showed that clay interacts with the drug molecule conversely to the nature of excipients, the interaction may hinder the drug bioavailability inside the body. The co-administration of montmorillonite leads to the degradation of certain cardiovascular tonic [9], anti-inflammatory drug [10]. Similarly, palygorskite and sepiolite degraded hydrocortisone and dexamethasone [11, 12]. Certain clay also affects the chemical stability of diazepam. Drugs such as phenobarbital sodium, diazepam solution, and lansoprazole show interaction with magnesite. Bioavailabity of tetracycline, indomethacin, aspirin, aspartame, ampicillin, cephalexin, and erythromycin has been drastically affected by calcium rich minerals. Clay minerals has also shown tendency to affect the drug liberation by interacting with the drugs through various mechanisms. They have shown to affect the liberation of amphetamines, analgesics, antibiotics, anxiolytics, solar protectors, and anti-histamines [13–16]. The adsorption of anti-histamines, antibiotics, atropine


### **Table 2.**

*Application of clay minerals as excipient.*

sulfate, salicylate, hyoscyamine, hydrobromide, paracetamol, and chloroquine into periclase and brucite has been showed by Khalil et al. [15]. These interactions have been proven useful since they are used to retard drug release. So they aid in controlled drug release and improve the Tmax considerably.

### **2.1 Clay in biphasic liquid formulation**

### *2.1.1 In suspension*

Excipients are required in the biphasic system in order to obtain proper wetting and to maintain stability of the formulation. In order to overcome the

**103**

viscosity [28].

*Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

tion at 1.7% w/v of bentonite.

hydrophobicity of the drug and to aid in dispersion, clay minerals are added to the suspension as wetting agent. Sulfur ointment is prepared by blending kaolin with sulfur dispersed in oil phase [17]. The usage of bentonite as a wetting agent in foundation creams is also documented [18]. The clay also helps to maintain the stability by acting as suspending and anti-caking agent. They prevent sedimentation, changes in dispersion property, and flocculation. The criteria of selection of suitable suspending agent depend on compatibility, appearance, source, cost, and pH tolerance. The properties of the suspending agent including high viscosity at low shear rate, temperature, and storage tolerance, should not be affected by electrolyte or pH and be non-toxic. The formation of aggregates which in turn leads to the caking of solids would be the problem of suspension at the higher concentration. Reduction in the particle size or viscosity could not prevent caking. Caking can be prevented by flocculation and electrostatic stabilization [19, 20]. Kibbe showed that the increase in the stability of suspension using kaolin and talc as suspending and anti-caking agent. A suspension of pectin containing MAS dispersed in water along with kaolin under constant agitation at 70°C to which pectin was added, CMC was used to modify viscosity [17]. The usage of MAS and its four types (IA, IB, IC, and IIA) as a suspending agent has been commercialized and recognized by pharmacopeias, as they do not affect the pourability or spreadibility of the suspension. Sarfaraz [17] reported the usage of magnabrite S (10 mg/ml) and magnabrite K (15 mg/ml) in bismuth sub-salicylate suspension in which smooth gel was obtained as a final product. The usage of MAS (veegum HV) as gelling agent was studied by Sarfaraz [17] and Vanderbilt report [21]. Vanderbilt report also suggested that the gelling property of veegum HV was affected by acids and improved by alkalies. An antacid suspension with veegum HV was prepared by Sarfaraz [17] using xanthan gum to modify viscosity. Schott [22] optimize the concentration of bentonite as suspending agent and concluded that the concentration between 0.5–5% w/v was suitable for formulations. Bismuth subnitrate suspension produces good floccula-

Many semisolid formulations use phyllosilicate as suspending agent due to their good adsorptive capacity which can be further improved by heating [23]. In many semisolid topical formulations, surface activated kaolin is added to enhance the stability and water miscibility of hydrophobic drug. Pharmaceutical preparation such as kaolin and morphine oral suspension BP, Toxiban suspension use kaolin as suspending anti-caking agent. The effect of crystallinity of kaolin on aqueous suspensions was studied by Ndlovu et al. Due to their dominant negative charge and ability to create permanent electrostatic repulsion justify kaolin use in suspension. The effect of non-ionic surfactant noigen RN10 (polyethylene alkyl phenyl ether) on kaolin wettability and stability was also studied. Clay can also help in stabilizing the suspension by having the effect on its rheological property since viscosity determines the rate of sedimentation according to stokes law. The different types and amount of clay are used to determine the final rheological property of the suspension. Dispersions showing dilant behavior contains 1:1 clay minerals and the pseudoplastic behavior is exhibited by 2:1 clay minerals. The commercialized MAS is a fibrous 2:1 clay containing blends of montmorellonite and seponite [6, 24, 25]. A combination of polyethylene glycol with hectorite improved the suspension stability [26, 27]. The modified hectorote such as quaternary C18 hectorite, Steralkonium hectorite is used in organic media to control

The use of clay along with polymers has shown beneficial effect on their rheological properties, which has been demonstrated in griseofulvin suspension with MAS and sodium alginate by Dechow et al. [29] in sulfamethoxazole/trimethoprim suspension. The synergistic effect of CMC on properties of MAS such as viscosity,

### *Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

*Clay Science and Technology*

As Granulating agent

As Emulsifying and wetting agent

As Suspending agent

As Drug delivery carrier

**Type of Excipient Clay minerals Drug used**

smectite, Magnesite

Kaolin, anhydrite, periclase

Kaolin, palygorskite, smectites, sylvite, halite

Kaolin, palygorskite, smectites, sylvite, halite

MMT-PLLA-PEG-PLLA

Modified MMT-Biopolymer Organomodified MMT-PVP/PCL MMT-Saponite-Chitosan Kaolinite-PVP-Sodium laural sulphate Natural HNT Natural Palygorskite Natural sepiolite HNT-Biopolymer HNT-Chitosan HNT-Alginate HNT-PEG HNT-PVA Sepiolite-Chitosan

Natural MMT Modified MMT Acid treated MMT MMT-Saponite Kaolinite pillared MMT Functionalized kaolinite Natural MMT-Biopolymer MMT-Chitosan MMT-Alginate MMT-Guar gum MMT-PLGA MMT-PLLA

Slim well tablet, Quantrim, Riclasip, Riboflavin

Granules of NaCl and kaolin in Tablets preparation

Diclofenac sodium, chlorhexidine, gallic acid,

5-amino salicylic acid, binase, tetracycline,

Ciprofloxacin, Ag-Nanoparticles of Tetracycline, gentamycin, theophylline, nitric oxide, acetyl

hard gelatine capsule

Hydrochlorothiazide

Sulfur ointments.

promethazine

Ibuprofen

Nicotine 5-flurouracil Chlorhexidine

Atorvastatin

salicylic acid, Ibuprofen Mesalazine, oxytetracycline Venlafaxine, olanzapine

Dexamethasone, atenolol 6-mercaptopurin Gemcitabine Naproxen, curcumin

amoxicillin, paclifaxel Ofloxacin, isoniazid Carvacrol, praziquantel Doxorubicin, aspirin, curcumin, Vancomycin, 5-flurouracil, hydrocortisone

Kaolin-Eudragit 30 in many tablets

Toxiban, morphine suspensions

As Diluent Kaolin, talc, sepiolite,

As Disintegrant Palygorskite, kaolin,

As Binder Gypsum, hydroxyapatite, kaolin

sepiolite

**102**

**Table 2.**

*2.1.1 In suspension*

sulfate, salicylate, hyoscyamine, hydrobromide, paracetamol, and chloroquine into periclase and brucite has been showed by Khalil et al. [15]. These interactions have been proven useful since they are used to retard drug release. So they aid in controlled

Excipients are required in the biphasic system in order to obtain proper wetting and to maintain stability of the formulation. In order to overcome the

drug release and improve the Tmax considerably.

**2.1 Clay in biphasic liquid formulation**

*Application of clay minerals as excipient.*

hydrophobicity of the drug and to aid in dispersion, clay minerals are added to the suspension as wetting agent. Sulfur ointment is prepared by blending kaolin with sulfur dispersed in oil phase [17]. The usage of bentonite as a wetting agent in foundation creams is also documented [18]. The clay also helps to maintain the stability by acting as suspending and anti-caking agent. They prevent sedimentation, changes in dispersion property, and flocculation. The criteria of selection of suitable suspending agent depend on compatibility, appearance, source, cost, and pH tolerance. The properties of the suspending agent including high viscosity at low shear rate, temperature, and storage tolerance, should not be affected by electrolyte or pH and be non-toxic. The formation of aggregates which in turn leads to the caking of solids would be the problem of suspension at the higher concentration. Reduction in the particle size or viscosity could not prevent caking. Caking can be prevented by flocculation and electrostatic stabilization [19, 20]. Kibbe showed that the increase in the stability of suspension using kaolin and talc as suspending and anti-caking agent. A suspension of pectin containing MAS dispersed in water along with kaolin under constant agitation at 70°C to which pectin was added, CMC was used to modify viscosity [17]. The usage of MAS and its four types (IA, IB, IC, and IIA) as a suspending agent has been commercialized and recognized by pharmacopeias, as they do not affect the pourability or spreadibility of the suspension. Sarfaraz [17] reported the usage of magnabrite S (10 mg/ml) and magnabrite K (15 mg/ml) in bismuth sub-salicylate suspension in which smooth gel was obtained as a final product. The usage of MAS (veegum HV) as gelling agent was studied by Sarfaraz [17] and Vanderbilt report [21]. Vanderbilt report also suggested that the gelling property of veegum HV was affected by acids and improved by alkalies. An antacid suspension with veegum HV was prepared by Sarfaraz [17] using xanthan gum to modify viscosity. Schott [22] optimize the concentration of bentonite as suspending agent and concluded that the concentration between 0.5–5% w/v was suitable for formulations. Bismuth subnitrate suspension produces good flocculation at 1.7% w/v of bentonite.

Many semisolid formulations use phyllosilicate as suspending agent due to their good adsorptive capacity which can be further improved by heating [23]. In many semisolid topical formulations, surface activated kaolin is added to enhance the stability and water miscibility of hydrophobic drug. Pharmaceutical preparation such as kaolin and morphine oral suspension BP, Toxiban suspension use kaolin as suspending anti-caking agent. The effect of crystallinity of kaolin on aqueous suspensions was studied by Ndlovu et al. Due to their dominant negative charge and ability to create permanent electrostatic repulsion justify kaolin use in suspension. The effect of non-ionic surfactant noigen RN10 (polyethylene alkyl phenyl ether) on kaolin wettability and stability was also studied. Clay can also help in stabilizing the suspension by having the effect on its rheological property since viscosity determines the rate of sedimentation according to stokes law. The different types and amount of clay are used to determine the final rheological property of the suspension. Dispersions showing dilant behavior contains 1:1 clay minerals and the pseudoplastic behavior is exhibited by 2:1 clay minerals. The commercialized MAS is a fibrous 2:1 clay containing blends of montmorellonite and seponite [6, 24, 25]. A combination of polyethylene glycol with hectorite improved the suspension stability [26, 27]. The modified hectorote such as quaternary C18 hectorite, Steralkonium hectorite is used in organic media to control viscosity [28].

The use of clay along with polymers has shown beneficial effect on their rheological properties, which has been demonstrated in griseofulvin suspension with MAS and sodium alginate by Dechow et al. [29] in sulfamethoxazole/trimethoprim suspension. The synergistic effect of CMC on properties of MAS such as viscosity,

electrolyte tolerance, smooth flow property has led to the development of Veegum PLUS [30]. A similar synergism has also found in xanthan gum [31, 32].

### *2.1.2 In emulsion*

Clay minerals are also added to pharmaceutical emulsion to prevent coalescence, creaming, phase inversion, breaking, and flocculation. This is due to their ability to wetted by the two liquid phases and be present as a barrier to prevent phase separation. Flocculation can be prevented by clay material due to their zeta potential. The stability of the emulsion is improved with increase in contact angle. They also used in the mechanical production of emulsion by acting as a surface acting agent which can bind in the interfacial layer but do not reduce the interfacial tension and interface. Due to its higher surface area, talc has been used as a emulgent in the cosmetic preparation [18]. The use of bentonite as emulsifying agent is familiar throughout the cosmetic industry. A nail enamel cream contains bentonite as an emulsifier was prepared by Carter [33]. He also proposed specific method of the cream preparation. Vanishing creams and skin protectants also use bentonite in a concentration of 2.5% w/v as emulgent [34]. In order to aid in easy application and adherent effect on the skin surface, clay minerals are added in corn and callus emulsion [34]. They are also added to hand creams as a thickening agent to retain better moisture control. The viscosity of the liquid eye liner formulation is maintained by addition of veegum [34]. Purified bentonite (Polargel NF) has been used as an emulsifying agent in cleansing lotion with HPMC and benzoyl peroxide. This has also been prepared as a cream by the addition of viscosity building agent (Carbomer) [17]. An anti-acne cream emulsion is prepared by using MAS [17]. MAS is also incorporated in cream emulsions for burns, methyl salicylate (analgesic effect), astringent zinc oxide, zirconium oxide and in zinc undecylenate lotions as a emulsifying agent [17]. Certain vitamins enriched skin creams also use MAS as emulsifier [30]. The synergic effect of xanthan gum along with MAS has been seen in zirconium oxide lotion [17]. Wenninger et al. [35] showed the usage of palygorskite as an emulgent (2–5% w/v). The presence of Na+ and K+ ions in halite and slyvite and their ability to control micelle size enumerate their use as emulsifying, thickening and anticaking agent [36]. The long-term stability of pickering emulsions (where dodecane is used as oil phase) is improved by addition of kaolin (15% w/v) without any other additives [37].

### **2.2 Use of clay as an excipient in solid dosage forms**

### *2.2.1 As diluent*

Pharmaceutical oral preparations contain excipients such as diluent, flavorant, binder, disintegrant, pelletizing agent, granulating agent, sweetening agents, film coating agent, lubricant, and desiccants. Each excipient has its own influence on the formulation without interfering with active drug. It enhances the organoleptic and physiochemical property of the formulation. Diluents are selected based on the water solubility and bioavailability of active drug. Formulations with less water soluble drugs are incorporated with water soluble diluents and vice versa. Kaolin exhibit non-hygroscopic nature and low moisture content which determines its effectiveness as a diluent, as high moisture content may affect compressibility, physical and chemical stability of the formulation. Physiochemical parameters of kaolin have a direct impact over compressibility of the formulation [38]. The usage of kaolin as excipient for their adsorbent capacity has to be

**105**

*Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

kaolin than other additives [56, 57].

added as binders to increase the stomach pH [60].

*2.2.2 As binders*

properly maintained since high adsorbent capacity can lead to less bioavailability of the drug [38–40]. Diluents are mainly added to the formulation to bulk up the volume and to facilitate easy compression. Diluents account for the 90% in low dose formulation. Product such as slim-well and quantrim use kaolin as bulking agent whereas mecysteine hydrochloride (Gastro resistant tablet) has heavy grade kaolin. Riclasip and co-amoxyclav DST grunenthal uses kaolin as adjuvant [41]. The use of kaolin with metronidazole (antibiotic and antifungal drug, Riazole) reduces its bioavailability, release characteristic and diffusion of drug inside the body [42]. The absorption of D, L-phenylalanine (analgesic and anti-depressant) onto the slurry of colloidal kaolin was showed by Bonner and Flores [43] through in vitro gross adsorption chromatographic study. Kaolin also affect the bioavailability of drugs like phenytoin (anti-seizure drug), promethazine-HCl (sedative and antiallergic drug), chloroquine (anti-malarial), propranolol (vasodilator), quinidine sulphate (cardiac antiarrhythmic drug), phenothiazines (trifluoperazine, fluphenazine, perphenazine, and thioridazine), guanethidine and hydralazine (antihypertensive drugs), procainamide and verapamil (antiarrhythmic drugs) with antidiarrheal Kaopectate® drug [44–49]. It has been reported that Langmuir isotherm was followed in drug absorption by kaopectate which extent the bioavailability but the rate of drug availability is retarded. The double layered adsorption pattern of mebeverine hydrochloride (antispasmodic drug) with kaolin and added electrolytes again follows Langmuir isotherm was studied by Al Gohary. These types of interactions of kaolin can be prevented by increasing the ionic strength of the drug solution and with the presence of –NH2, –O–, and benzene ring, as chelating ligands led to the interaction. The presence of di-aromatic ring in naproxen (anti-inflammatory drug) and siloxane surface of kaolin are responsible for their interaction [50]. On other hand, the absorption of ampicillin and warfarin (anticoagulant) with antidiarrheal kaolin-pectin is shown to be unaffected by kaolin [51, 52], which was again conformed by Khalil et al. [53]. In fact, the use of kaolin as diluent in water soluble cationic riboflavin (vitamin B2) has improved the release rate of drug from hard gelatin capsule than any other diluents used. The rate of drug release is pH dependent [54]. The sustained release formulation of pyridoxine hydrochloride (vitamin B6) was prepared by using kaolin as diluent [55]. Vitamin drugs degrade easily in the presence of high moisture content since kaolin exhibit low moisture content the formulation containing vitamin B1 (thiamine) and Vitamin C (ascorbic acid) is more stable on addition of

Binders help to maintain the physical integrity of the solid dosage form owing to their mechanical strength. They also play a vital role in granulation, tableting, encapsulation by acting as a homogeneous dispersed matrix for adhesion of all material in the formulation. On this context, the mixture of kaolin-Eudragit (8% w/w) has been one of the good binders for tableting process. Eudragit is a poly ester based resin which exhibit hydrophilicity and does not get affected by varying pH and also the presence of kaolin help to obtain a uniform polymeric dispersion by differentiating water insoluble and hydrophilic particle within the system. Irrespective of their physiochemical properties, hydrophilic drugs are also blended with low water soluble drug in the kaolin-Eudragit formulation due to their larger permeability. Based on kaolin concentration they can also be used as film coating agent [58, 59]. Minerals like periclase, calcite, and magnesite are

### *Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

*Clay Science and Technology*

(2–5% w/v). The presence of Na+

**2.2 Use of clay as an excipient in solid dosage forms**

additives [37].

*2.2.1 As diluent*

*2.1.2 In emulsion*

electrolyte tolerance, smooth flow property has led to the development of Veegum

Clay minerals are also added to pharmaceutical emulsion to prevent coalescence, creaming, phase inversion, breaking, and flocculation. This is due to their ability to wetted by the two liquid phases and be present as a barrier to prevent phase separation. Flocculation can be prevented by clay material due to their zeta potential. The stability of the emulsion is improved with increase in contact angle. They also used in the mechanical production of emulsion by acting as a surface acting agent which can bind in the interfacial layer but do not reduce the interfacial tension and interface. Due to its higher surface area, talc has been used as a emulgent in the cosmetic preparation [18]. The use of bentonite as emulsifying agent is familiar throughout the cosmetic industry. A nail enamel cream contains bentonite as an emulsifier was prepared by Carter [33]. He also proposed specific method of the cream preparation. Vanishing creams and skin protectants also use bentonite in a concentration of 2.5% w/v as emulgent [34]. In order to aid in easy application and adherent effect on the skin surface, clay minerals are added in corn and callus emulsion [34]. They are also added to hand creams as a thickening agent to retain better moisture control. The viscosity of the liquid eye liner formulation is maintained by addition of veegum [34]. Purified bentonite (Polargel NF) has been used as an emulsifying agent in cleansing lotion with HPMC and benzoyl peroxide. This has also been prepared as a cream by the addition of viscosity building agent (Carbomer) [17]. An anti-acne cream emulsion is prepared by using MAS [17]. MAS is also incorporated in cream emulsions for burns, methyl salicylate (analgesic effect), astringent zinc oxide, zirconium oxide and in zinc undecylenate lotions as a emulsifying agent [17]. Certain vitamins enriched skin creams also use MAS as emulsifier [30]. The synergic effect of xanthan gum along with MAS has been seen in zirconium oxide lotion [17]. Wenninger et al. [35] showed the usage of palygorskite as an emulgent

PLUS [30]. A similar synergism has also found in xanthan gum [31, 32].

and K+

to control micelle size enumerate their use as emulsifying, thickening and anticaking agent [36]. The long-term stability of pickering emulsions (where dodecane is used as oil phase) is improved by addition of kaolin (15% w/v) without any other

Pharmaceutical oral preparations contain excipients such as diluent, flavorant, binder, disintegrant, pelletizing agent, granulating agent, sweetening agents, film coating agent, lubricant, and desiccants. Each excipient has its own influence on the formulation without interfering with active drug. It enhances the organoleptic and physiochemical property of the formulation. Diluents are selected based on the water solubility and bioavailability of active drug. Formulations with less water soluble drugs are incorporated with water soluble diluents and vice versa. Kaolin exhibit non-hygroscopic nature and low moisture content which determines its effectiveness as a diluent, as high moisture content may affect compressibility, physical and chemical stability of the formulation. Physiochemical parameters of kaolin have a direct impact over compressibility of the formulation [38]. The usage of kaolin as excipient for their adsorbent capacity has to be

ions in halite and slyvite and their ability

**104**

properly maintained since high adsorbent capacity can lead to less bioavailability of the drug [38–40]. Diluents are mainly added to the formulation to bulk up the volume and to facilitate easy compression. Diluents account for the 90% in low dose formulation. Product such as slim-well and quantrim use kaolin as bulking agent whereas mecysteine hydrochloride (Gastro resistant tablet) has heavy grade kaolin. Riclasip and co-amoxyclav DST grunenthal uses kaolin as adjuvant [41]. The use of kaolin with metronidazole (antibiotic and antifungal drug, Riazole) reduces its bioavailability, release characteristic and diffusion of drug inside the body [42]. The absorption of D, L-phenylalanine (analgesic and anti-depressant) onto the slurry of colloidal kaolin was showed by Bonner and Flores [43] through in vitro gross adsorption chromatographic study. Kaolin also affect the bioavailability of drugs like phenytoin (anti-seizure drug), promethazine-HCl (sedative and antiallergic drug), chloroquine (anti-malarial), propranolol (vasodilator), quinidine sulphate (cardiac antiarrhythmic drug), phenothiazines (trifluoperazine, fluphenazine, perphenazine, and thioridazine), guanethidine and hydralazine (antihypertensive drugs), procainamide and verapamil (antiarrhythmic drugs) with antidiarrheal Kaopectate® drug [44–49]. It has been reported that Langmuir isotherm was followed in drug absorption by kaopectate which extent the bioavailability but the rate of drug availability is retarded. The double layered adsorption pattern of mebeverine hydrochloride (antispasmodic drug) with kaolin and added electrolytes again follows Langmuir isotherm was studied by Al Gohary. These types of interactions of kaolin can be prevented by increasing the ionic strength of the drug solution and with the presence of –NH2, –O–, and benzene ring, as chelating ligands led to the interaction. The presence of di-aromatic ring in naproxen (anti-inflammatory drug) and siloxane surface of kaolin are responsible for their interaction [50]. On other hand, the absorption of ampicillin and warfarin (anticoagulant) with antidiarrheal kaolin-pectin is shown to be unaffected by kaolin [51, 52], which was again conformed by Khalil et al. [53]. In fact, the use of kaolin as diluent in water soluble cationic riboflavin (vitamin B2) has improved the release rate of drug from hard gelatin capsule than any other diluents used. The rate of drug release is pH dependent [54]. The sustained release formulation of pyridoxine hydrochloride (vitamin B6) was prepared by using kaolin as diluent [55]. Vitamin drugs degrade easily in the presence of high moisture content since kaolin exhibit low moisture content the formulation containing vitamin B1 (thiamine) and Vitamin C (ascorbic acid) is more stable on addition of kaolin than other additives [56, 57].

### *2.2.2 As binders*

Binders help to maintain the physical integrity of the solid dosage form owing to their mechanical strength. They also play a vital role in granulation, tableting, encapsulation by acting as a homogeneous dispersed matrix for adhesion of all material in the formulation. On this context, the mixture of kaolin-Eudragit (8% w/w) has been one of the good binders for tableting process. Eudragit is a poly ester based resin which exhibit hydrophilicity and does not get affected by varying pH and also the presence of kaolin help to obtain a uniform polymeric dispersion by differentiating water insoluble and hydrophilic particle within the system. Irrespective of their physiochemical properties, hydrophilic drugs are also blended with low water soluble drug in the kaolin-Eudragit formulation due to their larger permeability. Based on kaolin concentration they can also be used as film coating agent [58, 59]. Minerals like periclase, calcite, and magnesite are added as binders to increase the stomach pH [60].

### *2.2.3 As disintegrant*

The release of drug from the formulation once it reaches inside the body mainly depends on the nature of the disintegrant used during formulation. Disintegrant facilitate breakdown of solid dosage form into smaller particulates. Poor solubility, poor gel forming capacity, good hydration capacity, good molding, flow property, and should not form complex are the required criteria for disintegrants. Both swelling property and ability to decompose at acidic environment of smectite made its use as a disintegrating agent. The presence of negative charge and ability to produce permanent negative surface charges helps kaolin as a disintegrant [61, 62]. A mixture of kaolin with surfactant and cellulose when added to formulation which already has starch as a disintegrant increased its shelf life over a long period of time [63]. Later, the use of kaolin as a positive effect than starch as a disintegrant has been proved [64].

### *2.2.4 As pelletizing agent*

Kaolin proved its efficiency over bentonite by forming pellets which show faster disintegration while the pellets formed by bentonite was only erodible not disintegrable [65]. Kaolin along with biopolymer increase the drug dissolution rate of hydrochlorothiazide by forming pellets that rapidly disintegrated into the dissolution medium [66]. The primary aim of pelletizing agent is to form microspheres of uniform size which can be compressed into tablets or filled into capsules that rapidly disintegrates inside gastrointestinal drug where each pellet act as sustain formulation [67, 68]. Kaolin as a pelletizing agent in comparison with bentonite, talc, veegum and bentonite produce pellets with maximum yield, desirable size and smooth pellets on addition of SLS (5%) over the others [69]. The beneficial effect of crospovidone (5% w/w) and kaolin (25% w/w) with lactose as pelletizing agent for enhancing roundness and sphericity of pellets was demonstrated by Kristensen et al. [65]. The drug dissolution rate of riboflavin was higher with kaolin than microcrystalline cellulose and lactose [66]. Desirable size range and sphericity can be obtained by incorporating high kaolin content. Aerosil 200 (5%) along with kaolin (45%) has huge positive impact on sphericity of pellets [70]. The granulating agent is added to the formulation to improve flow property, density, appearance and uniform drug content, they also aid in compressibility of oral formulation. Wet and dry granulations are most commonly used method of granule preparation. Wet granulation involves wetting, nucleation, coalescence, breakage, and attrition process whereas dry granulation involves direct compression or slugging [71, 72]. Granules of desirable strength, size, cohesion, and uniformity can be produced by mixture of kaolin and sodium chloride (10% w/w) in wet granulation process. The comparative study of kaolin with polyethylene glycol and polyvinyl alcohol as a binder in calcium chloride showed kaolin PVA mixture gave larger yield and size than PGA kaolin mixture [73].

### *2.2.5 Aid in solubility, dissolution, and lubrication*

Kaolin also helps to convert drugs form their crystalline to amorphous state to improve their solubility, dissolution rate, and bioavailability [74–76]. Kaolin was added to ibuprofen in order to convert it to amorphous salt from its crystalline form to facilitate higher dissolution and bioavailability in comparison with standard. Halite can be used to control osmolarity of the solution due to their high solubility in water [77]. Amorphization is inversely proportional to the kaolin concentration [74]. Clays are also used as desiccants due to their hygroscopic nature. Talc is used as lubricant and

**107**

**3.1 Antacid**

*Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

*2.2.7 Enhancer of organoleptic properties*

rutile is used on sunscreen lotion as opacifier.

acid or by decomposition of minerals by absorbing H+

**3. Use of clay as an active ingredient**

gibbsite is slow acting antacid [82].

**3.2 Wound dressing agent**

*2.2.6 As coating agent*

to prevent adhesion of powder to the compression pistons due to their soft and unctuous nature [78]. They are also used as flavorant to mask the taste of the formulation.

The use of film coating additive enhance the organoleptic characters of solid dosage form, helps in maintaining stability and control drug release profile [79, 80]. The decrease in the rate of drug release of diphenhydramine chloride, theophylline, and pseudoephedrine hydrochloride pellets coated with Eudragit on addition of kaolin (3:1 of resin) was studied by Ghebre-Sellassie et al. [58]. Kaolin is also added to the film coating of hypericon and kollicoat IR. Kaolin incorporated on the outer shell of triple pressed dyphylline coated tablets showed control release [81].

The organoleptic property of a drug can be modified on addition of excipients like pigments and opacifiers into tablets, capsules, syrups, and topical creams. These are necessary to avoid confusion while administering multiple medications and for easy identification of different dosages and help to protect the drugs from photo-oxidative damage. Clay minerals (calcite, rutile, hematite, and magnesite) possess a wide range of color from red, green, black, yellow, and white. Coloring E171 is most used pigment which is a synthetic analogue of white zincite. Synthetic

Clay minerals also has its application as active ingredient in pharmaceutical preparation due to their ability to act as antacids, antianemics, mineral supplements, gastric protectors, laxative, antidiarrhoeaics, antibiotics, antiviral agents, wound dressing agent, detoxifier, antitumor agent, anti-inflammatory, and tropical analgesic.

Acidity is caused by excess secretion of HCl in the stomach due to various conditions. Clay minerals overcome acidity either by neutralizing hydrochloric

onto their surface. Their usage also can lead to certain side effects such as renal silica calculi, constipation in case of over accumulation of Ca2+ since they form insoluble hydrate phosphate and Mg2+ ion produces laxative effect but these effects can be avoided by using different mineral compositions. This combination has also an advantage of sustaining the drug release for example the co-administration of gibbsite with brusite prolonged its antacid action since brusite is fast acting and

restoring the stomach pH to 7 from 1.5 to 2.5. An effective antacid must increase the pH by three to four units and decrease the free acidity, which is seen in clay minerals like calcite, magnesite, periclase, brucite, and hydrotalcite. Whereas palygorskite, sepioite, montmorillonite, and saponite neutralize acidity by absorbing H<sup>+</sup>

Wounds characterized by skin abrasion and vascular damage can lead to microbial invasion, toxicity, and even hemorrhagic shock due to uncontrolled bleeding.

ion on to their surface. Thus,

ion

to prevent adhesion of powder to the compression pistons due to their soft and unctuous nature [78]. They are also used as flavorant to mask the taste of the formulation.

### *2.2.6 As coating agent*

*Clay Science and Technology*

The release of drug from the formulation once it reaches inside the body mainly depends on the nature of the disintegrant used during formulation. Disintegrant facilitate breakdown of solid dosage form into smaller particulates. Poor solubility, poor gel forming capacity, good hydration capacity, good molding, flow property, and should not form complex are the required criteria for disintegrants. Both swelling property and ability to decompose at acidic environment of smectite made its use as a disintegrating agent. The presence of negative charge and ability to produce permanent negative surface charges helps kaolin as a disintegrant [61, 62]. A mixture of kaolin with surfactant and cellulose when added to formulation which already has starch as a disintegrant increased its shelf life over a long period of time [63]. Later, the use of kaolin as a positive effect than starch as a disintegrant has

Kaolin proved its efficiency over bentonite by forming pellets which show faster disintegration while the pellets formed by bentonite was only erodible not disintegrable [65]. Kaolin along with biopolymer increase the drug dissolution rate of hydrochlorothiazide by forming pellets that rapidly disintegrated into the dissolution medium [66]. The primary aim of pelletizing agent is to form microspheres of uniform size which can be compressed into tablets or filled into capsules that rapidly disintegrates inside gastrointestinal drug where each pellet act as sustain formulation [67, 68]. Kaolin as a pelletizing agent in comparison with bentonite, talc, veegum and bentonite produce pellets with maximum yield, desirable size and smooth pellets on addition of SLS (5%) over the others [69]. The beneficial effect of crospovidone (5% w/w) and kaolin (25% w/w) with lactose as pelletizing agent for enhancing roundness and sphericity of pellets was demonstrated by Kristensen et al. [65]. The drug dissolution rate of riboflavin was higher with kaolin than microcrystalline cellulose and lactose [66]. Desirable size range and sphericity can be obtained by incorporating high kaolin content. Aerosil 200 (5%) along with kaolin (45%) has huge positive impact on sphericity of pellets [70]. The granulating agent is added to the formulation to improve flow property, density, appearance and uniform drug content, they also aid in compressibility of oral formulation. Wet and dry granulations are most commonly used method of granule preparation. Wet granulation involves wetting, nucleation, coalescence, breakage, and attrition process whereas dry granulation involves direct compression or slugging [71, 72]. Granules of desirable strength, size, cohesion, and uniformity can be produced by mixture of kaolin and sodium chloride (10% w/w) in wet granulation process. The comparative study of kaolin with polyethylene glycol and polyvinyl alcohol as a binder in calcium chloride showed kaolin PVA mixture gave larger yield and size

*2.2.3 As disintegrant*

been proved [64].

*2.2.4 As pelletizing agent*

than PGA kaolin mixture [73].

*2.2.5 Aid in solubility, dissolution, and lubrication*

Kaolin also helps to convert drugs form their crystalline to amorphous state to improve their solubility, dissolution rate, and bioavailability [74–76]. Kaolin was added to ibuprofen in order to convert it to amorphous salt from its crystalline form to facilitate higher dissolution and bioavailability in comparison with standard. Halite can be used to control osmolarity of the solution due to their high solubility in water [77]. Amorphization is inversely proportional to the kaolin concentration [74]. Clays are also used as desiccants due to their hygroscopic nature. Talc is used as lubricant and

**106**

The use of film coating additive enhance the organoleptic characters of solid dosage form, helps in maintaining stability and control drug release profile [79, 80]. The decrease in the rate of drug release of diphenhydramine chloride, theophylline, and pseudoephedrine hydrochloride pellets coated with Eudragit on addition of kaolin (3:1 of resin) was studied by Ghebre-Sellassie et al. [58]. Kaolin is also added to the film coating of hypericon and kollicoat IR. Kaolin incorporated on the outer shell of triple pressed dyphylline coated tablets showed control release [81].

### *2.2.7 Enhancer of organoleptic properties*

The organoleptic property of a drug can be modified on addition of excipients like pigments and opacifiers into tablets, capsules, syrups, and topical creams. These are necessary to avoid confusion while administering multiple medications and for easy identification of different dosages and help to protect the drugs from photo-oxidative damage. Clay minerals (calcite, rutile, hematite, and magnesite) possess a wide range of color from red, green, black, yellow, and white. Coloring E171 is most used pigment which is a synthetic analogue of white zincite. Synthetic rutile is used on sunscreen lotion as opacifier.

### **3. Use of clay as an active ingredient**

Clay minerals also has its application as active ingredient in pharmaceutical preparation due to their ability to act as antacids, antianemics, mineral supplements, gastric protectors, laxative, antidiarrhoeaics, antibiotics, antiviral agents, wound dressing agent, detoxifier, antitumor agent, anti-inflammatory, and tropical analgesic.

### **3.1 Antacid**

Acidity is caused by excess secretion of HCl in the stomach due to various conditions. Clay minerals overcome acidity either by neutralizing hydrochloric acid or by decomposition of minerals by absorbing H+ ion on to their surface. Thus, restoring the stomach pH to 7 from 1.5 to 2.5. An effective antacid must increase the pH by three to four units and decrease the free acidity, which is seen in clay minerals like calcite, magnesite, periclase, brucite, and hydrotalcite. Whereas palygorskite, sepioite, montmorillonite, and saponite neutralize acidity by absorbing H<sup>+</sup> ion onto their surface. Their usage also can lead to certain side effects such as renal silica calculi, constipation in case of over accumulation of Ca2+ since they form insoluble hydrate phosphate and Mg2+ ion produces laxative effect but these effects can be avoided by using different mineral compositions. This combination has also an advantage of sustaining the drug release for example the co-administration of gibbsite with brusite prolonged its antacid action since brusite is fast acting and gibbsite is slow acting antacid [82].

### **3.2 Wound dressing agent**

Wounds characterized by skin abrasion and vascular damage can lead to microbial invasion, toxicity, and even hemorrhagic shock due to uncontrolled bleeding.

This is countered by our body homeostatic response through coagulation of blood which prevents bleeding. Hemostasis follows sequential steps like: (1) thrombin formation is initiated, (2) activation and platelet aggregation (amplification), and (3) fibrin formation to stabilize the platelet clot (propagation). Hemostatic agents provide a physical mesh-like layer which aid in amplification and propagation steps of hemostasis thus leading to platelet aggregation and coagulation. The negative surface charge of kaolin at blood and plasma pH has a drastic effect on its blood clotting potential. The activation of blood coagulation factor XII to its active is done by kaolin on contact with blood and plasma. The active form of factor XII in turn activates factor XI and pre-kallikrein which helps in preventing bleeding. Therefore, many wound dressing products contain kaolin as topical hemostatic agents (Quickclot combat GauzeXL, Quickclotinterventional™) [83–87].

### **3.3 Peptic ulcer**

Peptic ulcer is characterized by thinning of mucosal layer of the stomach due to the mucolytic activity of stomach enzymes, in order to reduce gastric irritation and provide a barrier for mucosal layer several clay minerals are used for their high sorption capacity and non-toxicity. These clay minerals absorb all the gases, toxins, bacteria and even viruses and reduce gastric secretions. They also act as protectants decreasing the glycoprotein degradation in the stomach. But their nonspecific action has led to their minimal usage. Even though smectites prevent the pepsin damaging activity over the mucosal layer, their very less time of action and tendency to get degraded in the acidic medium has been a disadvantage but kaolin can be stable and show very low dissolution even at very less pH. They are taken as tablets, suspensions, or powders orally. They dissolve easily in the acidic medium aiding in their easy elimination and absorption [82, 88–90]. Kaolin due to their higher sorptive capacity delay gastric emptying and intestinal transit by enhancing triacylglycerol hydrolysis and promoting the intestinal uptake of non-esterified fatty acid and glucose [91].

### **3.4 Anti-diarrheal agent and anti-emetics**

Kaolin has been used as an API in formulations for gastrointestinal like ASDA stomach upset tablets, Entroclam, or Boots kaolin [92, 93]. Diarrhea is caused by various factors like allergy, bacterial infection, intoxication, and low efficiency of intestinal sorption. It is characterized by increase in fluidity and frequency of evacuation. Anti-diarrhoeaics agents must have very good absorption capacity of excess water as well as gases in the digestive tracts. Activated clay minerals like kaolinite, palygorskite, sepiolite, and montmorillonite can be used against diarrhea for their high sorption capacity. They also prevent diarrhea by forming in soluble salts through release of Ca2+ (calcite) and Al3+ (gibbsite) ions [94–97]. Pharmaceutical products such as kaolin/pectin (Kaopectate®) and Kaomix® suspensions, kaolin Antacil®, Sainsbury's Diarrhea relief® and Treda® tablets contain kaolin as active ingredient against diarrhea due to hydrophilicity, surface area, microporosity, water osmotic and retention property as well as its antibacterial and antiviral effect (e.g., Norwalk and rotavirus, salmonella, Shigella and *Escherichia coli* bacteria) [98–101]. Minerals rich in Mg2+ or Na+ ion (mirabilite, epsomite, brucite, periclase, and magnesite) can act as laxative by increasing the osmatic pressure of the intestinal content which induces water level increase in the intestine and finally producing liquid feces. They are given as solutions, granules, and suspensions, and these ions are mostly excreted through fecal matter and a small amount through kidney or bile duct. Halite and sylvite are administered as saline through oral or parental

**109**

*Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

**3.5 In anemia and inflammation**

them through vomit.

ions such as Ca2+, Na+

**3.6 Anti-bacterial**

route for the purpose of electrolyte replenishment (Na<sup>+</sup>

, Ca2+, Fe2+, K+

since it can have an effect over its therapeutic action [103–108].

through urine. Minerals rich in Cu2+ and Zn2+ (chalcocite, goslarite, and zincosite) can irritate gastric mucosa and trigger vomiting so they are used as direct emetic agents. When they reach intestine from stomach, they cause diarrhea. They are given orally as solutions. It can also be used to treat metal poisoning by removing

The use of clay minerals extents till its usage in disease like anemia. Anemia is caused due to less production red blood cells which may be due to less availability of Fe2+. This can be treated with melanterite which is rich in Fe2+ ion and readily soluble in water. They are given as oral solution; these ions on reaching blood plasma convert into ferric ion by binding with a transferrin and globulin β. The excession is stored in liver, spleen, and bone marrow. Some are excreted through urine, gall bladder, and bile duct. Orally administered halite, epsomite, brucite, periclase, calcite, hydroxyapatite, magnesite, sylvite, melanterite as tablets provide

, PO4

to our body [82]. Inflammatory response in our body is triggered to produce white blood cells and their mobility towards the injured site from infection through antigens or other harmful micro-organisms. Swelling, redness, pain, and heat are the main symptoms of inflammatory response. Lopez-Galindo and Viseras [102] presented the use of kaolinite poultices as anti-inflammatory drug, since they can absorb the excess fluid content near the infected tissue, which reduces pain and congestion considerably. They also aid in skin cooling by acting as a heat retention agent. Proper care of temperature must be taken while administering these dosages

Minerals like sulfur, goslarite, borax, zincosite, chalcanthite, zincite, and alum are highly corrosive and toxic to pathogens in higher concentration hence they can be used as an antiseptic or disinfectant. They are also used as an astringent (chalcanthite), bacteriostatic agent (borax), fungicide, hemostatic agent (alum), and for skin damage. The bactericidal activity of clay extents to many drug resistant bacteria like *Pseudomonas aeruginosa, E. coli, and Staphylococcus aureus* due to their physical and chemical properties that help them to envelope bacterial cells and interrupting their nutrient uptake, this is due to their high surface attraction towards the bacterial cell wall. Ions present in clay minerals also play an important role in their bactericidal property. Divalent cations like Cu2+ and Fe2+ are easily transferred and oxidized inside the bacterial cell to produce intercellular hydroxyl radicle which are lethal to them. The tri- or tetravalent cations show their activity inhibiting the influx or efflux pumps. Many modified clays have been reported to have good bactericidal activity, for example the photocatalytic activity of zinc oxide and Ti make TiO2 (ZnO)/kaolinite make the effective against *Enterococcus faecalis, E. coli, and Pseudomonas aeruginosa.* Moreover, *Pseudomonas aeruginosa* is also susceptible to kaolin modified with CTAB and Cu. Oral pathogens like *E. coli, Bacillus subtilis, and klebsiella pneumonia* are effectively killed by kaolin/iron-porphyrin hybrid. Nano-composite of silver-kaolinite also demonstrated to have antibacterial property [109]. They use clay as an adsorbate to remove pathogenic viruses and certain phages are under investigation since the twentieth century. First it is thought that viruses by electrostatic interaction are adsorbed onto the clay surface due to their valency associated cations and cation exchange capacity but later studies showed

and K<sup>+</sup>

<sup>3</sup>−, and Mg2+ which are very much essential

). They are excreted

*Clay Science and Technology*

**3.3 Peptic ulcer**

fatty acid and glucose [91].

**3.4 Anti-diarrheal agent and anti-emetics**

[98–101]. Minerals rich in Mg2+ or Na+

This is countered by our body homeostatic response through coagulation of blood which prevents bleeding. Hemostasis follows sequential steps like: (1) thrombin formation is initiated, (2) activation and platelet aggregation (amplification), and (3) fibrin formation to stabilize the platelet clot (propagation). Hemostatic agents provide a physical mesh-like layer which aid in amplification and propagation steps of hemostasis thus leading to platelet aggregation and coagulation. The negative surface charge of kaolin at blood and plasma pH has a drastic effect on its blood clotting potential. The activation of blood coagulation factor XII to its active is done by kaolin on contact with blood and plasma. The active form of factor XII in turn activates factor XI and pre-kallikrein which helps in preventing bleeding. Therefore, many wound dressing products contain kaolin as topical hemostatic agents (Quickclot combat GauzeXL, Quickclotinterventional™) [83–87].

Peptic ulcer is characterized by thinning of mucosal layer of the stomach due to the mucolytic activity of stomach enzymes, in order to reduce gastric irritation and provide a barrier for mucosal layer several clay minerals are used for their high sorption capacity and non-toxicity. These clay minerals absorb all the gases, toxins, bacteria and even viruses and reduce gastric secretions. They also act as protectants decreasing the glycoprotein degradation in the stomach. But their nonspecific action has led to their minimal usage. Even though smectites prevent the pepsin damaging activity over the mucosal layer, their very less time of action and tendency to get degraded in the acidic medium has been a disadvantage but kaolin can be stable and show very low dissolution even at very less pH. They are taken as tablets, suspensions, or powders orally. They dissolve easily in the acidic medium aiding in their easy elimination and absorption [82, 88–90]. Kaolin due to their higher sorptive capacity delay gastric emptying and intestinal transit by enhancing triacylglycerol hydrolysis and promoting the intestinal uptake of non-esterified

Kaolin has been used as an API in formulations for gastrointestinal like ASDA stomach upset tablets, Entroclam, or Boots kaolin [92, 93]. Diarrhea is caused by various factors like allergy, bacterial infection, intoxication, and low efficiency of intestinal sorption. It is characterized by increase in fluidity and frequency of evacuation. Anti-diarrhoeaics agents must have very good absorption capacity of excess water as well as gases in the digestive tracts. Activated clay minerals like kaolinite, palygorskite, sepiolite, and montmorillonite can be used against diarrhea for their high sorption capacity. They also prevent diarrhea by forming in soluble salts through release of Ca2+ (calcite) and Al3+ (gibbsite) ions [94–97]. Pharmaceutical products such as kaolin/pectin (Kaopectate®) and Kaomix® suspensions, kaolin Antacil®, Sainsbury's Diarrhea relief® and Treda® tablets contain kaolin as active ingredient against diarrhea due to hydrophilicity, surface area, microporosity, water osmotic and retention property as well as its antibacterial and antiviral effect (e.g., Norwalk and rotavirus, salmonella, Shigella and *Escherichia coli* bacteria)

and magnesite) can act as laxative by increasing the osmatic pressure of the intestinal content which induces water level increase in the intestine and finally producing liquid feces. They are given as solutions, granules, and suspensions, and these ions are mostly excreted through fecal matter and a small amount through kidney or bile duct. Halite and sylvite are administered as saline through oral or parental

ion (mirabilite, epsomite, brucite, periclase,

**108**

route for the purpose of electrolyte replenishment (Na<sup>+</sup> and K<sup>+</sup> ). They are excreted through urine. Minerals rich in Cu2+ and Zn2+ (chalcocite, goslarite, and zincosite) can irritate gastric mucosa and trigger vomiting so they are used as direct emetic agents. When they reach intestine from stomach, they cause diarrhea. They are given orally as solutions. It can also be used to treat metal poisoning by removing them through vomit.

### **3.5 In anemia and inflammation**

The use of clay minerals extents till its usage in disease like anemia. Anemia is caused due to less production red blood cells which may be due to less availability of Fe2+. This can be treated with melanterite which is rich in Fe2+ ion and readily soluble in water. They are given as oral solution; these ions on reaching blood plasma convert into ferric ion by binding with a transferrin and globulin β. The excession is stored in liver, spleen, and bone marrow. Some are excreted through urine, gall bladder, and bile duct. Orally administered halite, epsomite, brucite, periclase, calcite, hydroxyapatite, magnesite, sylvite, melanterite as tablets provide ions such as Ca2+, Na+ , Ca2+, Fe2+, K+ , PO4 <sup>3</sup>−, and Mg2+ which are very much essential to our body [82]. Inflammatory response in our body is triggered to produce white blood cells and their mobility towards the injured site from infection through antigens or other harmful micro-organisms. Swelling, redness, pain, and heat are the main symptoms of inflammatory response. Lopez-Galindo and Viseras [102] presented the use of kaolinite poultices as anti-inflammatory drug, since they can absorb the excess fluid content near the infected tissue, which reduces pain and congestion considerably. They also aid in skin cooling by acting as a heat retention agent. Proper care of temperature must be taken while administering these dosages since it can have an effect over its therapeutic action [103–108].

### **3.6 Anti-bacterial**

Minerals like sulfur, goslarite, borax, zincosite, chalcanthite, zincite, and alum are highly corrosive and toxic to pathogens in higher concentration hence they can be used as an antiseptic or disinfectant. They are also used as an astringent (chalcanthite), bacteriostatic agent (borax), fungicide, hemostatic agent (alum), and for skin damage. The bactericidal activity of clay extents to many drug resistant bacteria like *Pseudomonas aeruginosa, E. coli, and Staphylococcus aureus* due to their physical and chemical properties that help them to envelope bacterial cells and interrupting their nutrient uptake, this is due to their high surface attraction towards the bacterial cell wall. Ions present in clay minerals also play an important role in their bactericidal property. Divalent cations like Cu2+ and Fe2+ are easily transferred and oxidized inside the bacterial cell to produce intercellular hydroxyl radicle which are lethal to them. The tri- or tetravalent cations show their activity inhibiting the influx or efflux pumps. Many modified clays have been reported to have good bactericidal activity, for example the photocatalytic activity of zinc oxide and Ti make TiO2 (ZnO)/kaolinite make the effective against *Enterococcus faecalis, E. coli, and Pseudomonas aeruginosa.* Moreover, *Pseudomonas aeruginosa* is also susceptible to kaolin modified with CTAB and Cu. Oral pathogens like *E. coli, Bacillus subtilis, and klebsiella pneumonia* are effectively killed by kaolin/iron-porphyrin hybrid. Nano-composite of silver-kaolinite also demonstrated to have antibacterial property [109]. They use clay as an adsorbate to remove pathogenic viruses and certain phages are under investigation since the twentieth century. First it is thought that viruses by electrostatic interaction are adsorbed onto the clay surface due to their valency associated cations and cation exchange capacity but later studies showed

that amino acid and carboxylic residue present on the outer shell viral protein coat is responsible for the net charge and their adsorption into clay minerals depends on pH, ionic strength, and isoelectric points of the clay and virus. Further studies show that hydrophobic interactions of crystallized kaolin show greater affinity for certain bacteriophages. In vitro studies of kaolin against hepatitis C virus, human enteric pathogenic adenoviruses (hAdVs) and adenovirus (HAdV-5) proved kaolin to be an effective material that could be used against certain viral infections [110]. Many substances like heavy metals, toxins, mycotoxins, and overdosed drug compounds can be removed from the gastrointestinal tract by administering kaolin as a detoxifying agent.

### **3.7 Miscellaneous**

Kaolin is found to influence superoxide radicle generation by immunocompetent carcinoma blood cells of Lewis lung in mice this opens a huge area of application for kaolin usage in restorative cancer treatment. Their antitumor property has made it a potential candidate under investigation [92, 100, 110–112]. Minerals like zincite, talc, rutile, hydrozincite, smithsonite, kaolinite, and smectites are used as an protective agent in skin to prevent against certain external environmental condition and pathogens. They have suitable properties like high sorption, noncytotoxic, little antiseptic and bactericidal as discussed above. They are used as creams, powders, and ointments (REINOL drygard, DP1, kerodex 51, etc.). They are also incorporated in sunscreen formulation to prevent against harmful UV-A and UV-B. Minerals like rutile and zincite absorb, reflect, and scatter the radiation but they may cause skin damage by photocatalytic action this can be overcome by using kaolin as protectant since it shows higher UV protection capacity due to the high Fe2O3 content. Kaolin also used to absorb excess moisture, oily secretion, surface lipids, and superficial toxin from the skin surface to prevent acne, blackheads, bacterial, and fungal infections. Even they are used for insect bites to give relieving effect [109].

### **3.8 Skin protectant**

Sulfur containing minerals are extensively used as keratolytic reducers as they are effective against dermatitis, eczemas, and psoriasis. Sulfur reacts with cysteine in the presence of keratinocyte producing hydrogen sulphide which breaks down keratin. Dandruff is treated with cadmium sulphide shampoo. The less common adverse effect of sulfur applied as topical cream is an added advantage [82]. Isotonic collyrium contains dissolved halite which is used as decongestive eye drops for treating eye dryness, irritation, and other ocular discomforts.

### **4. Use of clay as a drug delivery system**

An effective drug delivery system is essential for achieving proper bioavailability of the drug administered. Recent studies have paved way for many new modified drug delivery system that has led to sustained drug deliver, controlled drug delivery, and site-specific drug delivery (**Table 2**). Each has its own mode of release and application in the body. The modification can be made only through excipients employed. The proposed excipients must possess good delivery efficiency at the same time have inertness, easy availability, cost effective, and low toxicity. Thus, all these are readily available in clay minerals and their physiochemical properties make them a potential candidate for design of MDDS. Clay minerals either in their

**111**

*Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

**4.1 As release retardant**

to aid their use as a drug carrier for delivering system.

native form or modified in certain way to improve their physiochemical properties

Kaolin (1:1) and smectite (1:2) are the most common used clay groups in the design of MDDS due to their geometrical structure. The side effects like short half-life and requirement of frequent dosage in diclofenac sodium (NSAID) can overcome by intercalating it with MMT that prolong drug release. The toxicity of topically administered chlorhexidine (antibiotic) can be prevented by using Na-MMT as a drug delivery carrier. The photolytic damage of promethazine (antihistamine) when administered topically is reduced by intercalation of drug with Na-MMT. The in vitro activity and controlled release of paclitaxel (anticancer) is increased by intercalation with Na-MMT and coating with chitosan (biopolymer). Gallic acid has various properties like poor solubility, permeability, and faster metabolism which make it difficult for dose administration and drug release. The idea of Gallic acid with MMT was suggested and carried to and characterized the drug release profile which showed promising results. A dermal patch prepared using MMT-Na loaded with silver (antimicrobial agent), lidocaine (mild analgesic), and betaine hydrochloride showed a controlled release of lidocaine. The controlled drug release of metformin with Na-MMT was studied in order to reduce the side effect and dosage of drug. But the study concluded that the drug release was highly pH dependent and needed further analysis. MMT enhanced the antibacterial activity with TiO2 coated with alginate against both gram positive and negative bacteria. Mesalazine (5-Aminosalicylic acid) must reach colon to show its therapeutic action against Crohn's disease but mesalazine is highly absorbed in the acidic environment of stomach. This can be altered and slow drug dissolution in stomach was achieved using MMT-Na encapsulated into alginate beads. Acidification improves clay surface area and increases pores for sorption. These acidified clays was used as a carrier to deliver ciprofloxacin, the acid treatment retarded the drug release due to the changes in the interlayer charges, this also provided insight on the usage of interlayer charge modifications of the clays can be a useful phenomenon for drug delivery. Silver nanoparticles are also loaded with modified clay and their antibacterial activity is characterized and a comparative study between modified and unmodified clay hybrid for their loading capacity and antibacterial activity against *S. aureus* and *E. coli* was done. The results showed that both the loading capacity and antibacterial activity was higher for acidified clay when compared to its native form. Periodontal extended release of tetracycline was achieved by intercalation of drug with MMT hybrid (Veegum HV) and chitosan as mucoadhesive base, the formulation required only once per week. Optimization of gentamycin loaded with another clay hybrid (Veegum F) was done and its antibacterial activity was evaluated, the formulation a delayed drug release up until 8 days. Theophylline was loaded onto MMT hybrid (Veegum F) to prevent the premature gastric drug absorption and to give a sustained release in intestine. Electrostatic interaction with clay hybrid prevents theophylline absorption at the stomach pH and facilitates slower absorption on the intestinal pH. The in vitro antibacterial activity of ciprofloxacin was determined by the type of interaction it forms with the clay hybrid, a weak interaction ensures easier release of drug into the desired site. Another modification of clay minerals which is used in MDDS is functionalization of the interlayers. One such functionalized clay is pillared clay which have large specific surface area and larger porosity due to the cationic exchange with inorganic compounds (4-(dimethylamino)-1-(4-vinylbenzyl) pyridiniumchloride and 1-methyl-3-(4-vinylbenzyl) imidazolium chloride). Ibuprofen loaded into MMT

native form or modified in certain way to improve their physiochemical properties to aid their use as a drug carrier for delivering system.

### **4.1 As release retardant**

*Clay Science and Technology*

fying agent.

effect [109].

**3.8 Skin protectant**

**3.7 Miscellaneous**

that amino acid and carboxylic residue present on the outer shell viral protein coat is responsible for the net charge and their adsorption into clay minerals depends on pH, ionic strength, and isoelectric points of the clay and virus. Further studies show that hydrophobic interactions of crystallized kaolin show greater affinity for certain bacteriophages. In vitro studies of kaolin against hepatitis C virus, human enteric pathogenic adenoviruses (hAdVs) and adenovirus (HAdV-5) proved kaolin to be an effective material that could be used against certain viral infections [110]. Many substances like heavy metals, toxins, mycotoxins, and overdosed drug compounds can be removed from the gastrointestinal tract by administering kaolin as a detoxi-

Kaolin is found to influence superoxide radicle generation by immunocompetent carcinoma blood cells of Lewis lung in mice this opens a huge area of application for kaolin usage in restorative cancer treatment. Their antitumor property has made it a potential candidate under investigation [92, 100, 110–112]. Minerals like zincite, talc, rutile, hydrozincite, smithsonite, kaolinite, and smectites are used as an protective agent in skin to prevent against certain external environmental condition and pathogens. They have suitable properties like high sorption, noncytotoxic, little antiseptic and bactericidal as discussed above. They are used as creams, powders, and ointments (REINOL drygard, DP1, kerodex 51, etc.). They are also incorporated in sunscreen formulation to prevent against harmful UV-A and UV-B. Minerals like rutile and zincite absorb, reflect, and scatter the radiation but they may cause skin damage by photocatalytic action this can be overcome by using kaolin as protectant since it shows higher UV protection capacity due to the high Fe2O3 content. Kaolin also used to absorb excess moisture, oily secretion, surface lipids, and superficial toxin from the skin surface to prevent acne, blackheads, bacterial, and fungal infections. Even they are used for insect bites to give relieving

Sulfur containing minerals are extensively used as keratolytic reducers as they are effective against dermatitis, eczemas, and psoriasis. Sulfur reacts with cysteine in the presence of keratinocyte producing hydrogen sulphide which breaks down keratin. Dandruff is treated with cadmium sulphide shampoo. The less common adverse effect of sulfur applied as topical cream is an added advantage [82]. Isotonic collyrium contains dissolved halite which is used as decongestive eye drops for

An effective drug delivery system is essential for achieving proper bioavailability of the drug administered. Recent studies have paved way for many new modified drug delivery system that has led to sustained drug deliver, controlled drug delivery, and site-specific drug delivery (**Table 2**). Each has its own mode of release and application in the body. The modification can be made only through excipients employed. The proposed excipients must possess good delivery efficiency at the same time have inertness, easy availability, cost effective, and low toxicity. Thus, all these are readily available in clay minerals and their physiochemical properties make them a potential candidate for design of MDDS. Clay minerals either in their

treating eye dryness, irritation, and other ocular discomforts.

**4. Use of clay as a drug delivery system**

**110**

Kaolin (1:1) and smectite (1:2) are the most common used clay groups in the design of MDDS due to their geometrical structure. The side effects like short half-life and requirement of frequent dosage in diclofenac sodium (NSAID) can overcome by intercalating it with MMT that prolong drug release. The toxicity of topically administered chlorhexidine (antibiotic) can be prevented by using Na-MMT as a drug delivery carrier. The photolytic damage of promethazine (antihistamine) when administered topically is reduced by intercalation of drug with Na-MMT. The in vitro activity and controlled release of paclitaxel (anticancer) is increased by intercalation with Na-MMT and coating with chitosan (biopolymer). Gallic acid has various properties like poor solubility, permeability, and faster metabolism which make it difficult for dose administration and drug release. The idea of Gallic acid with MMT was suggested and carried to and characterized the drug release profile which showed promising results. A dermal patch prepared using MMT-Na loaded with silver (antimicrobial agent), lidocaine (mild analgesic), and betaine hydrochloride showed a controlled release of lidocaine. The controlled drug release of metformin with Na-MMT was studied in order to reduce the side effect and dosage of drug. But the study concluded that the drug release was highly pH dependent and needed further analysis. MMT enhanced the antibacterial activity with TiO2 coated with alginate against both gram positive and negative bacteria. Mesalazine (5-Aminosalicylic acid) must reach colon to show its therapeutic action against Crohn's disease but mesalazine is highly absorbed in the acidic environment of stomach. This can be altered and slow drug dissolution in stomach was achieved using MMT-Na encapsulated into alginate beads. Acidification improves clay surface area and increases pores for sorption. These acidified clays was used as a carrier to deliver ciprofloxacin, the acid treatment retarded the drug release due to the changes in the interlayer charges, this also provided insight on the usage of interlayer charge modifications of the clays can be a useful phenomenon for drug delivery. Silver nanoparticles are also loaded with modified clay and their antibacterial activity is characterized and a comparative study between modified and unmodified clay hybrid for their loading capacity and antibacterial activity against *S. aureus* and *E. coli* was done. The results showed that both the loading capacity and antibacterial activity was higher for acidified clay when compared to its native form. Periodontal extended release of tetracycline was achieved by intercalation of drug with MMT hybrid (Veegum HV) and chitosan as mucoadhesive base, the formulation required only once per week. Optimization of gentamycin loaded with another clay hybrid (Veegum F) was done and its antibacterial activity was evaluated, the formulation a delayed drug release up until 8 days. Theophylline was loaded onto MMT hybrid (Veegum F) to prevent the premature gastric drug absorption and to give a sustained release in intestine. Electrostatic interaction with clay hybrid prevents theophylline absorption at the stomach pH and facilitates slower absorption on the intestinal pH. The in vitro antibacterial activity of ciprofloxacin was determined by the type of interaction it forms with the clay hybrid, a weak interaction ensures easier release of drug into the desired site. Another modification of clay minerals which is used in MDDS is functionalization of the interlayers. One such functionalized clay is pillared clay which have large specific surface area and larger porosity due to the cationic exchange with inorganic compounds (4-(dimethylamino)-1-(4-vinylbenzyl) pyridiniumchloride and 1-methyl-3-(4-vinylbenzyl) imidazolium chloride). Ibuprofen loaded into MMT

hybrid pillarized with Fe3+ and Fe2+ showed a delay in drug release under various physiological conditions. Doxorubicin (anticancer) was loaded into functionalized kaolin showed good drug loading efficiency and therapeutic action.

### **4.2 Clay-biopolymer combination**

Biopolymers can also influence drug delivery by encapsulation or by surface coating over the formulation and help in controlled drug delivery. Hence, clay hybrids are coated with biopolymers to enhance their action. Clay hybrid and biopolymer (chitosan) showed synergistic effect on loading efficiency and drug release of 5-aminosalicylic acid. The oral bioavailability of oxytetracycline (broad spectrum antibiotic) was improved by loading over chitosan-MMT carrier. The cytotoxicity of chlorohexine to fibroblast was reduced by preparing a film carrier made of MMT-chitosan complex. The prepared topical formulation showed a controlled release of drug and reduction of cytotoxicity was also reported. MMT-chitosan glutamate composites also reduced the cytotoxic effects of silver sulfadiazine (skin burns). The result show that electrostatic interaction of MMT with polymer helps improving the drug absorption and the increase an antibacterial activity of formulation was also noted. Apart from chitosan, other biopolymers have been used to prepare drug carriers. A combination of guar gum-MMT hybrid was used to prepare a controlled release formulation of ibuprofen to reduce their side effects on intestinal tracts. The need of frequent dosage of venlafaxine (anti-depressive drug) was reduced by preparing beads with crosslinking of sodium ALG with drug-MMT in CaCl2. Olanzapine (schizophrenia and bipolar disorder) was incorporated into different polymer composition and their drug release at different pH was studied and the results were in comparison with the marked drug and an effective controlled release was obtained by cloisite-drug with a blend of polymers (Alginate and xanthan gum). The solubility of curcumin (anticancer, anti-inflammatory and antibacterial agent) can be increased by dispersing the drug with CMC and loading into MMT, the role of MMT here is to improve the drug release in the acidic environment. A transdermal DDS was prepared from MMT nanocomposite, pectin, and methyl cellulose which is used to load ketorolac (NSAID). The formulations showed immediate release of drug from the nanocomposite layer but the increase in MMT showed controlled drug release. The PLA microspheres of 6-mercaptopurine (anticancer drug) with MMT showed a faster release rate and increased the drug solubility. The presence MMT also helps to control the drug release. The performance of a pH dependent swelling polymer (poly acrylamide-co-maleic acid) was improved by the addition of MMT hybrid, it exerted a control over the caffeine drug release even during sudden pH transitions. A prolonged oral DDS was prepared for 1,3,4-oxa(thia)diazole (antifungal, antibiotic, analgesic and anti-inflammatory agent) by preparing nanocomposite using MMT hybrid. A site specific DDS was developed using MMT-polymer hybrid for anticancer treatment by co administration of doxorubicin and methotrexate with ciprofloxacin (antibiotic). Specificity of the DDS depends on the pH of the tumor cells. The results showed that the entire three drugs exhibit delayed drug release, where the anticancer drugs showed similar release profile and ciprofloxacin showed a different release profile at pH 5.8 and 4. PLGA is another biopolymer which is extensively used as carrier for drug administration. A double emulsion of atenolol with PLGA and MMT was prepared by Lal and Datta to increase the half-life and dissolution rate of the drug. The result suggested a controlled drug release in both acidic as well as basic medium with marking changes in the acidic medium. The hydrophobic drug (dexamethasone) was also intercalated with PLGA and MMT by Jain and Datta to lower the risk of side effects and achieve effective plasma concentration at minimal dosage. PLGS-MMT

**113**

loaded with anticancer drugs.

*Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

nanocomposite is used as a carrier for insulin. In vitro studies by Lal et al. suggested the protective nature of MMT even in acidic conditions and also they do not affect the HEK-293 cells growth. A triblock (PCLA-PEG-PCLA) copolymer hydrogel of MMT-gemcitabine (anticancer) was prepared for the intravenous administration of drug since the drug is metabolized rapidly and require high dose. In vitro drug release studies suggested that MMT significantly reduced the drug release and the side effects. Nanocomposite of MMT hybrid with HEMA was used to modify the dissolution profile of paracetamol by Bounabi et al. The inclusion of MMT improved the drug encapsulation of paracetamol in the PLA-drug nanocomposite. A site specific DDS was prepared for doxorubicin was prepared using MMT hybrid with PE-5000/PEG750 polymer. Organoclay (MMT-PVP hybrid) nanocomposite was used to encapsulate copaiba oleoresin a natural derivative used against endometriosis. The nanocomposite showed effective controlled drug release at acidic pH. A polymeric composite (PVA, CS and MMT) was prepared to encapsulate 5-flurouracil (anticancer) in order to compensate its poor oral absorption and rapid metabolism. The results also indicate that the drug loading efficiency and drug release depends on the MMT concentration. Clay minerals like halosite and fibrous phyllosilicates have MMDS application due to their tubular and ribbon shaped structure. For example, the Hal nanotubes can adapt to any morphology making them used for wide variety of applications in MDDS. Various antibiotic like ciprofloxacin, chlorpheniramine, tetracycline, diphenhydramine has been loaded on to the hal nanotubes and investigated. Cationic exchange capacity and pH determines the drug loading capacity on to the hal nanotubes. Thermodynamic equilibrium also affect the drug loading in hal nanotubes as in the case of isoniazid (antituberculosis drug). The immobilization of binase (RNase enzyme) which is used in the genetic treatment of cancer was done and an enhanced anticancer property was reported. Vancomycin and breviscapine has been loaded on to hal nanotubes by vacuum cycle and the resultant complex showed a sustained release of drugs. Amoxicillin loaded onto Hal nanotubes are combined with biopolymers (PLGA and Chitosan) and the drug release was studied the results suggest a sustained release is obtained on both formulations with and without biopolymers than biopolymerdrug complex. PMMA was coated onto paclitaxel-hal nanotube complex to improve the anticancer activity of the drug. Volatile drugs are also adsorbed onto the clay minerals which help in preventing the evaporation of those drugs and retaining their therapeutic action. The volatile drug absorption of MMT, hal nanotubes and palygorskite was evaluated by loading carvacrol (treat skin lesions). Good adsorption was seen in palygorskite. Veegum HS and sepiolite improved the solubility and dissolution rate of praziquantel (treatment of schistosomiasis) in both acidic and basic environment. Higher dissolution was achieved by oxaprozin (Non-steroidal anti-inflammatory agent) on mixing it with clay hybrid of palygorskite and sepiolite modified with cyclodextrin. Curcumin was loaded with both functionalized clay and cellulose-MMT complex to improve its site specific action and synergic effect on wound healing. A phospholipid nanocomposite of hal nanotubes was prepared to achieve a sustained release of doxorubicin. The electrostatic interaction and intermolecular hydrogen bonding between palygorskite and chitosan was studied for its usage as a drug carrier for 5-aminosalicylic acid. Sepiolite is also used with chitosan as drug carrier for tetracycline and cefazolin. In vitro studies show the swelling of gel is facilitated by chitosan whereas the drug release id controlled by crosslinking of polyvinylacryalate (PVA). The synergistic effect of hydroxypropylmethylcellouse acetate succinate along with atorvastatin and celecoxib for colon cancer is due to their effective solubility in basic pH. The controlled release of drug in colon is achieved by the preparing microspheres of hal nanotubes and HPMCAS

### *Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

*Clay Science and Technology*

**4.2 Clay-biopolymer combination**

hybrid pillarized with Fe3+ and Fe2+ showed a delay in drug release under various physiological conditions. Doxorubicin (anticancer) was loaded into functionalized

Biopolymers can also influence drug delivery by encapsulation or by surface coating over the formulation and help in controlled drug delivery. Hence, clay hybrids are coated with biopolymers to enhance their action. Clay hybrid and biopolymer (chitosan) showed synergistic effect on loading efficiency and drug release of 5-aminosalicylic acid. The oral bioavailability of oxytetracycline (broad spectrum antibiotic) was improved by loading over chitosan-MMT carrier. The cytotoxicity of chlorohexine to fibroblast was reduced by preparing a film carrier made of MMT-chitosan complex. The prepared topical formulation showed a controlled release of drug and reduction of cytotoxicity was also reported. MMT-chitosan glutamate composites also reduced the cytotoxic effects of silver sulfadiazine (skin burns). The result show that electrostatic interaction of MMT with polymer helps improving the drug absorption and the increase an antibacterial activity of formulation was also noted. Apart from chitosan, other biopolymers have been used to prepare drug carriers. A combination of guar gum-MMT hybrid was used to prepare a controlled release formulation of ibuprofen to reduce their side effects on intestinal tracts. The need of frequent dosage of venlafaxine (anti-depressive drug) was reduced by preparing beads with crosslinking of sodium ALG with drug-MMT in CaCl2. Olanzapine (schizophrenia and bipolar disorder) was incorporated into different polymer composition and their drug release at different pH was studied and the results were in comparison with the marked drug and an effective controlled release was obtained by cloisite-drug with a blend of polymers (Alginate and xanthan gum). The solubility of curcumin (anticancer, anti-inflammatory and antibacterial agent) can be increased by dispersing the drug with CMC and loading into MMT, the role of MMT here is to improve the drug release in the acidic environment. A transdermal DDS was prepared from MMT nanocomposite, pectin, and methyl cellulose which is used to load ketorolac (NSAID). The formulations showed immediate release of drug from the nanocomposite layer but the increase in MMT showed controlled drug release. The PLA microspheres of 6-mercaptopurine (anticancer drug) with MMT showed a faster release rate and increased the drug solubility. The presence MMT also helps to control the drug release. The performance of a pH dependent swelling polymer (poly acrylamide-co-maleic acid) was improved by the addition of MMT hybrid, it exerted a control over the caffeine drug release even during sudden pH transitions. A prolonged oral DDS was prepared for 1,3,4-oxa(thia)diazole (antifungal, antibiotic, analgesic and anti-inflammatory agent) by preparing nanocomposite using MMT hybrid. A site specific DDS was developed using MMT-polymer hybrid for anticancer treatment by co administration of doxorubicin and methotrexate with ciprofloxacin (antibiotic). Specificity of the DDS depends on the pH of the tumor cells. The results showed that the entire three drugs exhibit delayed drug release, where the anticancer drugs showed similar release profile and ciprofloxacin showed a different release profile at pH 5.8 and 4. PLGA is another biopolymer which is extensively used as carrier for drug administration. A double emulsion of atenolol with PLGA and MMT was prepared by Lal and Datta to increase the half-life and dissolution rate of the drug. The result suggested a controlled drug release in both acidic as well as basic medium with marking changes in the acidic medium. The hydrophobic drug (dexamethasone) was also intercalated with PLGA and MMT by Jain and Datta to lower the risk of side effects and achieve effective plasma concentration at minimal dosage. PLGS-MMT

kaolin showed good drug loading efficiency and therapeutic action.

**112**

nanocomposite is used as a carrier for insulin. In vitro studies by Lal et al. suggested the protective nature of MMT even in acidic conditions and also they do not affect the HEK-293 cells growth. A triblock (PCLA-PEG-PCLA) copolymer hydrogel of MMT-gemcitabine (anticancer) was prepared for the intravenous administration of drug since the drug is metabolized rapidly and require high dose. In vitro drug release studies suggested that MMT significantly reduced the drug release and the side effects. Nanocomposite of MMT hybrid with HEMA was used to modify the dissolution profile of paracetamol by Bounabi et al. The inclusion of MMT improved the drug encapsulation of paracetamol in the PLA-drug nanocomposite. A site specific DDS was prepared for doxorubicin was prepared using MMT hybrid with PE-5000/PEG750 polymer. Organoclay (MMT-PVP hybrid) nanocomposite was used to encapsulate copaiba oleoresin a natural derivative used against endometriosis. The nanocomposite showed effective controlled drug release at acidic pH. A polymeric composite (PVA, CS and MMT) was prepared to encapsulate 5-flurouracil (anticancer) in order to compensate its poor oral absorption and rapid metabolism. The results also indicate that the drug loading efficiency and drug release depends on the MMT concentration. Clay minerals like halosite and fibrous phyllosilicates have MMDS application due to their tubular and ribbon shaped structure. For example, the Hal nanotubes can adapt to any morphology making them used for wide variety of applications in MDDS. Various antibiotic like ciprofloxacin, chlorpheniramine, tetracycline, diphenhydramine has been loaded on to the hal nanotubes and investigated. Cationic exchange capacity and pH determines the drug loading capacity on to the hal nanotubes. Thermodynamic equilibrium also affect the drug loading in hal nanotubes as in the case of isoniazid (antituberculosis drug). The immobilization of binase (RNase enzyme) which is used in the genetic treatment of cancer was done and an enhanced anticancer property was reported. Vancomycin and breviscapine has been loaded on to hal nanotubes by vacuum cycle and the resultant complex showed a sustained release of drugs. Amoxicillin loaded onto Hal nanotubes are combined with biopolymers (PLGA and Chitosan) and the drug release was studied the results suggest a sustained release is obtained on both formulations with and without biopolymers than biopolymerdrug complex. PMMA was coated onto paclitaxel-hal nanotube complex to improve the anticancer activity of the drug. Volatile drugs are also adsorbed onto the clay minerals which help in preventing the evaporation of those drugs and retaining their therapeutic action. The volatile drug absorption of MMT, hal nanotubes and palygorskite was evaluated by loading carvacrol (treat skin lesions). Good adsorption was seen in palygorskite. Veegum HS and sepiolite improved the solubility and dissolution rate of praziquantel (treatment of schistosomiasis) in both acidic and basic environment. Higher dissolution was achieved by oxaprozin (Non-steroidal anti-inflammatory agent) on mixing it with clay hybrid of palygorskite and sepiolite modified with cyclodextrin. Curcumin was loaded with both functionalized clay and cellulose-MMT complex to improve its site specific action and synergic effect on wound healing. A phospholipid nanocomposite of hal nanotubes was prepared to achieve a sustained release of doxorubicin. The electrostatic interaction and intermolecular hydrogen bonding between palygorskite and chitosan was studied for its usage as a drug carrier for 5-aminosalicylic acid. Sepiolite is also used with chitosan as drug carrier for tetracycline and cefazolin. In vitro studies show the swelling of gel is facilitated by chitosan whereas the drug release id controlled by crosslinking of polyvinylacryalate (PVA). The synergistic effect of hydroxypropylmethylcellouse acetate succinate along with atorvastatin and celecoxib for colon cancer is due to their effective solubility in basic pH. The controlled release of drug in colon is achieved by the preparing microspheres of hal nanotubes and HPMCAS loaded with anticancer drugs.

### **5. Pharmaceutical clay in share market**

The clay minerals are exported worldwide for their various applications in construction and pharmaceutical preparations. Based of the application the clay mineral export is classified as tableware, sanitary ware, medicinal applications. The key minerals are bentonite and kaolin which accounts for major export. Bentonite is exported as sodium, calcium and sulfur bentonite. The global market demand of bentonite (**Figure 2a** and **b**) was 22.68 million metric ton by 2016 and estimated to be 25.15 Million metric ton by 2021 with a CAGR increase of 2.12%. The global market share of bentonite by 2017 was 1.43 billion and estimated to be increasing scale due to the market demand and increase in the applications of clay minerals. The major region of export is classified as Asia Pacific, North America, Europe and Rest of the world with Asia and North America accounting for most. The major companies exporting clay minerals are Ashapura groups (India's major exporter), Imerys(sandB), Taiko group, Huawei Bentonite, Theile kaolin company, Kaolin A.D, J.M.Huber, Daleco resources.

**Figure 2.**

*(a) Bentonite classification based on minerals. (b) Bentonite usage on global demand scale.*

### **6. Conclusion and outlook**

From the moment of discovery clay minerals have been immensely useful to human life in both ceramic and health. Their usage in health care has made it a essential compound in many pharmaceutical preparations. Their inertness, low toxicity, versatile physiochemical properties and cost effectiveness has increased its usage in pharma industries. At the same time precautions must be taken while incorporating higher doses of clay and while co-administering clay with drug. Since some clay has been reported to reduce the efficacy and bioavailability of certain classes of drugs like antacid and in higher doses it might cause tissue toxicity. The understanding of surface chemistry and particle size distribution of clay minerals has led the pharmaceutical field in many directions and future perspectives. Their unique structure which helps them to absorb material onto their layered sheets has opened a wide variety of applications in drug delivery. Their ability to control and alter drug release profile can been exploited in many ways to design a effective drug delivery system. Further advancements in nanotechnology have helped to synthesize and modify this clay mineral to enhance their physiochemical properties and their usage as excipient. Though clay and their minerals are used in its natural

**115**

**Author details**

Sekar Krishnaraj3

India

Nandakumar Selvasudha1

and Irisappan Sarathchandiran1

and dhanamnair2013@gmail.com

provided the original work is properly cited.

\*, Unnikrishnan-Meenakshi Dhanalekshmi<sup>2</sup>

, Yogeeswarakannan Harish Sundar3

2 Oman Medical College, Bowshar Campus, Muscat, Sultanate of Oman

3 Department of Biotechnology, Anna University, Chennai, India

\*Address all correspondence to: nkselvasudha@gmail.com

1 School of Pharmacy, Sri Balaji Vidyapeeth Deemed to be University, Puducherry,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

state for drug delivery, some require additional modification for their usage and this modification plays a key role in determining the economical aspect of drug designing. The development of machinery which helps us to understand better about various unknown properties of clay minerals which were not understood before will

aid us to utilize clay minerals in various other applications.

\*,

, Nagarajan Sri Durga Devi3

*Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

### *Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

*Clay Science and Technology*

**5. Pharmaceutical clay in share market**

A.D, J.M.Huber, Daleco resources.

**6. Conclusion and outlook**

**Figure 2.**

The clay minerals are exported worldwide for their various applications in construction and pharmaceutical preparations. Based of the application the clay mineral export is classified as tableware, sanitary ware, medicinal applications. The key minerals are bentonite and kaolin which accounts for major export. Bentonite is exported as sodium, calcium and sulfur bentonite. The global market demand of bentonite (**Figure 2a** and **b**) was 22.68 million metric ton by 2016 and estimated to be 25.15 Million metric ton by 2021 with a CAGR increase of 2.12%. The global market share of bentonite by 2017 was 1.43 billion and estimated to be increasing scale due to the market demand and increase in the applications of clay minerals. The major region of export is classified as Asia Pacific, North America, Europe and Rest of the world with Asia and North America accounting for most. The major companies exporting clay minerals are Ashapura groups (India's major exporter), Imerys(sandB), Taiko group, Huawei Bentonite, Theile kaolin company, Kaolin

From the moment of discovery clay minerals have been immensely useful to human life in both ceramic and health. Their usage in health care has made it a essential compound in many pharmaceutical preparations. Their inertness, low toxicity, versatile physiochemical properties and cost effectiveness has increased its usage in pharma industries. At the same time precautions must be taken while incorporating higher doses of clay and while co-administering clay with drug. Since some clay has been reported to reduce the efficacy and bioavailability of certain classes of drugs like antacid and in higher doses it might cause tissue toxicity. The understanding of surface chemistry and particle size distribution of clay minerals has led the pharmaceutical field in many directions and future perspectives. Their unique structure which helps them to absorb material onto their layered sheets has opened a wide variety of applications in drug delivery. Their ability to control and alter drug release profile can been exploited in many ways to design a effective drug delivery system. Further advancements in nanotechnology have helped to synthesize and modify this clay mineral to enhance their physiochemical properties and their usage as excipient. Though clay and their minerals are used in its natural

*(a) Bentonite classification based on minerals. (b) Bentonite usage on global demand scale.*

**114**

state for drug delivery, some require additional modification for their usage and this modification plays a key role in determining the economical aspect of drug designing. The development of machinery which helps us to understand better about various unknown properties of clay minerals which were not understood before will aid us to utilize clay minerals in various other applications.

### **Author details**

Nandakumar Selvasudha1 \*, Unnikrishnan-Meenakshi Dhanalekshmi<sup>2</sup> \*, Sekar Krishnaraj3 , Yogeeswarakannan Harish Sundar3 , Nagarajan Sri Durga Devi3 and Irisappan Sarathchandiran1

1 School of Pharmacy, Sri Balaji Vidyapeeth Deemed to be University, Puducherry, India

2 Oman Medical College, Bowshar Campus, Muscat, Sultanate of Oman

3 Department of Biotechnology, Anna University, Chennai, India

\*Address all correspondence to: nkselvasudha@gmail.com and dhanamnair2013@gmail.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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*Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

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[75] Panchagnula R, Bhardwaj V. Effect of amorphous content on dissolution characteristics of rifampicin. Drug Development and Industrial Pharmacy. 2008;**34**:642-649

[76] Qi S, McAuley WJ, Yang Z, Tipduangta P. Physical stabilization of low-molecular weight amorphous drugs in the solid state: A material science approach. Therapeutic Delivery. 2014;**5**(7):817-841

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[80] Felton LA, Porter SC. An update on pharmaceutical film coating for drug delivery. Expert Opinion on Drug Delivery. 2013;**10**(4):421-435

[81] Zoglio MA, Maulding HV, Carstensen JT. Linearization of drug delivery from sustained-release dosage forms, synthetic gel systems. Drug Development and Industrial Pharmacy. 1996;**22**(5):431-437

[82] Carretero MI, Pozo M. Clay and non-clay minerals in the pharmaceutical and cosmetic industries. Part II. Active ingredients. Applied Clay Science. 2010;**47**:171-181

[83] Hermans MH. Wounds and ulcers: Back to the old nomenclature. Wounds. 2010;**22**(11):289-293

[84] Glick JB, Kaur RR, Siegel D. Achieving hemostasis in dermatology – Part II: Topical hemostatic agents. Indian Dermatology Online Journal. 2013;**4**(3):172-176

[85] Smith AH, Laird C, Porter K, Bloch M. Haemostatic dressings in prehospital care. Emergency Medicine Journal. 2013;**30**:784-789

[86] Pourshahrestani S, Zeimaran E, Djordjevic I, Kadri NA, Towler MR. Inorganic hemostats: The state-ofthe-art and recent advances. Materials

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[95] Christidis GE, Scott PW, Dunham AC. Acid activation and bleaching capacity of bentonites from the islands of Milos and Chios, Aegean, Greece. Applied Clay Science.

[96] Vicente Rodríguez MA, López González JD, Bañares Muñoz MA. Acid activation of a Spanish sepiolite: Physicochemical characterization, free silica content and surface area of products obtained. Clay Minerals.

[97] Aparicio P, Galán E. Mineralogical interference on kaolinite crystallinity index measurement. Clays and Clay

[98] Clark A, Ede R. Acute Diarrhoea:

Management. 2011. Available from: www.prescriber.co.uk [Accessed: 12

[99] Primandini P, Hasanah AN, Adi WA, Budianto E, Sudirman S. The effect of calcination temperature on toxin adsorption materials for diarrheal

diseases. Indonesian Journal of Materials Science. 2012;**13**(3):230-235

[101] Pieszka M, Luszczynski J, Hedrzak M, Goncharova K, Pierzynowski SG. The efficacy of kaolin clay in reducing the duration and severity of heat' diarrhea in foals. Turkish Journal of Veterinary and Animal Sciences. 2016;**40**(3):323-328

[100] Wardhana YW, Hasanah AN, Primandini P. Deformation and adsorption capacity of kaolin that is influenced by temperature variation on calcination. International Journal of Pharmacy and Pharmaceutical Sciences.

pp. 631-674

1997;**12**:329-347

1994;**29**:361-367

September 2017]

2014;**6**(3):1-2

Minerals. 1999;**47**:12-27

Causes and Recommended

[88] Droy-Lefaix MT, Tateo F. Clays and clay minerals as drugs. In: Bergaya F, Theng BKG, Lagaly G, editors. Handbook of Clay Science. Amsterdam: Elsevier; 2006. pp. 743-752

[89] Leonard AJ, Droy-Lefaix MT, Allen A. Pepsin hydrolysis of the adherent mucus barrier and subsequent gastric mucosal damage in the rat: Effect of diosmectite and 16, 16 dimethyl prostaglandin E2. Gastroentérologie Clinique et Biologique. 1994;**8**:609-616

[90] Rozalen M, Huertas FJ, Brady PV. Experimental study of the effect of pH and temperature on the kinetics of montmorillonite dissolution. Geochimica et Cosmochimica Acta.

[91] Habold C, Reichardt F, Le Maho Y, Angel F, Liewig N, Lignot J, et al. Clay ingestion enhances intestinal triacylglycerol hydrolysis and nonesterified fatty acid absorption. British Journal of Nutrition. 1985;**102**:249-257

[92] Kikouama OJR, Balde L. From edible clay to a clay-containing formulation for optimization of oral delivery of some trace elements: A review. International Journal of Food Sciences and Nutrition.

2009;**73**:3752-3766

2010;**61**(8):803-822

2011;**104**:659-665

[93] Constancio J, Pereira-

Derderian DTB, Menani JV, De Luca Jr LA. Mineral intake independent from gastric irritation or pica by celldehydrated rats. Physiology & Behavior.

[94] Jones BF, Galán E. Sepiolite and palygorskite. In: Bailey SW, editor. Hydrous Phyllosilicates. Reviews in

Science and Engineering: C.

2016;**58**:1255-1268

*Multifunctional Clay in Pharmaceuticals DOI: http://dx.doi.org/10.5772/intechopen.92408*

Science and Engineering: C. 2016;**58**:1255-1268

*Clay Science and Technology*

1997;**14**(5):647-657

1996;**132**:131-141

2015;**5**(1):55-63

1996;**22**(4):357-371

2008;**34**:642-649

2014;**5**(7):817-841

[71] Agrawal R, Naveen Y.

[69] Law MFL, Deasy PB. Effect of common classes of excipients on extrusion spheronization. Journal of Microencapsulation.

applications. Applied Clay Science.

In: Harry RG, editor. Harry's Cosmeticology. The Principles and Practice of Modern Cosmetics. Vol. I. 6th ed. London: Leonard Hill Books.

of insoluble excipients on film coating systems. Drug Development

and Industrial Pharmacy. 2002;**28**(3):225-243

Delivery. 2013;**10**(4):421-435

[81] Zoglio MA, Maulding HV, Carstensen JT. Linearization of drug delivery from sustained-release dosage forms, synthetic gel systems. Drug Development and Industrial Pharmacy.

[82] Carretero MI, Pozo M. Clay and non-clay minerals in the pharmaceutical and cosmetic industries. Part II. Active ingredients. Applied Clay Science.

[83] Hermans MH. Wounds and ulcers: Back to the old nomenclature. Wounds.

[84] Glick JB, Kaur RR, Siegel D. Achieving hemostasis in dermatology – Part II: Topical hemostatic agents. Indian Dermatology Online Journal.

[85] Smith AH, Laird C, Porter K, Bloch M. Haemostatic dressings in prehospital care. Emergency Medicine

[86] Pourshahrestani S, Zeimaran E, Djordjevic I, Kadri NA, Towler MR. Inorganic hemostats: The state-ofthe-art and recent advances. Materials

Journal. 2013;**30**:784-789

1996;**22**(5):431-437

2010;**47**:171-181

2010;**22**(11):289-293

2013;**4**(3):172-176

[78] Wedderburn DL. Baby preparations.

[79] Felton LA, McGinity JW. Influence

[80] Felton LA, Porter SC. An update on pharmaceutical film coating for drug delivery. Expert Opinion on Drug

2009;**46**:73-80

1973:543

[70] Deasy PB, Gouldson MP. In vitro evaluation of pellets containing enteric coprecipitates of nifedipine formed by non-aqueous spheronization. International Journal of Pharmaceutics.

Pharmaceutical processing – A review on wet granulation technology.

International Journal of Pharmaceutical Frontier Research. 2011;**1**(1):65-83

[72] Shanmugam S. Granulation techniques and technologies: Recent progresses. BioImpacts: BI.

[73] Chow AHL, Leung MWM. A study of the mechanisms of wet spherical agglomeration of pharmaceutical powders. Drug

Development and Industrial Pharmacy.

[74] Mallick S, Pattnaik S, Swain K. Current perspectives of solubilization: Potential for improved bioavailability. Drug Development and Industrial Pharmacy. 2007;**33**:865-873

[75] Panchagnula R, Bhardwaj V. Effect of amorphous content on dissolution characteristics of rifampicin. Drug Development and Industrial Pharmacy.

[76] Qi S, McAuley WJ, Yang Z, Tipduangta P. Physical stabilization of low-molecular weight amorphous drugs in the solid state: A material science approach. Therapeutic Delivery.

[77] Carretero MI, Pozo M. Clay and non-clay minerals in the pharmaceutical industry. Part I. Excipients and medical

**120**

[87] Z-Medica. Informative Website of QuikClot® Hemostatic Devices. 2017. Available from: http://www.quikclot. com/ [Accessed: 12 September 2017]

[88] Droy-Lefaix MT, Tateo F. Clays and clay minerals as drugs. In: Bergaya F, Theng BKG, Lagaly G, editors. Handbook of Clay Science. Amsterdam: Elsevier; 2006. pp. 743-752

[89] Leonard AJ, Droy-Lefaix MT, Allen A. Pepsin hydrolysis of the adherent mucus barrier and subsequent gastric mucosal damage in the rat: Effect of diosmectite and 16, 16 dimethyl prostaglandin E2. Gastroentérologie Clinique et Biologique. 1994;**8**:609-616

[90] Rozalen M, Huertas FJ, Brady PV. Experimental study of the effect of pH and temperature on the kinetics of montmorillonite dissolution. Geochimica et Cosmochimica Acta. 2009;**73**:3752-3766

[91] Habold C, Reichardt F, Le Maho Y, Angel F, Liewig N, Lignot J, et al. Clay ingestion enhances intestinal triacylglycerol hydrolysis and nonesterified fatty acid absorption. British Journal of Nutrition. 1985;**102**:249-257

[92] Kikouama OJR, Balde L. From edible clay to a clay-containing formulation for optimization of oral delivery of some trace elements: A review. International Journal of Food Sciences and Nutrition. 2010;**61**(8):803-822

[93] Constancio J, Pereira-Derderian DTB, Menani JV, De Luca Jr LA. Mineral intake independent from gastric irritation or pica by celldehydrated rats. Physiology & Behavior. 2011;**104**:659-665

[94] Jones BF, Galán E. Sepiolite and palygorskite. In: Bailey SW, editor. Hydrous Phyllosilicates. Reviews in

Mineralogy. Vol. 19. Washington, DC: Mineralogical Society of America; 1988. pp. 631-674

[95] Christidis GE, Scott PW, Dunham AC. Acid activation and bleaching capacity of bentonites from the islands of Milos and Chios, Aegean, Greece. Applied Clay Science. 1997;**12**:329-347

[96] Vicente Rodríguez MA, López González JD, Bañares Muñoz MA. Acid activation of a Spanish sepiolite: Physicochemical characterization, free silica content and surface area of products obtained. Clay Minerals. 1994;**29**:361-367

[97] Aparicio P, Galán E. Mineralogical interference on kaolinite crystallinity index measurement. Clays and Clay Minerals. 1999;**47**:12-27

[98] Clark A, Ede R. Acute Diarrhoea: Causes and Recommended Management. 2011. Available from: www.prescriber.co.uk [Accessed: 12 September 2017]

[99] Primandini P, Hasanah AN, Adi WA, Budianto E, Sudirman S. The effect of calcination temperature on toxin adsorption materials for diarrheal diseases. Indonesian Journal of Materials Science. 2012;**13**(3):230-235

[100] Wardhana YW, Hasanah AN, Primandini P. Deformation and adsorption capacity of kaolin that is influenced by temperature variation on calcination. International Journal of Pharmacy and Pharmaceutical Sciences. 2014;**6**(3):1-2

[101] Pieszka M, Luszczynski J, Hedrzak M, Goncharova K, Pierzynowski SG. The efficacy of kaolin clay in reducing the duration and severity of heat' diarrhea in foals. Turkish Journal of Veterinary and Animal Sciences. 2016;**40**(3):323-328

[102] López-Galindo A, Viseras C. Pharmaceutical and cosmetic applications of clays. In: Wypych F, Satyanarayana KG, editors. Clay Surfaces: Fundamentals and Applications. Amsterdam: Elsevier Academic Press; 2004. pp. 267-289

[103] Medzhitov R. Origin and physiological roles of inflammation. Nature. 2008;**454**:428-435

[104] Charkoudian N. Mechanisms and modifiers of reflex induced cutaneous vasodilation and vasoconstriction in humans. Journal of Applied Physiology. 2010;**109**:1221-1228

[105] Cornejo-Garrido H, Nieto-Camacho A, Gómez-Vidales V, Ramírez-Apan MT, Angel P, Montoya JA, et al. The anti-inflammatory properties of halloysite. Applied Clay Science. 2012;**57**:10-16

[106] Caglar B. Structural characterization of kaolinitenicotinamide intercalation composite. Journal of Molecular Structure. 2012;**1020**:48-55

[107] Cervini-Silva J, Camacho AN, Kaufhold S, Ufer K, Jesús ER. The antiinflammatory activity of bentonites. Applied Clay Science. 2015;**118**:56-60

[108] Cervini-Silva J, Camacho AN, Palacios E, Angel P, Pentrak M, Pentrakova L, et al. Anti-inflammatory, antibacterial, and cytotoxic activity by natural matrices of nano-iron(hydr) oxide/halloysite. Applied Clay Science. 2016;**120**:101-110

[109] Awad ME, López-Galindo A, Setti M, El-Rahmany MM, Iborra CV. Kaolinite in pharmaceutics and biomedicine. International Journal of Pharmaceutics. 2017;**533**:34-48

[110] Tiwary AK, Poppenga RH, Puschner B. In vitro study of the effectiveness of three commercial adsorbents for binding oleander toxins. Clinical Toxicology. 2009;**47**:213-218

[111] Carraro A, De Giacomo A, Giannossi ML, Medici L, Muscarella M, Palazzo L, et al. Clay minerals as adsorbents of aflatoxin M1 from contaminated milk and effects on milk quality. Applied Clay Science. 2014;**88-89**:92-99

[112] Misyak SA, Burlaka AP, Golotiuk VV, Lukin SM, Kornienko PL. Antiradical, antimetastatic and antitumor activity of kaolin preparation Kremnevit. Galician Medical Journal. 2016;**23**(1):44-47

**123**

**Chapter 7**

**Abstract**

operation.

**1. Introduction**

concentrator plant will have [3–5].

Industry

Rheological Perspectives of

*Ricardo I. Jeldres and Matías Jeldres*

Clay-Based Tailings in the Mining

The mining industry faces a significant problem in regions with water scarcity and has had to put in place new strategies to preserve its environmental and economic sustainability. An attractive option in recent years has been the direct use of seawater, avoiding the construction of reverse osmosis plants to desalinate. But, some operational complexities are the subject of discussion and research for engineers; for example, the difficulties by the high presence of complex gangues like clays and the location of the plants, far from the coast and at high altitude. The latter requires high investments in pumping, the only option in some cases. In this scenario, it is imperative to improve the efficiency of water use and advance to effective closures of water circuits. A critical stage is the thickening that allows water to be recovered from the tailings, reusing it in upstream operations. However, the performance of the tailings management is usually limited by the rheological properties of the thickened slurries, which impact on the discharge from the underflow of the thickeners, pumping energy costs, disposal on the tailings storage facilities (TSFs). This text describes the consequences caused by a saline medium on the rheological properties of clay-based tailings, analysing scenarios that allow tackling this

**Keywords:** rheology, clays, seawater, thickening, tailings, water recovery

On a global scale, mining is a relatively small consumer of water compared to the agricultural or forestry industry, however, it can generate a significant social and environmental impact, mainly in those companies located in arid regions as occurs in numerous operations in Chile, Australia, and South Africa [1, 2]. The industry has made great efforts to optimise the use of water where the proper tailings management is crucial towards advance to the effective closure of water circuits. Essential aspects are the quantity and quality of water recovered in thickeners, solid concentration of the thickened slurries, drainage capacity of the underflow in the lower cone of thickeners, the energy and water required for transport, and the disposal strategies in the tailings storages facilities (TSFs). The rheological properties largely determine the performance of all the aspects previously mentioned and in many cases, it defines the success that the design of a

### **Chapter 7**

*Clay Science and Technology*

[102] López-Galindo A, Viseras C. Pharmaceutical and cosmetic applications of clays. In:

[103] Medzhitov R. Origin and physiological roles of inflammation.

Nature. 2008;**454**:428-435

2010;**109**:1221-1228

2012;**57**:10-16

2012;**1020**:48-55

2016;**120**:101-110

[105] Cornejo-Garrido H,

[106] Caglar B. Structural characterization of kaolinite-

Wypych F, Satyanarayana KG, editors. Clay Surfaces: Fundamentals and Applications. Amsterdam: Elsevier Academic Press; 2004. pp. 267-289

adsorbents for binding oleander toxins. Clinical Toxicology. 2009;**47**:213-218

Giannossi ML, Medici L, Muscarella M, Palazzo L, et al. Clay minerals as adsorbents of aflatoxin M1 from contaminated milk and effects on milk quality. Applied Clay Science.

[112] Misyak SA, Burlaka AP, Golotiuk VV, Lukin SM, Kornienko PL. Antiradical, antimetastatic and antitumor activity of kaolin preparation Kremnevit. Galician Medical Journal. 2016;**23**(1):44-47

[111] Carraro A, De Giacomo A,

2014;**88-89**:92-99

[104] Charkoudian N. Mechanisms and modifiers of reflex induced cutaneous vasodilation and vasoconstriction in humans. Journal of Applied Physiology.

Nieto-Camacho A, Gómez-Vidales V, Ramírez-Apan MT, Angel P, Montoya JA, et al. The anti-inflammatory properties of halloysite. Applied Clay Science.

nicotinamide intercalation composite. Journal of Molecular Structure.

[107] Cervini-Silva J, Camacho AN, Kaufhold S, Ufer K, Jesús ER. The antiinflammatory activity of bentonites. Applied Clay Science. 2015;**118**:56-60

[108] Cervini-Silva J, Camacho AN, Palacios E, Angel P, Pentrak M,

[109] Awad ME, López-Galindo A, Setti M, El-Rahmany MM, Iborra CV. Kaolinite in pharmaceutics and biomedicine. International Journal of Pharmaceutics. 2017;**533**:34-48

[110] Tiwary AK, Poppenga RH, Puschner B. In vitro study of the effectiveness of three commercial

Pentrakova L, et al. Anti-inflammatory, antibacterial, and cytotoxic activity by natural matrices of nano-iron(hydr) oxide/halloysite. Applied Clay Science.

**122**

## Rheological Perspectives of Clay-Based Tailings in the Mining Industry

*Ricardo I. Jeldres and Matías Jeldres*

### **Abstract**

The mining industry faces a significant problem in regions with water scarcity and has had to put in place new strategies to preserve its environmental and economic sustainability. An attractive option in recent years has been the direct use of seawater, avoiding the construction of reverse osmosis plants to desalinate. But, some operational complexities are the subject of discussion and research for engineers; for example, the difficulties by the high presence of complex gangues like clays and the location of the plants, far from the coast and at high altitude. The latter requires high investments in pumping, the only option in some cases. In this scenario, it is imperative to improve the efficiency of water use and advance to effective closures of water circuits. A critical stage is the thickening that allows water to be recovered from the tailings, reusing it in upstream operations. However, the performance of the tailings management is usually limited by the rheological properties of the thickened slurries, which impact on the discharge from the underflow of the thickeners, pumping energy costs, disposal on the tailings storage facilities (TSFs). This text describes the consequences caused by a saline medium on the rheological properties of clay-based tailings, analysing scenarios that allow tackling this operation.

**Keywords:** rheology, clays, seawater, thickening, tailings, water recovery

### **1. Introduction**

On a global scale, mining is a relatively small consumer of water compared to the agricultural or forestry industry, however, it can generate a significant social and environmental impact, mainly in those companies located in arid regions as occurs in numerous operations in Chile, Australia, and South Africa [1, 2]. The industry has made great efforts to optimise the use of water where the proper tailings management is crucial towards advance to the effective closure of water circuits. Essential aspects are the quantity and quality of water recovered in thickeners, solid concentration of the thickened slurries, drainage capacity of the underflow in the lower cone of thickeners, the energy and water required for transport, and the disposal strategies in the tailings storages facilities (TSFs). The rheological properties largely determine the performance of all the aspects previously mentioned and in many cases, it defines the success that the design of a concentrator plant will have [3–5].

### **2. Tailings management**

The different types of thickening technologies mostly establish the amount of water that can be extracted from the tailings, and hence the characteristics of the pulps that are transported to the TSFs. In the copper industry, conventional and high rate thickeners generate pulps between 50 and 60 wt% that have low yield stress (<40 Pa), while high-density and paste thickeners can make pulps over 65 wt% with yield stresses over 100 Pa [6, 7]. The thickened pulps are subsequently transported, usually by pumping to the tailings storage facilities (TSFs) [7].

The design of a tailings circuit should adequately consider the three stages involved (see **Figure 1**).


Among the most advanced technologies to promote tailings dewatering are paste thickeners (**Figure 2(a)**). These equipment have a much higher lateral height than the other types of thickeners, a higher inclination of the discharge cone (30-45%), and the product is a tailing with a maximum concentration of solids. The pulps can

**125**

*Rheological Perspectives of Clay-Based Tailings in the Mining Industry*

reach solids concentrations near to 70 wt%, maximising the tailings dewatering, and facilitating their disposal in the TSFs (**Figure 2(b)**). Here comes the importance of the rheological properties of the slurries, since their pumping could incur

The traditional method to characterise the rheological behaviour of tailings is through flow curves that are fitted to viscoplastic models such as Bingham or Herschel-Bulkley. Then, the yield stress is derived, which is widely used to describe, design, and control tailings processes in pipelines and beds. The accuracy of such measurements is controversial, and great care must be taken in some systems where precise equilibrium data is challenging to obtain (that is common for mining tailings). Nguyen and Boger [8] adopted the static yield stress vane measurement that is simple and has become widely used. Fisher et al. [9] later concluded that while the rough surfaces of the cup and bob geometries can be used successfully, infinite cup vane geometry alleviates all wall effects and it is a suitable method of determining yield stress and flow at steady-state behaviour of strongly aggregated particle

Reograms are graphical representations of the response of the shear stress to variations in the angular strain rate, considering a material (suspension, in this case) between two parallel planes where one is moved, and the other remains immobile. The resolution of the Navier-Stokes equations, which describe the movement of the fluid, is simplified to an analytical form, taking care that the inertial forces are small compared to the viscous forces. Consequently, the viscometric flow is characterised by simple configurations in which the only relevant component of the stress tensor is the pure shear. Therefore the inverse problem for the viscosity can be solved directly by fitting the experimental measurements of some physical

For the accurate description of the empirically obtained rheograms, it is necessary to consider the boundary conditions that are used to solve the Navier-Stokes equations in their simplified form. This means that particle sedimentation, the appearance of secondary flows (e.g. Taylor vortices) and phenomena such as wall

*DOI: http://dx.doi.org/10.5772/intechopen.93813*

excessive energy costs.

**Figure 2.**

suspensions.

magnitude, as the torque M.

slip should be avoided.

**3. Rheological characterisation**

*(a) Paste thickener, (b) depositing of a tailing from a paste thickener.*

### **Figure 1.**

*Schematic representation of the stages involved in tailings management.*

*Rheological Perspectives of Clay-Based Tailings in the Mining Industry DOI: http://dx.doi.org/10.5772/intechopen.93813*

*Clay Science and Technology*

involved (see **Figure 1**).

mainly);

advantages;

thickening technologies.

*Schematic representation of the stages involved in tailings management.*

**2. Tailings management**

The different types of thickening technologies mostly establish the amount of water that can be extracted from the tailings, and hence the characteristics of the pulps that are transported to the TSFs. In the copper industry, conventional and high rate thickeners generate pulps between 50 and 60 wt% that have low yield stress (<40 Pa), while high-density and paste thickeners can make pulps over 65 wt% with yield stresses over 100 Pa [6, 7]. The thickened pulps are subsequently

i.Performance in water recovery in solid-liquid separation stages (thickening

ii.Pumping of thickened tailings, whose costs fluctuate depending on the characteristics of both the pulps (rheological properties) and geography of the plants. In some instances the thickeners are located at a higher altitude than the TSFs, and gravity might assist the pumping. In contrast, on other cases the cost per transport may be decisive, especially when the distances are too long, the tailings have high density, or there are no gravitational

iii.Disposal methods and dewatering in TSFs, which primarily depend on the rheological behaviour of the slurries that consequently are a result of the

Among the most advanced technologies to promote tailings dewatering are paste thickeners (**Figure 2(a)**). These equipment have a much higher lateral height than the other types of thickeners, a higher inclination of the discharge cone (30-45%), and the product is a tailing with a maximum concentration of solids. The pulps can

transported, usually by pumping to the tailings storage facilities (TSFs) [7]. The design of a tailings circuit should adequately consider the three stages

**124**

**Figure 1.**

**Figure 2.** *(a) Paste thickener, (b) depositing of a tailing from a paste thickener.*

reach solids concentrations near to 70 wt%, maximising the tailings dewatering, and facilitating their disposal in the TSFs (**Figure 2(b)**). Here comes the importance of the rheological properties of the slurries, since their pumping could incur excessive energy costs.

### **3. Rheological characterisation**

The traditional method to characterise the rheological behaviour of tailings is through flow curves that are fitted to viscoplastic models such as Bingham or Herschel-Bulkley. Then, the yield stress is derived, which is widely used to describe, design, and control tailings processes in pipelines and beds. The accuracy of such measurements is controversial, and great care must be taken in some systems where precise equilibrium data is challenging to obtain (that is common for mining tailings). Nguyen and Boger [8] adopted the static yield stress vane measurement that is simple and has become widely used. Fisher et al. [9] later concluded that while the rough surfaces of the cup and bob geometries can be used successfully, infinite cup vane geometry alleviates all wall effects and it is a suitable method of determining yield stress and flow at steady-state behaviour of strongly aggregated particle suspensions.

Reograms are graphical representations of the response of the shear stress to variations in the angular strain rate, considering a material (suspension, in this case) between two parallel planes where one is moved, and the other remains immobile. The resolution of the Navier-Stokes equations, which describe the movement of the fluid, is simplified to an analytical form, taking care that the inertial forces are small compared to the viscous forces. Consequently, the viscometric flow is characterised by simple configurations in which the only relevant component of the stress tensor is the pure shear. Therefore the inverse problem for the viscosity can be solved directly by fitting the experimental measurements of some physical magnitude, as the torque M.

For the accurate description of the empirically obtained rheograms, it is necessary to consider the boundary conditions that are used to solve the Navier-Stokes equations in their simplified form. This means that particle sedimentation, the appearance of secondary flows (e.g. Taylor vortices) and phenomena such as wall slip should be avoided.

**Figure 3.**

*Representation of Taylor vortices in a Couette geometry.*

### **3.1 Taylor's vortices**

Some low-viscosity slurries may involve a secondary flow driven by the inertia of the sample, forming a phenomenon called Taylor vortices (see **Figure 3**). When this happens, it is common for rheograms to observe a false increase in rheological properties or even shear thickening (dilatant) behaviours.

The appearance of the vortices is anticipated by the Taylor number (*T*), which in the case of concentric cylinders with internal cylinder rotation is described by the Eq. (1):

$$T = 2 \cdot \left(\frac{a\_\text{\\_}}{a\_\text{\\_}}\right)^2 \cdot \left(\frac{\left(a\_\text{\\_} - a\_\text{\\_}\right)^4}{\text{1} - \left(\frac{a\_\text{\\_}}{a\_\text{\\_}}\right)^2}\right) \cdot \left(\frac{\rho \cdot \alpha}{\eta}\right)^2\tag{1}$$

Where:


### **3.2 Wall-slip**

The obtaining of rheological parameters is based on the Navier-Stokes equation, whose expression is given by the Eq. (2):

$$\left[\eta \left(\frac{\partial}{\partial r} \left(\frac{\mathbf{1}}{r} \frac{\partial}{\partial r} (r\nu\_{\boldsymbol{\theta}})\right)\right)\right] = \mathbf{0} \tag{2}$$

**127**

**Figure 4.**

*Prud'homme [10]).*

*Rheological Perspectives of Clay-Based Tailings in the Mining Industry*

made with geometries of different dimensions and shapes.

*us*

) <sup>∗</sup> , slip velocity at the cup or bob surface

, cup/bob ratio 0 / = *R R <sup>i</sup>*

• Ù, angular velocity

τ

∗

the slip velocity which corresponds to the stress

of the inner and outer cups. However, it is common for a wall slip phenomenon to occur, which is defined as the difference between the speeds of the wall relative to

This phenomenon is caused by a thin layer of solution that forms on the walls and creates a wrong decrease in rheological properties. Obtaining the right rheological behaviour needs performing a rheogram correction, based on measurements

A method proposed by Yoshimura and Prud'homme [10], expects only two measurements, using geometries with different gaps but with the same ratio between the radii of the cup and the internal cylinder. According to this method,

( ) 1 2

**Figure 4** shows the typical result of preparing measurements with different Ù ranges on each device. Yoshimura and Prud'homme [10] validated the proposed method with 1.9 wt% clay suspensions, measuring on different Couette devices. **Figure 4** also shows the experimental measurements and the corrected rheo-

Commonly, concentrated tailings show a non-Newtonian behaviour where they have an elastic limit. The yield stress, τy, is the critical shear stress that must be overcome before irreversible deformation and flow can occur. The yield stress is an engineering reality, although the rheology community debates hard about its

*Angular velocity (Ω) vs. bob stress for a 1.9 wt% clay suspension measured on different Couette devices. Also shown is the angular velocity corrected for wall slip (Ωf) vs. bob stress (adapted from Yoshimura and* 

κ

κ

τ

1 2

*R R*

<sup>+</sup> <sup>−</sup>

Ù Ù 1 1 1

<sup>−</sup> <sup>=</sup>

<sup>∗</sup> from two angular velocity can be

(3)

*DOI: http://dx.doi.org/10.5772/intechopen.93813*

that of the fluid in the wall.

described as:

Where:

• *us*(τ

gram value.

• κ

Obtaining an analytical solution to the expression requires a series of assumptions, for example, that the fluid moves in laminar flow, with streamlines moving in a radial direction, around the inner cylinder as shown in **Figure 3**. In particular, the fluid layer located in the contours is assumed to move at the same speed as the walls

*Rheological Perspectives of Clay-Based Tailings in the Mining Industry DOI: http://dx.doi.org/10.5772/intechopen.93813*

of the inner and outer cups. However, it is common for a wall slip phenomenon to occur, which is defined as the difference between the speeds of the wall relative to that of the fluid in the wall.

This phenomenon is caused by a thin layer of solution that forms on the walls and creates a wrong decrease in rheological properties. Obtaining the right rheological behaviour needs performing a rheogram correction, based on measurements made with geometries of different dimensions and shapes.

A method proposed by Yoshimura and Prud'homme [10], expects only two measurements, using geometries with different gaps but with the same ratio between the radii of the cup and the internal cylinder. According to this method, the slip velocity which corresponds to the stress τ <sup>∗</sup> from two angular velocity can be described as:

$$
\mu\_s \left( \tau^\* \right) = \frac{\kappa}{\kappa + \mathbf{1}} \left[ \frac{\mathbf{\hat{U}}\_\text{\tiny\kern-1.5mu\text{R}} - \mathbf{\hat{U}}\_\text{\tiny\kern-1.5mu\text{R}}}{\mathbf{\frac{\mathbf{1}}{\left[ \begin{array}{c} \mathbf{1} \\ R\_\text{\tiny\kern-1.5mu\text{R}} \end{array} \right]}} \right]\_\text{\tiny\kern-1.5mu\text{R}} \tag{3}
$$

Where:

*Clay Science and Technology*

**3.1 Taylor's vortices**

*Representation of Taylor vortices in a Couette geometry.*

the Eq. (1):

**Figure 3.**

Where:

• ρ

• ω

• η

**3.2 Wall-slip**

• *a*1 inner radius • *a*2 outer radius

liquid density

fluid viscosity

whose expression is given by the Eq. (2):

Some low-viscosity slurries may involve a secondary flow driven by the inertia of the sample, forming a phenomenon called Taylor vortices (see **Figure 3**). When this happens, it is common for rheograms to observe a false increase in rheological

The appearance of the vortices is anticipated by the Taylor number (*T*), which in the case of concentric cylinders with internal cylinder rotation is described by

1 2 1

*a a a*

<sup>2</sup> <sup>1</sup>

*a a*

1

( ) <sup>2</sup> <sup>4</sup> <sup>2</sup>

2

ρ ω

η

(1)

2

*a*

The obtaining of rheological parameters is based on the Navier-Stokes equation,

( ) <sup>1</sup>

Obtaining an analytical solution to the expression requires a series of assumptions, for example, that the fluid moves in laminar flow, with streamlines moving in a radial direction, around the inner cylinder as shown in **Figure 3**. In particular, the fluid layer located in the contours is assumed to move at the same speed as the walls

 ∂ ∂ =

 υθ

*rrr*

*r* 0

∂ ∂ (2)

<sup>−</sup> <sup>⋅</sup> =⋅ ⋅ ⋅ <sup>−</sup>

properties or even shear thickening (dilatant) behaviours.

2

rotational speed of the inner cylinder in rad/s

η

*T*

**126**


**Figure 4** shows the typical result of preparing measurements with different Ù ranges on each device. Yoshimura and Prud'homme [10] validated the proposed method with 1.9 wt% clay suspensions, measuring on different Couette devices. **Figure 4** also shows the experimental measurements and the corrected rheogram value.

Commonly, concentrated tailings show a non-Newtonian behaviour where they have an elastic limit. The yield stress, τy, is the critical shear stress that must be overcome before irreversible deformation and flow can occur. The yield stress is an engineering reality, although the rheology community debates hard about its

### **Figure 4.**

*Angular velocity (Ω) vs. bob stress for a 1.9 wt% clay suspension measured on different Couette devices. Also shown is the angular velocity corrected for wall slip (Ωf) vs. bob stress (adapted from Yoshimura and Prud'homme [10]).*

real existence [11, 12]. The truth is that its estimation is a routine practice to define control strategies for the management of mine tailings [13–15].

Yield stress depends on chemical interactions between particles, size distribution, and pulp density. This last aspect is critical in the search to maximise water recovery; however, the relationship between density and yield stress follows an exponential law where small changes in the percentage of solids lead to a significant rise in the value of yield stress. A schematic representation of the implications of thickening technology on the density and rheological behaviour of the pulps is shown in **Figure 5**. For example, when the underflow is thickened to too high concentration, the energy cost per pumping can reach prohibitive values, and operators may be required to dilute the thickened tailings, which means sacrificing water that could have been recirculated to upstream operations.

In the last time, some studies have integrated additional parameters in the discussion, especially analysing the viscoelastic behaviour of the pulps. Although to date there are no publications that directly use of viscoelastic parameters for the design of tailings circuits, their knowledge has allowed obtaining more information on the strength of the particle networks that make up the mineral slurries [16–18]. The behaviour of the sample is described through a viscous component, represented by the storage modulus (*G′*), and an elastic part, represented by the loss modulus (*G″*) [19]. The viscoelastic modulus can be obtained using dynamic oscillatory rheology methods, which are carried out by subjecting the sample to an oscillatory deformation γγω (*t t* ) = <sup>0</sup> sin( ) , obtaining the resulting stress as a function of time τγ ωω ωω(*t G tG t* ) = <sup>0</sup> ( ′( )sin( ) + ″( )cos( )) . *G′* is a measure of the material's stored

energy and is therefore related to molecular events of an elastic nature, while *G″* indicates the energy dissipated as heat, associated with viscous molecular events.

Lin et al. [18] analysed the structural changes of kaolinite particle junctions concerning the pH and concentration of solids in the pulp. Using small-amplitude oscillatory shear (SAOS) tests, the authors concluded that the gelation by attractive interactions in low-mass fractions changes to gelation by face-to-face interactions by increasing the particle mass fraction. Gelation by face-to-face interactions is stabilised by the repulsive electrostatic force between the faces of the disk-shaped particles. Based on a DLVO theory that is based on attractive forces between

**129**

**Figure 6.**

*the quartz surface (adapted from Jeldres et al. [27]).*

K+

sizes, following the order Li+

*Rheological Perspectives of Clay-Based Tailings in the Mining Industry*

**4. Rheological behaviour in saline environments**

properties of a quartz suspension to be reduced [26].

particles, a modified model has been developed based on the repulsive electrostatic

The current tailings dewatering challenges within the mining industry are the upstream use of low-quality water (like seawater) in processing and complex gangues like clays [20–22]. In the first case, the behaviour of the pulps in a highly saline environment must be faced, which is complex from a scientific point of view, since salinity significantly alters the interactions between the particle's surfaces, bringing important consequences in the rheological properties. They are strongly related to salinity and the type of salt [23]. For example, Reyes et al. [24] studied the rheological behaviour of magnetite tailings without flocculation, using mixtures of freshwater with seawater in different proportions. The authors were able to explain their findings in terms of electrostatic interactions, since they related the value of yield stress with the magnitude of the zeta potential, following the recommendation proposed two decades ago by Johnson et al. [25]. However, it should be noted that in complex saline systems, like seawater, there are many ions of different nature interacting simultaneously. In this case, the divalent cation speciation and the maker/breaker type may have an important role. For example, the formation of solid magnesium complexes at high pH (pH < 10.5) can cause the rheological

Jeldres et al. [27] analysed the viscoelastic behaviour of quartz suspensions prepared in monovalent brines. As seen in **Figure 6(a)**, there is a direct relationship between the size of the cations and the yield stress. The authors explained that silica has a more significant trend to agglomerate in the presence of larger ions like

According to fundamental studies, the surface of the silica would present a breakerlike behaviour [28], having a higher affinity with species of the same nature as is observed in **Figure 6(b)**, where the amount of adsorbed cation increases for larger

have a higher affinity for water molecules, exhibiting a maker-like behaviour [29]. Clays are a consistent focus of research because they negatively impact almost all processes in the mining sector, including leaching, flotation, pulp transport, thickening, etc. [16, 30, 31]. These phyllosilicates can be classified according to their swelling (e.g. sodium montmorillonite) and non-swelling (e.g. kaolinite) character. This classification is made according to the response of the particles when they come into contact with water, being able to preserve their structure or increase their

*Effect of the type of salt on (a) yield stress of quartz suspensions; (b) adsorption of the monovalent cation on* 

 and Li+ .

. In the case of clays, the surface would

, forming stronger particle networks compared to smaller salts like Na+

< Cs+

< Na+

*DOI: http://dx.doi.org/10.5772/intechopen.93813*

force between the faces of the platelets.

### **Figure 5.**

*Relationship between the type of thickener and properties of the underflows (solid concentration and yield stress).*

*Clay Science and Technology*

deformation

 ωω

τγ

real existence [11, 12]. The truth is that its estimation is a routine practice to define

Yield stress depends on chemical interactions between particles, size distribution, and pulp density. This last aspect is critical in the search to maximise water recovery; however, the relationship between density and yield stress follows an exponential law where small changes in the percentage of solids lead to a significant rise in the value of yield stress. A schematic representation of the implications of thickening technology on the density and rheological behaviour of the pulps is shown in **Figure 5**. For example, when the underflow is thickened to too high concentration, the energy cost per pumping can reach prohibitive values, and operators may be required to dilute the thickened tailings, which means sacrificing water that

In the last time, some studies have integrated additional parameters in the discussion, especially analysing the viscoelastic behaviour of the pulps. Although to date there are no publications that directly use of viscoelastic parameters for the design of tailings circuits, their knowledge has allowed obtaining more information on the strength of the particle networks that make up the mineral slurries [16–18]. The behaviour of the sample is described through a viscous component, represented by the storage modulus (*G′*), and an elastic part, represented by the loss modulus (*G″*) [19]. The viscoelastic modulus can be obtained using dynamic oscillatory rheology methods, which are carried out by subjecting the sample to an oscillatory

 (*t G tG t* ) = <sup>0</sup> ( ′( )sin( ) + ″( )cos( )) . *G′* is a measure of the material's stored energy and is therefore related to molecular events of an elastic nature, while *G″* indicates the energy dissipated as heat, associated with viscous molecular events. Lin et al. [18] analysed the structural changes of kaolinite particle junctions concerning the pH and concentration of solids in the pulp. Using small-amplitude oscillatory shear (SAOS) tests, the authors concluded that the gelation by attractive interactions in low-mass fractions changes to gelation by face-to-face interactions by increasing the particle mass fraction. Gelation by face-to-face interactions is stabilised by the repulsive electrostatic force between the faces of the disk-shaped particles. Based on a DLVO theory that is based on attractive forces between

*Relationship between the type of thickener and properties of the underflows (solid concentration and yield* 

(*t t* ) = <sup>0</sup> sin( ) , obtaining the resulting stress as a function of time

control strategies for the management of mine tailings [13–15].

could have been recirculated to upstream operations.

 ωω

γγω

**128**

**Figure 5.**

*stress).*

particles, a modified model has been developed based on the repulsive electrostatic force between the faces of the platelets.

### **4. Rheological behaviour in saline environments**

The current tailings dewatering challenges within the mining industry are the upstream use of low-quality water (like seawater) in processing and complex gangues like clays [20–22]. In the first case, the behaviour of the pulps in a highly saline environment must be faced, which is complex from a scientific point of view, since salinity significantly alters the interactions between the particle's surfaces, bringing important consequences in the rheological properties. They are strongly related to salinity and the type of salt [23]. For example, Reyes et al. [24] studied the rheological behaviour of magnetite tailings without flocculation, using mixtures of freshwater with seawater in different proportions. The authors were able to explain their findings in terms of electrostatic interactions, since they related the value of yield stress with the magnitude of the zeta potential, following the recommendation proposed two decades ago by Johnson et al. [25]. However, it should be noted that in complex saline systems, like seawater, there are many ions of different nature interacting simultaneously. In this case, the divalent cation speciation and the maker/breaker type may have an important role. For example, the formation of solid magnesium complexes at high pH (pH < 10.5) can cause the rheological properties of a quartz suspension to be reduced [26].

Jeldres et al. [27] analysed the viscoelastic behaviour of quartz suspensions prepared in monovalent brines. As seen in **Figure 6(a)**, there is a direct relationship between the size of the cations and the yield stress. The authors explained that silica has a more significant trend to agglomerate in the presence of larger ions like K+ , forming stronger particle networks compared to smaller salts like Na+ and Li+ . According to fundamental studies, the surface of the silica would present a breakerlike behaviour [28], having a higher affinity with species of the same nature as is observed in **Figure 6(b)**, where the amount of adsorbed cation increases for larger sizes, following the order Li+ < Na+ < Cs+ . In the case of clays, the surface would have a higher affinity for water molecules, exhibiting a maker-like behaviour [29].

Clays are a consistent focus of research because they negatively impact almost all processes in the mining sector, including leaching, flotation, pulp transport, thickening, etc. [16, 30, 31]. These phyllosilicates can be classified according to their swelling (e.g. sodium montmorillonite) and non-swelling (e.g. kaolinite) character. This classification is made according to the response of the particles when they come into contact with water, being able to preserve their structure or increase their

**Figure 6.**

*Effect of the type of salt on (a) yield stress of quartz suspensions; (b) adsorption of the monovalent cation on the quartz surface (adapted from Jeldres et al. [27]).*

apparent volume in solution. Kaolinite (Al2Si2O5(OH)4) (**Figure 7**) is composed of an octahedral sheet of aluminium hydroxide and a tetrahedral sheet of silica which are joined to form a basic 1:1 repeating unit. This clay has two crystallographically different surfaces: the faces that are negatively charged, and the edges, which vary their charge (anionic or cationic) depending on the pH that arises from the protonation or deprotonation of the aluminium (Al▬OH) and silanol groups (Si▬OH) in the exposed planes with hydroxyl termination. Due to their anisotropic structure and charge properties, clay sheets can form different types of interactions: face-toface (FF), edge-to-edge (EE) and edge-to-face (EF).

Montmorillonite (**Figure 8**) is composed of an octahedral alumina sheet and two tetrahedral silica sheets that join to form a basic unit of repeating layers in a 2:1 ratio [32]. The central layer contains octahedral coordinated Al and Mg in the form of oxides and hydroxides and is surrounded by two external layers formed by tetrahedral coordinated silicon oxides. This clay has high chemical stability, a large surface

### **Figure 7.**

*Representation of the kaolinite structure. The green sheet indicates the tetrahedral layer of silicon (T) and the yellow sheet corresponds to the octahedral layer of alumina (O).*

### **Figure 8.**

*Representation of the sodium montmorillonite structure. The green sheet indicates the tetrahedral layer of silicon (T) and the yellow sheet corresponds to the octahedral layer of alumina (O).*

**131**

**Figure 9.**

*Au and Leong [40]).*

*Rheological Perspectives of Clay-Based Tailings in the Mining Industry*

nature of the water and the presence of ions in solution [39].

area and a top ion exchange capacity as a result of its weakly bound octahedral sheets. Unlike kaolinite, montmorillonite has a high capacity to swell in the presence of freshwater as a result of water molecules entering the middle of the layers [33]. In freshwater, the swelling effect of montmorillonite is more significant than in saline medium. This is because the cations being in saline water helps to neutralise the negative charges of the interlayer layers of the clay, reducing its electrostatic repulsion and therefore its separation distance [34–36]. This prevents the entrance of water molecules into the clay, notably impacting its swelling [37]. The high level of particles' swelling in freshwater implies an increase in the apparent volume concentration, which generates a considerable increase in the rheological properties of the slurries [38]. However, this characteristic is strongly influenced by the chemical

The chemical differences in the surface cause significant changes in the rheological properties of the pulps. For this reason, clay suspensions are exposed to dramatic changes concerning the pH of the suspension, mainly due to changes in electrostatic forces on surfaces. At low pH, there are anionic (faces) and cationic (edges) zones that generate attractive strong bonds between the particles, which clump together to form a "house of cards" structure. However, increasing the pH intensifies a greater electrostatic repulsion, causing the particles to disperse and the suspension to be more stable. The rheological consequences regarding pH have been widely addressed in the literature. Clays of 1:1 structure such as kaolinite generally show a behaviour that is decreasing concerning pH (**Figure 9**). In contrast, swelling clays such as montmorillonite have demonstrated the marked presence of a maxi-

The electrostatic attraction between the faces and edges is the primary mechanism that gives strength to the bonds between clay particles. For this reason, the presence of salt causes a reduction in electrical charges, resulting in lower viscosity and yield stress. **Figure 11** shows the impact of adding 0.1 M of electrolytes to the suspension. The rheogram curve shifts downwards when salt is present, however, the values strongly depends on the type of cation, where divalent cations generate a greater impact as they are more efficient in compressing the double electrical layer. The effect at alkaline conditions is different. The slurries in freshwater have low rheological parameters but the compression of the double-layer may favour the particles' aggregation, forming both hydrogen and cationic bonds. The result is that the rheological properties increase in a saline medium like seawater; therefore, the management of clay-based tailings may involve higher energy costs. In this sense, it

*Relationship between pH and yield stress for crown kaolin slurries at varied solid concentration (adapted from* 

*DOI: http://dx.doi.org/10.5772/intechopen.93813*

mum at pH around 4 (**Figure 10**).

### *Rheological Perspectives of Clay-Based Tailings in the Mining Industry DOI: http://dx.doi.org/10.5772/intechopen.93813*

*Clay Science and Technology*

apparent volume in solution. Kaolinite (Al2Si2O5(OH)4) (**Figure 7**) is composed of an octahedral sheet of aluminium hydroxide and a tetrahedral sheet of silica which are joined to form a basic 1:1 repeating unit. This clay has two crystallographically different surfaces: the faces that are negatively charged, and the edges, which vary their charge (anionic or cationic) depending on the pH that arises from the protonation or deprotonation of the aluminium (Al▬OH) and silanol groups (Si▬OH) in the exposed planes with hydroxyl termination. Due to their anisotropic structure and charge properties, clay sheets can form different types of interactions: face-to-

Montmorillonite (**Figure 8**) is composed of an octahedral alumina sheet and two tetrahedral silica sheets that join to form a basic unit of repeating layers in a 2:1 ratio [32]. The central layer contains octahedral coordinated Al and Mg in the form of oxides and hydroxides and is surrounded by two external layers formed by tetrahedral coordinated silicon oxides. This clay has high chemical stability, a large surface

*Representation of the kaolinite structure. The green sheet indicates the tetrahedral layer of silicon (T) and the* 

*Representation of the sodium montmorillonite structure. The green sheet indicates the tetrahedral layer of* 

*silicon (T) and the yellow sheet corresponds to the octahedral layer of alumina (O).*

face (FF), edge-to-edge (EE) and edge-to-face (EF).

*yellow sheet corresponds to the octahedral layer of alumina (O).*

**130**

**Figure 8.**

**Figure 7.**

area and a top ion exchange capacity as a result of its weakly bound octahedral sheets. Unlike kaolinite, montmorillonite has a high capacity to swell in the presence of freshwater as a result of water molecules entering the middle of the layers [33]. In freshwater, the swelling effect of montmorillonite is more significant than in saline medium. This is because the cations being in saline water helps to neutralise the negative charges of the interlayer layers of the clay, reducing its electrostatic repulsion and therefore its separation distance [34–36]. This prevents the entrance of water molecules into the clay, notably impacting its swelling [37]. The high level of particles' swelling in freshwater implies an increase in the apparent volume concentration, which generates a considerable increase in the rheological properties of the slurries [38]. However, this characteristic is strongly influenced by the chemical nature of the water and the presence of ions in solution [39].

The chemical differences in the surface cause significant changes in the rheological properties of the pulps. For this reason, clay suspensions are exposed to dramatic changes concerning the pH of the suspension, mainly due to changes in electrostatic forces on surfaces. At low pH, there are anionic (faces) and cationic (edges) zones that generate attractive strong bonds between the particles, which clump together to form a "house of cards" structure. However, increasing the pH intensifies a greater electrostatic repulsion, causing the particles to disperse and the suspension to be more stable. The rheological consequences regarding pH have been widely addressed in the literature. Clays of 1:1 structure such as kaolinite generally show a behaviour that is decreasing concerning pH (**Figure 9**). In contrast, swelling clays such as montmorillonite have demonstrated the marked presence of a maximum at pH around 4 (**Figure 10**).

The electrostatic attraction between the faces and edges is the primary mechanism that gives strength to the bonds between clay particles. For this reason, the presence of salt causes a reduction in electrical charges, resulting in lower viscosity and yield stress. **Figure 11** shows the impact of adding 0.1 M of electrolytes to the suspension. The rheogram curve shifts downwards when salt is present, however, the values strongly depends on the type of cation, where divalent cations generate a greater impact as they are more efficient in compressing the double electrical layer. The effect at alkaline conditions is different. The slurries in freshwater have low rheological parameters but the compression of the double-layer may favour the particles' aggregation, forming both hydrogen and cationic bonds. The result is that the rheological properties increase in a saline medium like seawater; therefore, the management of clay-based tailings may involve higher energy costs. In this sense, it

### **Figure 9.**

*Relationship between pH and yield stress for crown kaolin slurries at varied solid concentration (adapted from Au and Leong [40]).*

### **Figure 10.**

*Relationship between pH and yield stress for Na-montmorillonite slurries at varied solid concentration (adapted from Au and Leong [40]).*

### **Figure 11.**

*Comparison between the effects of monovalent and divalent electrolytes on the flow curves of bentonite 1. Suspension: 8% bentonite in 0.1 M electrolyte solution (adapted from Abu-Jdayil [41]).*

is necessary to find strategies to obtain pulps with rheological properties that simplify their transport. Contreras et al. [38] studied the effect of NaCl concentration on the rheological properties of synthetic tailings composed of mixtures of quartz and clays. Considering that the pulps were prepared at natural pH, it was found that salinity lowered the yield stress, as shown in **Figure 12**.

### **5. Chemical reagents**

The permanent challenge for tailings management is to be able to manipulate their rheological properties, according to the plant bases. When seeking to facilitate the discharge of the tailings from the thickeners and to reduce the water and energy consumption involved in their transport by pumping, it is needed to find methods to reduce the values of yield stress and viscosity. Li et al. [42] used polycarboxylate copolymers synthesised in the treatment of kaolin suspensions. The results revealed the high capacity of the polymers to reduce the viscosity, due to the dispersion of the particles caused by steric and electrostatic effects, by increasing the anionic charge of the particles.

Du et al. [43] enlarged the electrostatic repulsion between bentonite particles by adding multiple charged phosphate-based reagents. The authors could reduce the

**133**

**Figure 13.**

**Figure 12.**

*Rheological Perspectives of Clay-Based Tailings in the Mining Industry*

yield stress to zero when it was a tetravalent or higher valence (see **Figure 13**). The results were explained by the changes in the electrostatic interactions, where the salts with higher valence were more pragmatic in reducing the negative zeta

However, when interactions occur in a highly saline medium, such as seawater, it is challenging to suggest strategies that drive an electrostatic repulsion since the high concentration of counter ions reduces the electrical double layer, making electrostatic changes less significant. For this reason, Robles et al. [44] recommended that the most efficient reagents are those that cause steric stabilisation of the

*Effect of the salinity on the yield stress of clay suspensions: (a) pure kaolin; (b) kaolin/Na-bentonite, 50/50;* 

*Effect of phosphate-based additives on the yield stress of bentonite slurries (adapted from Du et al. [43]).*

*(c) pure Na-bentonite (adapted from Contreras et al. [38]).*

*DOI: http://dx.doi.org/10.5772/intechopen.93813*

potential (**Table 1**).

*Rheological Perspectives of Clay-Based Tailings in the Mining Industry DOI: http://dx.doi.org/10.5772/intechopen.93813*

yield stress to zero when it was a tetravalent or higher valence (see **Figure 13**). The results were explained by the changes in the electrostatic interactions, where the salts with higher valence were more pragmatic in reducing the negative zeta potential (**Table 1**).

However, when interactions occur in a highly saline medium, such as seawater, it is challenging to suggest strategies that drive an electrostatic repulsion since the high concentration of counter ions reduces the electrical double layer, making electrostatic changes less significant. For this reason, Robles et al. [44] recommended that the most efficient reagents are those that cause steric stabilisation of the

### **Figure 12.**

*Clay Science and Technology*

**Figure 10.**

**Figure 11.**

*(adapted from Au and Leong [40]).*

is necessary to find strategies to obtain pulps with rheological properties that simplify their transport. Contreras et al. [38] studied the effect of NaCl concentration on the rheological properties of synthetic tailings composed of mixtures of quartz and clays. Considering that the pulps were prepared at natural pH, it was found that

*Comparison between the effects of monovalent and divalent electrolytes on the flow curves of bentonite 1.* 

*Suspension: 8% bentonite in 0.1 M electrolyte solution (adapted from Abu-Jdayil [41]).*

*Relationship between pH and yield stress for Na-montmorillonite slurries at varied solid concentration* 

The permanent challenge for tailings management is to be able to manipulate their rheological properties, according to the plant bases. When seeking to facilitate the discharge of the tailings from the thickeners and to reduce the water and energy consumption involved in their transport by pumping, it is needed to find methods to reduce the values of yield stress and viscosity. Li et al. [42] used polycarboxylate copolymers synthesised in the treatment of kaolin suspensions. The results revealed the high capacity of the polymers to reduce the viscosity, due to the dispersion of the particles caused by steric and electrostatic effects, by increasing the anionic charge of the particles.

Du et al. [43] enlarged the electrostatic repulsion between bentonite particles by adding multiple charged phosphate-based reagents. The authors could reduce the

salinity lowered the yield stress, as shown in **Figure 12**.

**5. Chemical reagents**

**132**

*Effect of the salinity on the yield stress of clay suspensions: (a) pure kaolin; (b) kaolin/Na-bentonite, 50/50; (c) pure Na-bentonite (adapted from Contreras et al. [38]).*

**Figure 13.** *Effect of phosphate-based additives on the yield stress of bentonite slurries (adapted from Du et al. [43]).*


**Table 1.**

*The effect of 10 dwb% phosphate-based additives on the zeta potential and pH of 7 wt% bentonite slurries (adapted from Du et al. [43]).*

### **Figure 14.**

*Herschel-Bulkley parameters (yield stress and flow index) of kaolin pulp in seawater at pH 8 with varied sodium polyacrylate concentrations (Robles et al. [44]).*

particles. The authors studied the influence of sodium polyacrylate of low molecular weight on the performance and viscoelasticity of kaolin pulps in seawater. It was shown that the reagent could reduce the strength of the bonds between the particles through steric stabilisation, considerably lowering the yield stress (**Figure 14**).

It was interesting that this polymer of low molecular weight provides promising results in a highly saline medium since the main reports in the literature have given its efficiency to the induction of higher anionic charges on the surfaces [45, 46].

### **6. Outlook**

Tailings management in saline environments continues to be a challenging issue for plant design and operation, especially when significant clay content appears. Numerous factors enter the discussion, such as water quality, mineralogy (the type of clay), legal regulations, availability of water resources, etc. The need to improve the efficiency of this operation has increased in recent years, which has attracted greater scientific interest. Notable improvements have emerged from a technological point of view, in which the market offers increasingly robust equipment. That allows significant amounts of water to be extracted from the tailings and recycle them to upstream operations, with economic, environmental, and social benefits considering that many industries compete with neighbouring communities for disposing of the water resource. So reducing the water make-up means that more water would be available to the population.

### **Acknowledgements**

The authors thank ANID/Fondecyt/11171036 and Centro CRHIAM Project ANID/FONDAP/15130015.

**135**

Chile

**Author details**

Ricardo I. Jeldres1

Antofagasta, Antofagasta, Chile

provided the original work is properly cited.

\* and Matías Jeldres2

\*Address all correspondence to: ricardo.jeldres@uantof.cl

1 Department of Chemical Engineering and Mineral Processing, University of

2 Faculty of Engineering and Architecture, Arturo Prat University, Antofagasta,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Rheological Perspectives of Clay-Based Tailings in the Mining Industry*

*DOI: http://dx.doi.org/10.5772/intechopen.93813*

The authors declare no conflict of interest.

**Conflict of interest**

*Rheological Perspectives of Clay-Based Tailings in the Mining Industry DOI: http://dx.doi.org/10.5772/intechopen.93813*

### **Conflict of interest**

*Clay Science and Technology*

*(adapted from Du et al. [43]).*

**None** <sup>3</sup> *PO*<sup>4</sup>

<sup>−</sup> <sup>3</sup> *P O*3 9

Ζ (mV) −44 −48 −46.4 −64.4 −64.9 −66.1 pH 9.0 8.4 7.7 9.9 9.0 7.3

*The effect of 10 dwb% phosphate-based additives on the zeta potential and pH of 7 wt% bentonite slurries* 

<sup>−</sup> <sup>4</sup> *P O*2 7

<sup>−</sup> <sup>5</sup> *P O*3 10

<sup>−</sup> ( <sup>3</sup> )<sup>17</sup> *NaPO*

**Figure 14.**

**Table 1.**

**6. Outlook**

*sodium polyacrylate concentrations (Robles et al. [44]).*

water would be available to the population.

**Acknowledgements**

ANID/FONDAP/15130015.

*Herschel-Bulkley parameters (yield stress and flow index) of kaolin pulp in seawater at pH 8 with varied* 

particles. The authors studied the influence of sodium polyacrylate of low molecular weight on the performance and viscoelasticity of kaolin pulps in seawater. It was shown that the reagent could reduce the strength of the bonds between the particles through steric stabilisation, considerably lowering the yield stress (**Figure 14**).

It was interesting that this polymer of low molecular weight provides promising results in a highly saline medium since the main reports in the literature have given its efficiency to the induction of higher anionic charges on the surfaces [45, 46].

Tailings management in saline environments continues to be a challenging issue for plant design and operation, especially when significant clay content appears. Numerous factors enter the discussion, such as water quality, mineralogy (the type of clay), legal regulations, availability of water resources, etc. The need to improve the efficiency of this operation has increased in recent years, which has attracted greater scientific interest. Notable improvements have emerged from a technological point of view, in which the market offers increasingly robust equipment. That allows significant amounts of water to be extracted from the tailings and recycle them to upstream operations, with economic, environmental, and social benefits considering that many industries compete with neighbouring communities for disposing of the water resource. So reducing the water make-up means that more

The authors thank ANID/Fondecyt/11171036 and Centro CRHIAM Project

**134**

The authors declare no conflict of interest.

### **Author details**

Ricardo I. Jeldres1 \* and Matías Jeldres2

1 Department of Chemical Engineering and Mineral Processing, University of Antofagasta, Antofagasta, Chile

2 Faculty of Engineering and Architecture, Arturo Prat University, Antofagasta, Chile

\*Address all correspondence to: ricardo.jeldres@uantof.cl

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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[21] Jeldres, R. I.; Uribe, L.; Cisternas, L. A.; Gutierrez, L.; Leiva, W. H.; Valenzuela, J. The effect of clay minerals on the process of flotation of copper ores - A critical review. Appl. Clay Sci. 2019, 170, 57-69, doi:10.1016/j. clay.2019.01.013.

[22] Liu, D.; Edraki, M.; Fawell, P.; Berry, L. Improved water recovery: A review of clay-rich tailings and saline water interactions. Powder Technol. 2020, 364, 604-621, doi:10.1016/j. powtec.2020.01.039.

[23] Jeldres, R. I.; Piceros, E. C.; Wong, L.; Leiva, W. H.; Herrera, N.; Toledo, P. G. Dynamic moduli of flocculated kaolinite sediments: effect of salinity, flocculant dose, and settling time. Colloid Polym. Sci. 2018, 296, 1935- 1943, doi:10.1007/s00396-018-4420-x.

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[25] Johnson, S. B.; Franks, G. V.; Scales, P. J.; Boger, D. V.; Healy, T. W. Surface chemistry–rheology relationships in concentrated mineral suspensions. Int. J. Miner. Process. 2000, 58, 267-304, doi:10.1016/S0301-7516(99)00041-1.

[26] Jeldres, M.; Piceros, E.; Robles, P. A.; Toro, N.; Jeldres, R. I. Viscoelasticity of quartz and kaolin slurries in seawater: Importance of magnesium precipitates. Metals (Basel). 2019, 9, 1120, doi:10.3390/met9101120.

[27] Jeldres, R. I.; Piceros, E. C.; Leiva, W. H.; Toledo, P. G.; Quezada, G. R.; Robles, P. A.; Valenzuela, J. Analysis of silica pulp viscoelasticity in saline media: The effect of cation size. Minerals 2019, 9, 1-15, doi:10.3390/ min9040216.

[28] Quezada, G. R.; Rozas, R. E.; Toledo, P. G. Molecular dynamics simulations of quartz (101)-water and corundum (001)-water interfaces: Effect of surface charge and ions on cation adsorption, water orientation, and surface charge reversal. J. Phys. Chem. C 2017, 121, doi:10.1021/acs. jpcc.7b08836.

[29] Quezada, G. R.; Rozas, R. E.; Toledo, P. G. Ab initio calculations of partial charges at kaolinite edge sites and molecular dynamics simulations of cation adsorption in saline solutions at and above the pH of zero charge. J. Phys. Chem. C 2019, 123, 22971-22980, doi:10.1021/acs.jpcc.9b05339.

[30] Castillo, C.; Ihle, C. F.; Jeldres, R. I. Chemometric optimisation of a copper sulphide tailings flocculation process in the presence of clays. Minerals 2019, 9, 582, doi:10.3390/min9100582.

[31] Ma, X.; Fan, Y.; Dong, X.; Chen, R.; Li, H.; Sun, D.; Yao, S. Impact of clay minerals on the dewatering of coal slurry: An experimental and molecularsimulation Study. Minerals 2018, 8, 400, doi:10.3390/min8090400.

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gloenvcha.2017.04.004.

729.

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resources to water criticality, scarcity and climate change. Glob. Environ. Chang. 2017, 44, 109-124, doi:10.1016/j. [9] Fisher, D. T.; Clayton, S. A.; Boger, D. V.; Scales, P. J. The bucket rheometer for shear stress-shear rate measurement of industrial suspensions. J. Rheol. (N. Y. N. Y). 2007, 51, 821-831,

[10] Yoshimura, A.; Prud'homme, R. K. Wall slip corrections for couette and parallel disk viscometers. J. Rheol. (N. Y. N. Y). 1988, 32, 53-67,

[11] Hartnett, J. P.; Hu, R. Y. Z. Technical note: The yield stress—An engineering reality. J. Rheol. (N. Y. N. Y). 1989, 33,

[12] Barnes, H. A.; Walters, K. The yield stress myth? Rheol. Acta 1985, 24, 323-

[14] Sofrá, F.; Boger, D. V Environmental rheology for waste minimisation in the minerals industry. Chem. Eng. J. 2002, 86, 319-330, doi:10.1016/

671-679, doi:10.1122/1.550006.

326, doi:10.1007/BF01333960.

[13] de Kretser, R.; Scales, P. J.; Boger, D. V. Improving clay-based tailings disposal: Case study on coal tailings. AIChE J. 1997, 43, 1894-1903,

doi:10.1002/aic.690430724.

S1385-8947(01)00225-X.

[15] Adiansyah, J. S.; Rosano, M.; Vink, S.; Keir, G. A framework for a sustainable approach to mine tailings management: disposal strategies. J. Clean. Prod. 2015, 108, 1050-1062, doi:10.1016/j.jclepro.2015.07.139.

[16] McFarlane, A. J.; Bremmell, K. E.; Addai-Mensah, J. Optimising the dewatering behaviour of clay tailings through interfacial chemistry, orthokinetic flocculation and controlled shear. Powder Technol. 2005, 160, 27-34, doi:10.1016/j.powtec.2005.04.046.

[17] Cruz, N.; Forster, J.; Bobicki, E. R. Slurry rheology in mineral processing unit operations: A critical review. Can.

doi:10.1122/1.2750657.

doi:10.1122/1.549963.

[2] Cisternas, L. A.; Gálvez, E. D. The use of seawater in mining. Miner. Process. Extr. Metall. Rev. 2018, 39, 18-33, doi:10.1080/08827508.2017.1389

[3] Boger, D. V. Rheology of slurries and environmental impacts in the mining industry. Annu. Rev. Chem. Biomol. Eng. 2013, 4, 239-257, doi:10.1146/ annurev-chembioeng-061312-103347.

[4] Nguyen, Q. D.; Boger, D. V. Application of rheology to solving tailings disposal problems. Int. J. Miner. Process. 1998, 54, 217-233, doi:10.1016/

[5] Boger, D. V. Rheology and the Minerals Industry. Miner. Process. Extr. Metall. Rev. 2000, 20, 1-25, doi:10.1080/08827509908962460.

[6] Watson, A. H.; Corser, P. G.; Garces-Pardo, E. E.; López-Christian, T. E.; Vandekeybus, J. A comparison of alternative tailings disposal methods — the promises and realities. In Mine Waste 2010 -A.B. Fourie and R.J. Jewell

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[44] Robles, P.; Piceros, E.; Leiva, W. H.; Valenzuela, J.; Toro, N.; Jeldres, R. I. Analysis of sodium polyacrylate as a rheological modifier for kaolin suspensions in seawater. Appl. Clay Sci. 2019, 183, 105328, doi:10.1016/j. clay.2019.105328.

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*Clay Science and Technology*

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[41] Abu-Jdayil, B. Rheology of sodium and calcium bentonite–water dispersions: Effect of electrolytes and aging time. Int. J. Miner. Process. 2011, 98, 208-213, doi:10.1016/j.

[42] Moreno, P. A.; Aral, H.; Cuevas, J.; Monardes, A.; Adaro, M.; Norgate, T.; Bruckard, W. The use of seawater as process water at Las Luces coppermolybdenum beneficiation plant in Taltal (Chile). Miner. Eng. 2011, 24, 852- 858, doi:10.1016/j.mineng.2011.03.009.

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[44] Robles, P.; Piceros, E.; Leiva, W. H.; Valenzuela, J.; Toro, N.; Jeldres, R. I. Analysis of sodium polyacrylate as a rheological modifier for kaolin suspensions in seawater. Appl. Clay Sci. 2019, 183, 105328, doi:10.1016/j.

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[46] Huang, G.; Pan, Z.; Wang, Y. Synthesis of sodium polyacrylate copolymers as water-based

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doi:10.3390/min10040293.

**138**

## *Edited by Gustavo Morari Do Nascimento*

This book presents the state-of-the-art results of synthesis, characterization, modification, and technological applications of clays, clay minerals, and materials based on clay minerals, such as polymer–clay nanocomposites and clay hybrids. It also presents some important results obtained in the broad area of clays and clay materials characterization. Moreover, this book provides a comprehensive account of polymer and biopolymer–clay nanocomposites, the use of clay as adsorption materials of industrial pollutants, the ceramic industry, and the physical–chemical aspects of aqueous dispersions of clay and clay minerals. This book is beneficial for students, teachers, and researchers who are interested in expanding their knowledge about the use of clays in a diverse range of fields, including nanotechnology, biotechnology, environmental science, industrial remediation, pharmaceuticals, and so on.

Published in London, UK © 2021 IntechOpen © Roberto / iStock

Clay Science and Technology

Clay Science and Technology

*Edited by Gustavo Morari Do Nascimento*