**5.3. Heat resistance**

**5. Functional properties**

10 Current Topics in the Utilization of Clay in Industrial and Medical Applications

**5.1. Cation exchange property**

charge per 100 g of soil.

electrical conductivity in clay [21].

referred as interlayer cations.

**5.2. Electrical conductivity**

lowest electrical conductivity.

neous porous medium.

sheet [22]. Large-sized cations such as K<sup>+</sup>

ductivities of the matrix material and the pore fluid [23].

Cation exchange capacity is a property of soil introduced by clay and organic matters. It is the

[20] and described as the quantity of positively charged ions held by the negatively charged surface of clay minerals. It may also be termed as cation exchange capacity (CEC) that may be measured as a centimol positive charge per kg of soil or milli-equivalent (meq) of positive

Fine-grained particles of clay result in an increased surface area per unit mass. Smaller particle size (0.002–0.001 mm in diameter) results in a significantly higher surface area, where a large number of cations can be adsorbed. Theses adsorbed cations impart significant level of

Ionic substitution in the sheet structure produces useful modifications. Ions like Fe3+ and Al3+ are small enough to enter the tetrahedral coordination with oxygen and substitute Si4+. Similarly, cations like Mg2+, Fe2+, Fe3+, Li1+, Ni2+, and Cu2+ can substitute Al3+ in the octahedral

Clay particles are the porous materials. The pore fluid influences the electrical conductivity. The electrical conductivity (mS/m) of a porous material is the combination of electrical con-

Air, water, or saline water may be present in the pore. When the pore fluid is of low conductivity, for example, air or water, the bulk conductivity of clay mineral is contributed by the matrix material. Pore fluid having a higher electrical conductivity significantly enhances the total electrical conductivity of clay, for example, clay particles with a significant porosity level (40–50%), and saline water present in the pore; then the bulk conductivity is mainly the contribution of pore fluid. In this case, there would be negligible difference in the conductivities of sand and clay.

A higher content of clay particles with 2:1 structure present in montmorillonite sample produces an increased bulk electrical conductivity for non-saline soils [24]. This effect was attributed to the exchangeable cations or to proton transfer from the dissociation of interlayer water content. A reduced level of interlayer water contents in K-saturated clays resulted in the

Since the clay content, pore fluid, clay type, saline water, and water saturation influence the soil conductivity, the assessment of electrical conductivity of reservoir rock may be used to estimate these factors [25]. However, the variation in the distribution of liquid and solid phases introduces the variation and complication in the electrical conductivity of heteroge-

, and Cs+

, Na+

, K<sup>+</sup> , H+ )

are located between the layers and

capacity of soil to hold cations (generally Al3+, Ca2+, Mg2+, Mn2+, Zn2+, Cu2+, Fe2+, Na+

Montmorillonite is a good heat insulator, and heat-resistant effects are obtainable using it as an additive in any substance. This is an area of significant research to produce thermal barrier effects in composite material structure.

Thermal barrier properties of clay minerals had been used in heat-resistant and flameretardant applications. Nanoclay is currently used extensively and investigated in polymer composite to obtain an increased thermal stability and flame retardancy.

The variation in the expansion, under heat effects, for metals, polymers, and ceramics had been noted. Generally, the order of thermal expansion magnitude in polymer, metal, and ceramic may be indicated as follows:

Polymer > metal > ceramic.

This relative order is based on the values of linear thermal expansion coefficient which are in the range of 20–100, 3–20, and 3–5 ppm/° C for polymers, metals, and ceramics, respectively [26].

Therefore, an increased thermal stability of montmorillonite introduces its use as a filler in producing polymers to impart a low thermal expansion. However, enhancement in polymer thermal stability requires an increasing aspect ratio, and an aspect ratio of greater than 100 is useful.

### **5.4. Water sorption**

Water sorption is an important characteristic of natural clay particles. Clay particles can absorb or lose water in response to changes in humidity content in the ambient environment; when water is absorbed, it fills the spaces between the stacked silicate layers [27].

Montmorillonite typically exhibits a gradual dehydration and phase change to a stronger nonexpendable clay. The specific gravity of any type of clay is variable resulting from loss or gain of water. Most of the known clay types are available in nature as a mixture containing several varieties including carbonates, feldspars, micas, and quartz.

Several studies addressed the swelling behavior of montmorillonite. The interaction of montmorillonite with water introduces useful effects. Water molecules cause swelling in montmorillonite. This swelling is a result of complex montmorillonite-water interactions between particles and within the particle itself.

Water molecule adsorption and swelling of montmorillonite introduce hydrated states and hysteresis. The migration of counter-ion, initially bound to montmorillonite surface to the central interlayer plane, leads to swelling in montmorillonite. Therefore, charge locus in montmorillonite has a strong influence on swelling dynamics [28].

The variety of montmorillonite utilization in material and product performance is significant in recent literature. The following sections describe the important useful effects that are

Montmorillonite: An Introduction to Properties and Utilization

http://dx.doi.org/10.5772/intechopen.77987

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Dietary toxins, bacterial toxins, and metabolic toxins can be absorbed by clay to resist nausea, vomiting, and diarrhea. Montmorillonite-based product is indicated to work immediately on the digestive channel and bind the toxic substances resulting in their removal from the body

The effects of montmorillonite-zinc oxide hybrid on diarrhea, intestinal permeability, and morphology were investigated on a total of 180 piglets. Piglets were divided in five groups and studied for 2 weeks using dietary treatment with montmorillonite and montmorillonite-ZnO in diet. Importantly, results obtained indicated that the dietary addition of 500 mg/kg of Zn from MMT-ZnO was similar to 2000 mg/kg of Zn from ZnO, and more effective relative to montmorillonite alone or 500 mg/kg of Zn, from ZnO, for the growth enhancement of piglets, alleviating diarrhea, improving intestinal microflora, mucosal barrier integrity, and morphol-

The use of calcium montmorillonite (Nova Sil clay type) in human diet can diminish healthharming effects of aflatoxin-contaminated food. The study was based on a clinical trial of selected volunteers in the age range of 20–45 years. It included 23 males and 27 females. The volunteers received calcium montmorillonite low dose (1.5 g/day) and high dose (3 g/day) for

Laboratory analysis of blood and urine samples was performed prior and after trial. Hematology, liver and kidney function, electrolytes, vitamins A and E, and minerals were not significantly changed in any study group. The study indicated the protection of participant

Montmorillonite can be the source of mineral for bacterial nutrition and found to maintain the pH levels required for a sustained growth [34]. Several bacterial species differing in morphology, motility, and Gram reaction were assisted in respiration by montmorillonite. The research results obtained show the relationship between clay minerals (montmorillonite and

Another important obtainable effect is the resistance to tooth decay. Tooth decay can be resisted by filling micro-pore using a fluid resin which polymerizes *in situ* and creates a micromechanical interlock in the tooth structure. This bonding process is a selective substitution for tooth minerals. The use of montmorillonite as a reinforcing filler for dental adhesives (typi-

kaolinite), and population growth and ecology of microorganism in natural habitat.

cally methacrylate monomers with solvent and a photo initiator) may be possible.

weeks. The compliance to study trial by the volunteers was indicated as 99.1%.

obtainable using the selected type of montmorillonite.

**6.1. Resistant to nausea and diarrhea**

through the stool [31].

ogy of weaned pigs [32].

**6.2. Supportive to health and growth**

from adverse effects of aflatoxins [33].

**6.3. Resistance to tooth decay**

An important concern in clay mineral study is how the monovalent and divalent cations affect the swelling pattern of K<sup>+</sup> -, Na+ -, and Ca2+-montmorillonites.

Montmorillonite is a 2:1 clay mineral; that is, two tetrahedral sheets separated by one octahedral sheet. The montmorillonite platelets can be negatively charged when


In any of the above two (i and ii) cases, negative charge produced is compensated by interlayer ions. The hydration of interlayer cations produces swelling [29].

The small platelet size and stacking structure are indicated as complicated to accurately characterize through experiment. Therefore, molecular dynamic simulation (MDS) is a useful way of understanding the atomic level structure. MDS is useful to study montmorillonite structure including swelling and hydration of interlayer cations. MDS was performed for K<sup>+</sup> -, Na+ -, and Ca2+-montmorillonites with varying level of water content.

The valence of the cations showed a significant influence on montmorillonite-water system. Simulations indicate that the cation K<sup>+</sup> shows a strong interaction with dehydrated montmorillonite sheets; however, in case of hydrated montmorillonite sheets, cation Ca+ interacts strongly. Therefore, the layer spacing of simulated K<sup>+</sup> -, Na+ -, and Ca2+-montmorillonites was obvious.

The simultaneous measurement of swelling and swelling pressure was done using a researcher- developed cell [30]. Undisturbed clay samples at a defined swelling (0–75%) were removed from the cell and analyzed using SEM, FTIR, and ATR (micro- attenuated total reflectance) spectroscopy. Silicate (Si-O)-stretching region (1150–950 cm−1) showed significant changes with variation in swelling and orientation. It was found that the reduced particle size with increased swelling was related to increased misorientation of the clay platelets. The rearrangement of clay platelets was observed as a direct result of the breakdown of the clay particles with increased hydration.
