**Applications of Activated Carbons Obtained from Lignocellulosic Materials for the Wastewater Treatment**

Ma. del Rosario Moreno-Virgen, Rigoberto Tovar-Gómez, Didilia I. Mendoza-Castillo and Adrián Bonilla-Petriciolet *Instituto Tecnológico de Aguascalientes México* 

#### **1. Introduction**

Activated carbons are used in a number of industrial applications including separation and purification technologies, catalytic processes, biomedical engineering, and energy storage, among others. The extensive application of activated carbon is mainly due to its relatively lowcost with respect to other adsorbents, wide availability, high performance in adsorption processes, surface reactivity and the versatility to modify its physical and chemical properties for synthesizing adsorbents with very specific characteristics (Haro et al., 2011). In particular, the adsorption on activated carbon is the most used method for wastewater treatment because it is considered a low-cost purification process where trace amounts of several pollutants can be effectively removed from aqueous solution. Recently, the demand of activated carbons has increased significantly as a water-purifying agent to reduce the environmental risks caused by the water pollution worldwide (Altenor et al., 2009; Bello-Huitle et al., 2010).

Traditionally, the activated carbons used in wastewater treatment are obtained from coal/lignite, wood or animal bones but, recently, there is a growing interest in the use of alternative and low-cost precursors for their production (Altenor et al., 2009; Elizalde-González & Hernández-Montoya, 2007; Mohamed et al., 2010). Specifically, lignocellulosic wastes are a low-cost natural carbon source for the synthesis of several materials including the production of activated carbons. In this context, it is convenient to remark that natural resources play a dominant role in the economic activities and the utilization of lignocellulosic wastes for the synthesis of valuable commercial products may contribute to the economic development and to prevent environment pollution especially in developing countries (Satyanarayana et al., 2007). Therefore, lignocellulosic materials are considered as an interesting and important natural resource for production of activated carbons based on the fact that several billion tons of these materials are available (Mohamed et al., 2010; Satyanarayana et al., 2007). Actually, these precursors are considered as the most appropriate candidates for a cost-effective preparation of activated carbons (Silvestre-Albero et al., 2012).

obtained from lignocellulosic precursor have been mainly used for the removal of heavy

Lignocellulosic Materials for the Wastewater Treatment 59

*Pollutant Precursors Physical Chemical* 

*Terminalia* 

Apricot/Peach stones, Nut shells, *Havea braziliansis* sawdust, *Pinus sylvestris* sawdust, Peanut husk, Date pits, Oak cups pulp, *Terminalia arjuna* nut, *Casurina equisetifolia* leaves, *Spartina alterniflora* plant, Olive stone, Olive waste cakes, Cane sugar bagasse, African palm pit, Pecan nut shells, Chestnut shell, Grapeseed, Hazelnut shell, Coconut shells, Coir pith, Maize stalks

Mango seed, Guava seed, Mango husk, Orange seed, *Loofa egyptiaca* plant, Cane bagasse, Olive seeds, Rice straw, Bamboo, Coffee husk, Peanut hull, Pistachio shell, Oak cups pulp, Palm kernel shell, Apricot shell, Bagasse, Fir wood, Avocado kernel seed, *Posidonia oceanic (L)* dead leaves, Coconut

*Havea Brazilians* sawdust, Oak cups pulp, Cedar wood, Fir wood, Brewer's spent grain lignin, Cashew nut shell, Pecan nuts, Peach stones, Kenaf, Rapessed, Almond Shell, Vine shoot, Oil palm fruit bunch

Table 1. Lignocellulosic precursors and activating agents used in the synthesis of activated

It appears that the most studied precursors are bamboo, cane bagasse, olive wastes, plants and fruit wastes. It is important to remark that different activating agents can be used for improving the adsorption properties of these carbons and they include, for example, KOH, ZnCl2, H2SO4, H3PO4, HNO3 and CO2. However, the chemical activation with both ZnCl2 and H3PO4 appears to be the most used procedure for the preparation of adsorbents for water purification. As stated in Chapter 3, H3PO4 is a widely used activating agent for the preparation of activated carbons for wastewater treatment probably due to it can be removed easily after carbon activation by washing with hot and cold water besides its other operational and environmental advantages. On the other hand, the carbonization temperature usually used for the synthesis of these adsorbent ranges from 400 to 1000 °C. A summary of representative textural properties of some activated carbons are reported in Table 2. As expected, these activated carbons show a wide range of textural properties and

*Common activating agent* 

CO2, H2O, Air H3PO4, HNO3,

H2O, CO2 K2CO3, H3PO4,

H3PO4, AlCl3, HCl, H2SO4, KOH, NaOH, ZnCl2, HNO3, FeCl3, CaCl2, K2CO3

ZnCl2, KOH, FeCl3, CaCl2, K2CO3

ZnCl2, H2SO4, KOH, ZrOCl2, HNO3

Air, CO2, SO2,

H2O, O2

metals, dyes and phenol compounds.

Applications of Activated Carbons Obtained from

Heavy metals *Arundo donax* plant canes,

Dyes Pecan nutshells, Castile nutshells,

plant, bagasse, palm Organic and sawdust, Oak cups

shells

carbons for wastewater treatment and desalination.

Organic and inorganic pollutants (e.g., citric acid, phenol, paranitrophenol; pharmaceuticals, fluorides)

The production of activated carbons from lignocellulosic wastes is usually justified by two factors: the unique properties of these precursors and the possibility of mass production at an affordable cost. Several studies reported in literature indicate that it is possible to produce high quality activated carbons from raw lignocellulosic materials. These carbons are suitable for different applications including the removal of various pollutants from both drinking water and wastewaters. These pollutants include dyes, heavy metals, fluorides, phenols and other organic and inorganic toxic compounds, which are considered as priority substances for wastewater treatment in several countries (Altenor et al., 2009).

As indicated in Chapter 1, several raw lignocellulosic materials are available worldwide and they have been used in the synthesis of activated carbons for water purification. The performance of these activated carbons in the removal of a specific pollutant depends on both the surface chemistry and the textural properties (Altenor et al., 2009; Elizalde-González & Hernández-Montoya, 2007). Specifically, the properties of activated carbons such as the surface area, the pore size distribution, the presence of functional groups, and other physical and chemical parameters play an important role in the adsorption process of a given pollutant (Altenor et al., 2009). Previous chapters showed that these properties of activated carbon are mainly function of the precursor and of the type of thermal and activation process (Elizalde-González & Hernández-Montoya, 2007; Mohamed et al., 2010). As expected, activated carbons obtained from different precursors and synthesis procedures will show different adsorption properties for the removal of a given pollutant.

Considering the importance of these materials in the context of environmental pollution control, this chapter provides an overview of the application of activated carbons obtained from lignocellulosic precursors for wastewater treatment. This chapter summarizes studies reported mainly from the year 2000. Our analysis and discussion are focused on the performance of different activated carbons obtained from several precursors and their capabilities for the removal of relevant and toxic pollutants from water. The remainder of this chapter is organized as follows. In Section 2, we briefly introduce the activated carbon types obtained from different precursors and synthesis procedures used in the context of wastewater treatment. This discussion also comprises the use of several activated carbons for the removal of priority water pollutants. Section 3 provides the description of removal mechanisms, while some key aspects of carbon regeneration are reported in Section 4. Finally, in Section 5 we provide some remarks and conclusions about the application of lignocellulosic precursors for producing activated carbons for wastewater treatment and desalination.

#### **2. Description of activated carbons for wastewater treatment and desalination**

#### **2.1 Synthesis, precursors and properties**

To date, different lignocellulosic precursors have been used for the synthesis of activated carbons for water treatment. As stated in Chapter 2, activated carbons can be obtained from a variety of raw lignocellulosic materials and by different processing methods. Table 1 shows a summary of the most common precursors and synthesis conditions, including physical and chemical activation agents, used for the preparation of activated carbons for the removal of priority water pollutants. In general, a wide variety of activated carbons

58 Characterization Techniques and Applications in the Wastewater Treatment

The production of activated carbons from lignocellulosic wastes is usually justified by two factors: the unique properties of these precursors and the possibility of mass production at an affordable cost. Several studies reported in literature indicate that it is possible to produce high quality activated carbons from raw lignocellulosic materials. These carbons are suitable for different applications including the removal of various pollutants from both drinking water and wastewaters. These pollutants include dyes, heavy metals, fluorides, phenols and other organic and inorganic toxic compounds, which are considered as priority

As indicated in Chapter 1, several raw lignocellulosic materials are available worldwide and they have been used in the synthesis of activated carbons for water purification. The performance of these activated carbons in the removal of a specific pollutant depends on both the surface chemistry and the textural properties (Altenor et al., 2009; Elizalde-González & Hernández-Montoya, 2007). Specifically, the properties of activated carbons such as the surface area, the pore size distribution, the presence of functional groups, and other physical and chemical parameters play an important role in the adsorption process of a given pollutant (Altenor et al., 2009). Previous chapters showed that these properties of activated carbon are mainly function of the precursor and of the type of thermal and activation process (Elizalde-González & Hernández-Montoya, 2007; Mohamed et al., 2010). As expected, activated carbons obtained from different precursors and synthesis procedures

Considering the importance of these materials in the context of environmental pollution control, this chapter provides an overview of the application of activated carbons obtained from lignocellulosic precursors for wastewater treatment. This chapter summarizes studies reported mainly from the year 2000. Our analysis and discussion are focused on the performance of different activated carbons obtained from several precursors and their capabilities for the removal of relevant and toxic pollutants from water. The remainder of this chapter is organized as follows. In Section 2, we briefly introduce the activated carbon types obtained from different precursors and synthesis procedures used in the context of wastewater treatment. This discussion also comprises the use of several activated carbons for the removal of priority water pollutants. Section 3 provides the description of removal mechanisms, while some key aspects of carbon regeneration are reported in Section 4. Finally, in Section 5 we provide some remarks and conclusions about the application of lignocellulosic precursors for producing activated carbons for wastewater treatment and

**2. Description of activated carbons for wastewater treatment and desalination** 

To date, different lignocellulosic precursors have been used for the synthesis of activated carbons for water treatment. As stated in Chapter 2, activated carbons can be obtained from a variety of raw lignocellulosic materials and by different processing methods. Table 1 shows a summary of the most common precursors and synthesis conditions, including physical and chemical activation agents, used for the preparation of activated carbons for the removal of priority water pollutants. In general, a wide variety of activated carbons

substances for wastewater treatment in several countries (Altenor et al., 2009).

will show different adsorption properties for the removal of a given pollutant.

desalination.

**2.1 Synthesis, precursors and properties** 

obtained from lignocellulosic precursor have been mainly used for the removal of heavy metals, dyes and phenol compounds.


Table 1. Lignocellulosic precursors and activating agents used in the synthesis of activated carbons for wastewater treatment and desalination.

It appears that the most studied precursors are bamboo, cane bagasse, olive wastes, plants and fruit wastes. It is important to remark that different activating agents can be used for improving the adsorption properties of these carbons and they include, for example, KOH, ZnCl2, H2SO4, H3PO4, HNO3 and CO2. However, the chemical activation with both ZnCl2 and H3PO4 appears to be the most used procedure for the preparation of adsorbents for water purification. As stated in Chapter 3, H3PO4 is a widely used activating agent for the preparation of activated carbons for wastewater treatment probably due to it can be removed easily after carbon activation by washing with hot and cold water besides its other operational and environmental advantages. On the other hand, the carbonization temperature usually used for the synthesis of these adsorbent ranges from 400 to 1000 °C. A summary of representative textural properties of some activated carbons are reported in Table 2. As expected, these activated carbons show a wide range of textural properties and

maize talks, pecan nut, olive wastes and coir pith, among others. Both chemical and physical activation procedures have been used for the preparation of activated carbons for removal

Lignocellulosic Materials for the Wastewater Treatment 61

500 Cadmium Nickel

H3PO4 400 – 700 Cadmium Wang et al. (2011)

H3PO4, Air 400 – 1000 Copper Puziy et al. (2007)

Chestnut shell ZnCl2 550 Copper Ozcimen & Ersoy-Mericboyu

Grapeseed ZnCl2 550 Copper Ozcimen & Ersoy-Mericboyu

Pecan shell Air, H3PO4 300 – 500 Copper Dastgheib & Rockstraw (2001)

Olive wastes H3PO4 350 – 650 Copper Baccar et al. (2009)

Oak cups pulp H3PO4, ZnCl2 600 Chromium Timur et al. (2010)

Maize talks KOH 700 Lead El-Hendawy (2009)

Table 3. Synthesis conditions of activated carbons obtained from lignocellulosic precursors

Chromium is considered a hazardous pollutant worldwide because of it is a mutagen and potential carcinogen. This pollutant is generated by several industries including metallurgy, leather tanning, and electroplating. In particular, water pollution caused by chromium is an important environmental problem in México and other developing countries. Until now, different lignocellulosic precursors have been used for the preparation of activated carbon for chromium removal. For example, Álvarez et al. (2007) reported the chromium adsorption using activated carbons obtained from *Pinus sylvestris* sawdust and different

*Pollutant Reference* 

(2008)

(2008)

800 Lead Hernández-Montoya et al. (2011)

de Lima et al. (2011)

Gimba et al. (2009)

Namasivayam & Sangeetha (2006)

450 – 650 Chromium Álvarez et al. (2007)

Cadmium Chromium

HNO3, Steam 900 Lead Giraldo & Moreno-Piraján (2008)

HNO3, Steam 900 Lead Giraldo & Moreno-Piraján (2008)

Copper Mercury

Mercury Chromium Basso et al. (2002)

of metal ions. Some illustrative applications are described below.

Nut shells H3PO4, SO2 475 Cadmium Tajar et al. (2009)

Applications of Activated Carbons Obtained from


surface chemistry which are determined by the conditions of the production process. For example, the studied activated carbons for wastewater treatment have surface areas from 100 to 1000 m2/g.

#### **2.2 Applications in wastewater treatment and desalination**

#### **2.2.1 Heavy metals**

60 Characterization Techniques and Applications in the Wastewater Treatment

surface chemistry which are determined by the conditions of the production process. For example, the studied activated carbons for wastewater treatment have surface areas from

Water pollution by heavy metals is considered a serious environmental problem due to their toxicity, long persistence, bioaccumulation and biomagnifications in food chain (Wojnarovits et al., 2010). In fact, heavy metals are toxic to aquatic flora, animals and human beings even at relatively low concentrations (Tajar et al., 2009). Chromium, cadmium and lead are considered the most common hazardous metals found in wastewaters of several industries. Particularly, the adsorption of these heavy metals on activated carbons is the most used treatment method to reach water pollution regulations and environmental standards. A great variety of lignocellusic precursors and activating agents has been used for the preparation of activated carbons for heavy metal removal (see Table 3). In general, these precursors include plant canes, chestnut shell, cane sugar bagasse, coconut shell,

100 to 1000 m2/g.

maize talks, pecan nut, olive wastes and coir pith, among others. Both chemical and physical activation procedures have been used for the preparation of activated carbons for removal of metal ions. Some illustrative applications are described below.


Chromium is considered a hazardous pollutant worldwide because of it is a mutagen and potential carcinogen. This pollutant is generated by several industries including metallurgy, leather tanning, and electroplating. In particular, water pollution caused by chromium is an important environmental problem in México and other developing countries. Until now, different lignocellulosic precursors have been used for the preparation of activated carbon for chromium removal. For example, Álvarez et al. (2007) reported the chromium adsorption using activated carbons obtained from *Pinus sylvestris* sawdust and different

and citric acid (Sreejalekshmit et al., 2009). Note that metal processing industries may discharge several pollutants including both heavy metals and organic chelating ligands such as citric acid and tartaric acid. Based on this fact, it is convenient to study the adsorption performance of activated carbons in multicomponent systems. These authors concluded that the presence of citric acid improves the adsorption capacity of this activated carbon. It appears that the functional –COOH groups of the adsorbed citric acid acted as new adsorption sites for lead on the activated carbon surface. Other adsorbents obtained from chemical activation of coconut shells (Gimba et al., 2009) and maize talks (El-Hendawy, 2009) can be used for lead adsorption. In particular, the synthesis of high performance activated carbons is feasible using maize talks and KOH activation. This adsorbent may show lead adsorption capacities up to 347 mg/g. Note that recent studies have showed that it is possible to use natural wastes (e.g., egg shell residues) to produce alternative and lowcost activating agents for improving the adsorption properties of activated carbons for heavy metal removal (Hernández-Montoya et al., 2011). One example is the activated carbon obtained from pecan nutshells, H3PO4 and a calcium solution extracted from egg shells,

Lignocellulosic Materials for the Wastewater Treatment 63

Finally, removal studies for other heavy metals include the adsorption of mercury using coconut shell activated carbons (Gimba et al., 2009), the removal of nickel and mercury using ZnCl2 activated coir pith carbon (Namasivayam & Sangeetha, 2006), and the copper adsorption employing carbons from pecan shell (Dastgheib & Rockstraw, 2001), fruit stones (Puziy et al., 2007), hazelnut shell (Dermibas et al., 2009), chestnut shell and grapeseed (Ozcimen & Ersoy-Mericboyu, 2009), olive-waste (Baccar et al., 2009) and coconut palm (de

calcium

*°C* 

Pecan shell Copper 2 – 5 25 33 - 40 Dastgheib & Rockstraw (2001)

African palm pit Lead 2 – 8 25 4.7 – 15.2 Giraldo & Moreno-Piraján

Cane sugar bagasse Lead 2 – 8 25 6.4 – 13.7 Giraldo & Moreno-Piraján

Table 4. Adsorption capacities of selected activated carbons obtained from lignocellulosic

In general, literature indicates that the chemical activation using HNO3 and H3PO4 improves the adsorption properties of activated carbons for heavy metal removal (Giraldo & Moreno-Piraján, 2008; Puziy et al., 2007). Specially, the presence of heteroatoms, in particular oxygen, may enhance the adsorption properties of these adsorbents. In summary, the adsorption

Maize talks Lead - 25 88 - 347 El-Hendawy (2009) Pecan nut Lead 5 30 75.4 Hernández-Montoya et al.

*Arundo donax* plant Nickel 5.8 28 25.8 Basso et al. (2002)

Chromium 1 – 9 - 0.5 – 1.83 Álvarez et al. (2007)

*qmax, mg/g Reference* 

(2008)

(2008)

(2011)

 *Conditions* 

*Arundo donax* plant Cadmium 5.8 28 57.3 Basso et al. (2002) Nut shells Cadmium 6 25 90 - 120 Tajar et al. (2009)

which have been used for the removal of lead ions.

Applications of Activated Carbons Obtained from

*Precursor Pollutant pH T,* 

precursors for heavy metal removal from water.

Lima et al., 2011).

*Pinus sylvestris* sawdust

activation procedures. The activated carbons obtained from this precursor and different activating agents (i.e., HCl, H3PO4, H2SO4, AlCl3, NaOH) showed different textural properties. This study suggested that the chromium adsorption may be controlled by a chemical or physical mechanism depending upon the used carbon activating agent. In general, activated carbons obtained with acid treatments exhibited the highest chromium adsorption especially those obtained by H3PO4 treatment. In other study, Timur et al. (2010) prepared activated carbons from oak cups pulp using H3PO4 and ZnCl2 for chromium removal. These carbons have similar adsorption capacities, which are higher than 140 mg/g. These adsorption capacities are higher than those obtained from other lignocellusosic precursors treated with ZnCl2 such as *Terminalia arjuna* nut (28 mg/g) and *Casurina equisetifolia* leaves (35 mg/g). Activated carbons prepared from coconut shell have been also used for chromium removal from water (de Lima et al., 2011). In particular, these adsorbents may show adsorption capacities up to 10 mg/g.

On the other hand, cadmium is also an important heavy metal in the context of environmental pollution control because its presence in water, even at very low concentrations, is harmful to aquatic environment and human health (Wang et al., 2011). This metal is also considered as a priority water pollutant in several countries. Several raw lignocellulosic materials have been employed as precursors for the preparation of activated carbons for cadmium adsorption. For example, Basso et al. (2002) studied the preparation of activated carbons from *Arundo donax* plant canes and phosphoric acid activation for the removal of cadmium and nickel ions. *Arundo donax L.* belongs to grass species and is a plant that attains heights of 40 ft and tends to form large, continuous root masses (Basso et al., 2002). This plant is considered as one of the most promising grass species for non-food uses because of it high biomass yield potential. Several activated carbons were prepared using this precursor at different atmospheres (i.e., air, CO2 and N2). This study concluded that activated carbons with the highest total content of surface oxygen functional groups showed the best adsorption capacity for heavy metal removal. A nut shell-based activated carbon obtained by chemical activation using H3PO4 and SO2 has been also studied (Tajar et al., 2009). The surface modification of activated carbon from nutshells using these activation agents improves the cadmium adsorption properties. In other study, activated carbons obtained from coconut shells and different activating salts (FeCl3, ZnCl2, CaCl2 and K2CO3) were employed for adsorption of cadmium ions (Gimba et al., 2009). In particular, adsorbents treated with CaCl2 and K2CO3 showed the best removal performance. Alternatively, other precursors such as *Spartina alterniflora* plant (Wang et al., 2011) and coconut shell (de Lima et al., 2011) can be used for preparing adsorbents for cadmium removal.

Lead has been classified as a serious hazardous heavy metal because of it is extremely toxic for human beings. This metal is commonly detected in several industrial wastewaters from mining, smelting, metal plating and dying processes. Therefore, special attention has been given to develop proper adsorbents for lead removal from water. Specifically, Giraldo & Moreno-Piraján (2008) reported the adsorption of lead ions using activated carbons with high surface area obtained from cane sugar bagasse and African palm pit. These precursors were activated using HNO3. In other study, activated carbons obtained from single step steam pyrolysis of sawdust of rubber wood were used for the simultaneous removal of lead

62 Characterization Techniques and Applications in the Wastewater Treatment

activation procedures. The activated carbons obtained from this precursor and different activating agents (i.e., HCl, H3PO4, H2SO4, AlCl3, NaOH) showed different textural properties. This study suggested that the chromium adsorption may be controlled by a chemical or physical mechanism depending upon the used carbon activating agent. In general, activated carbons obtained with acid treatments exhibited the highest chromium adsorption especially those obtained by H3PO4 treatment. In other study, Timur et al. (2010) prepared activated carbons from oak cups pulp using H3PO4 and ZnCl2 for chromium removal. These carbons have similar adsorption capacities, which are higher than 140 mg/g. These adsorption capacities are higher than those obtained from other lignocellusosic precursors treated with ZnCl2 such as *Terminalia arjuna* nut (28 mg/g) and *Casurina equisetifolia* leaves (35 mg/g). Activated carbons prepared from coconut shell have been also used for chromium removal from water (de Lima et al., 2011). In particular, these adsorbents

On the other hand, cadmium is also an important heavy metal in the context of environmental pollution control because its presence in water, even at very low concentrations, is harmful to aquatic environment and human health (Wang et al., 2011). This metal is also considered as a priority water pollutant in several countries. Several raw lignocellulosic materials have been employed as precursors for the preparation of activated carbons for cadmium adsorption. For example, Basso et al. (2002) studied the preparation of activated carbons from *Arundo donax* plant canes and phosphoric acid activation for the removal of cadmium and nickel ions. *Arundo donax L.* belongs to grass species and is a plant that attains heights of 40 ft and tends to form large, continuous root masses (Basso et al., 2002). This plant is considered as one of the most promising grass species for non-food uses because of it high biomass yield potential. Several activated carbons were prepared using this precursor at different atmospheres (i.e., air, CO2 and N2). This study concluded that activated carbons with the highest total content of surface oxygen functional groups showed the best adsorption capacity for heavy metal removal. A nut shell-based activated carbon obtained by chemical activation using H3PO4 and SO2 has been also studied (Tajar et al., 2009). The surface modification of activated carbon from nutshells using these activation agents improves the cadmium adsorption properties. In other study, activated carbons obtained from coconut shells and different activating salts (FeCl3, ZnCl2, CaCl2 and K2CO3) were employed for adsorption of cadmium ions (Gimba et al., 2009). In particular, adsorbents treated with CaCl2 and K2CO3 showed the best removal performance. Alternatively, other precursors such as *Spartina alterniflora* plant (Wang et al., 2011) and coconut shell (de Lima et al., 2011) can be used for preparing adsorbents for cadmium

Lead has been classified as a serious hazardous heavy metal because of it is extremely toxic for human beings. This metal is commonly detected in several industrial wastewaters from mining, smelting, metal plating and dying processes. Therefore, special attention has been given to develop proper adsorbents for lead removal from water. Specifically, Giraldo & Moreno-Piraján (2008) reported the adsorption of lead ions using activated carbons with high surface area obtained from cane sugar bagasse and African palm pit. These precursors were activated using HNO3. In other study, activated carbons obtained from single step steam pyrolysis of sawdust of rubber wood were used for the simultaneous removal of lead

may show adsorption capacities up to 10 mg/g.

removal.

and citric acid (Sreejalekshmit et al., 2009). Note that metal processing industries may discharge several pollutants including both heavy metals and organic chelating ligands such as citric acid and tartaric acid. Based on this fact, it is convenient to study the adsorption performance of activated carbons in multicomponent systems. These authors concluded that the presence of citric acid improves the adsorption capacity of this activated carbon. It appears that the functional –COOH groups of the adsorbed citric acid acted as new adsorption sites for lead on the activated carbon surface. Other adsorbents obtained from chemical activation of coconut shells (Gimba et al., 2009) and maize talks (El-Hendawy, 2009) can be used for lead adsorption. In particular, the synthesis of high performance activated carbons is feasible using maize talks and KOH activation. This adsorbent may show lead adsorption capacities up to 347 mg/g. Note that recent studies have showed that it is possible to use natural wastes (e.g., egg shell residues) to produce alternative and lowcost activating agents for improving the adsorption properties of activated carbons for heavy metal removal (Hernández-Montoya et al., 2011). One example is the activated carbon obtained from pecan nutshells, H3PO4 and a calcium solution extracted from egg shells, which have been used for the removal of lead ions.

Finally, removal studies for other heavy metals include the adsorption of mercury using coconut shell activated carbons (Gimba et al., 2009), the removal of nickel and mercury using ZnCl2 activated coir pith carbon (Namasivayam & Sangeetha, 2006), and the copper adsorption employing carbons from pecan shell (Dastgheib & Rockstraw, 2001), fruit stones (Puziy et al., 2007), hazelnut shell (Dermibas et al., 2009), chestnut shell and grapeseed (Ozcimen & Ersoy-Mericboyu, 2009), olive-waste (Baccar et al., 2009) and coconut palm (de Lima et al., 2011).


Table 4. Adsorption capacities of selected activated carbons obtained from lignocellulosic precursors for heavy metal removal from water.

In general, literature indicates that the chemical activation using HNO3 and H3PO4 improves the adsorption properties of activated carbons for heavy metal removal (Giraldo & Moreno-Piraján, 2008; Puziy et al., 2007). Specially, the presence of heteroatoms, in particular oxygen, may enhance the adsorption properties of these adsorbents. In summary, the adsorption

industry and they are considered priority pollutants due to its high toxicity and carcinogenic potential (Hernández-Montoya et al., 2011). However, few adsorption studies have been

Lignocellulosic Materials for the Wastewater Treatment 65

Woods are the most common used precursors for preparing activated carbons for dye removal. During long time, wood activated carbons obtained from different chemical and physical treatments have been used for the removal of several dyes including Acid Blue 74, Basic Brown 1, and Methylene Blue (Wu et al., 2005). Additionally, bamboo wastes have been widely employed as a raw material for the synthesis of activated carbons for dye removal (Ahmad & Hameed, 2010; Chan et al., 2008; Chan et al., 2009). Results of adsorption studies suggested that both surface area and porosity of these activated carbons play an important role in the removal process. Other precursors reported for dye removal include sugar industry wastes (Blanco-Castro et al., 2000), coir pith (Namasivayam & Sangeetha, 2006), and coconut shells (Gimba et al., 2009), among other raw lignocellulosic materials.

It is convenient to remark that several fruits and crops have been considered as effective precursors for preparation of adsorbents for dye removal. Specifically, Elizalde-González et al. (2007) reported the adsorption of several basic, acid and reactive dyes from aqueous solutions by avocado activated carbons impregnated with H3PO4. In other study, Elizalde-Gonzalez & Hernandez-Montoya (2008) reported the removal of anthraquinone dyes (i.e., acid blue 80 and acid green 27) using activated carbons obtained from seeds of mango, guava and orange. These fruits are abundant and are considered as a low cost agricultural waste in México and other countries (Elizalde-González & Hernández-Montoya, 2009). These studies indicated that the acid activated carbon obtained from orange seed was the most effective for the removal of acid green 27 from water despite its negligible specific surface; while the activated carbons obtained from mango seed were more effective for the removal of acid blue 80. Authors concluded that the interaction between the functional groups of activated carbons and these dyes are very important in the adsorption process. In other study, guava seed was used as precursor of activated carbon for the removal of Acid orange 7 (AO7), which is a dye commonly used in tanneries, paper manufacturing and textile industry (Elizalde-Gónzalez & Hernández-Montoya, 2009). The optimal conditions for the preparation of guava seed carbon for dye removal were identified using a Taguchi experimental design. Recently, Bello-Huitle et al. (2010) reported the removal of methylene blue dye from water using activated carbons obtained from pecan and castile nutshells. Both pecan and castile nutshells are important crops from México and other countries. In this study, H3PO4 was used as activating agent for these precursors. Adsorption studies indicated that the adsorption capacity of activated carbon obtained from pecan nutshells was higher than that obtained for castile nutshells. Finally, Hernández-Montoya et al. (2011) have reported the preparation of activated carbons for adsorption of acid blue 25 using both pecan nut shells and a calcium solution extracted from egg shell wastes. This adsorbent

With respect to precursors obtained from plant wastes, El-Ashtoukhy (2009) used the *Loofa egyptiaca* plant to prepare a low-cost activated carbon for the removal of direct blue 106. This plant is cultivated only in Egypt and is a highly branched, fibrous and interconnected cellulosic material. In this study, the adsorbents were obtained from the carbonization of

performed using these acid dyes.

Applications of Activated Carbons Obtained from

showed adsorption capacities up to 48 mg/g.

capacities of lignocellulosic activated carbons for heavy metals may range from 10 to 100 mg/g depending on the precursor type and activation procedure. Adsorption capacities for selected lignocellulosic activated carbons are reported in Table 4.

#### **2.2.2 Dyes**

Water pollution by dyes is an important environmental problem because these pollutants are toxic and may be carcinogenic. Dyes can affect the physical and chemical properties of water and the aquatic flora and fauna. It has been estimated that about 7 X 105 tons of dyes are generated annually worldwide by several industrial activities. In general, dyes exhibit a wide range of different chemical structures and properties and can be classified according to chemical constitution, application and end use. Typical dyes used in industrial processes include acid, basic, direct, disperse and reactive (Dermibas, 2009). In general, dyes are usually resistant to classical biodegradation and the adsorption process is an effective treatment method for their removal (Demirbas et al., 2009). Table 5 reports some examples of activated carbons used for dye removal from water.


Table 5. Synthesis conditions of activated carbons obtained from lignocellulosic precursors for dye removal.

Recently, Altenor et al. (2009) have reported a review of activated carbons obtained from lignocellulosic wastes for water treatment giving an emphasis to those adsorbents used for dye removal. Literature review indicates that several adsorption studies using activated carbons for acid dyes have been reported. It is convenient to observe that antraquinone acid dyes (e.g., acid blue 25) are the second most important dyes commercially used in the textile

*Pollutant Reference* 

Chan et al. (2008) Chan et al. (2009)

Wu et al. (2005)

Timur et al. (2010)

Acid yellow 117

Basic brown 1 Methylene blue

Acid Red 111 Methylene Blue

500 – 800 Indigo blue Gimba et al. (2009)

500 Direct blue 106 El-Ashtoukhy (2009)

800 Acid blue 25 Hernández-Montoya et al.

(2011)

64 Characterization Techniques and Applications in the Wastewater Treatment

capacities of lignocellulosic activated carbons for heavy metals may range from 10 to 100 mg/g depending on the precursor type and activation procedure. Adsorption capacities for

Water pollution by dyes is an important environmental problem because these pollutants are toxic and may be carcinogenic. Dyes can affect the physical and chemical properties of water and the aquatic flora and fauna. It has been estimated that about 7 X 105 tons of dyes are generated annually worldwide by several industrial activities. In general, dyes exhibit a wide range of different chemical structures and properties and can be classified according to chemical constitution, application and end use. Typical dyes used in industrial processes include acid, basic, direct, disperse and reactive (Dermibas, 2009). In general, dyes are usually resistant to classical biodegradation and the adsorption process is an effective treatment method for their removal (Demirbas et al., 2009). Table 5 reports some examples

> *Carbonization temperature, ºC*

Castile nutshells H3PO4 500 Methylene blue Bello-Huitle et al. (2010)

780, 900 Acid blue 74

600 Basic Red 18

ZnCl2 600 Methylene blue Dural et al. (2011)

Pecan nutshells H3PO4 500 Methylene blue Bello-Huitle et al. (2010)

Table 5. Synthesis conditions of activated carbons obtained from lignocellulosic precursors

Recently, Altenor et al. (2009) have reported a review of activated carbons obtained from lignocellulosic wastes for water treatment giving an emphasis to those adsorbents used for dye removal. Literature review indicates that several adsorption studies using activated carbons for acid dyes have been reported. It is convenient to observe that antraquinone acid dyes (e.g., acid blue 25) are the second most important dyes commercially used in the textile

selected lignocellulosic activated carbons are reported in Table 4.

of activated carbons used for dye removal from water.

*agent* 

ZnCl2, CaCl2, K2CO3

KOH

HNO3, ZnCl2

ZnCl2

Calcium solution

Bamboo H3PO4 400 – 600 Acid blue 25

*Precursor Activating* 

Coconut shell FeCl3,

Fit wood H2O,

*Loofa egyptiaca* plant H3PO4,

Oak cups pulp H3PO4,

Pecan nut shells H3PO4,

*P. oceanica* (*L*) dead

for dye removal.

leaves

**2.2.2 Dyes** 

industry and they are considered priority pollutants due to its high toxicity and carcinogenic potential (Hernández-Montoya et al., 2011). However, few adsorption studies have been performed using these acid dyes.

Woods are the most common used precursors for preparing activated carbons for dye removal. During long time, wood activated carbons obtained from different chemical and physical treatments have been used for the removal of several dyes including Acid Blue 74, Basic Brown 1, and Methylene Blue (Wu et al., 2005). Additionally, bamboo wastes have been widely employed as a raw material for the synthesis of activated carbons for dye removal (Ahmad & Hameed, 2010; Chan et al., 2008; Chan et al., 2009). Results of adsorption studies suggested that both surface area and porosity of these activated carbons play an important role in the removal process. Other precursors reported for dye removal include sugar industry wastes (Blanco-Castro et al., 2000), coir pith (Namasivayam & Sangeetha, 2006), and coconut shells (Gimba et al., 2009), among other raw lignocellulosic materials.

It is convenient to remark that several fruits and crops have been considered as effective precursors for preparation of adsorbents for dye removal. Specifically, Elizalde-González et al. (2007) reported the adsorption of several basic, acid and reactive dyes from aqueous solutions by avocado activated carbons impregnated with H3PO4. In other study, Elizalde-Gonzalez & Hernandez-Montoya (2008) reported the removal of anthraquinone dyes (i.e., acid blue 80 and acid green 27) using activated carbons obtained from seeds of mango, guava and orange. These fruits are abundant and are considered as a low cost agricultural waste in México and other countries (Elizalde-González & Hernández-Montoya, 2009). These studies indicated that the acid activated carbon obtained from orange seed was the most effective for the removal of acid green 27 from water despite its negligible specific surface; while the activated carbons obtained from mango seed were more effective for the removal of acid blue 80. Authors concluded that the interaction between the functional groups of activated carbons and these dyes are very important in the adsorption process. In other study, guava seed was used as precursor of activated carbon for the removal of Acid orange 7 (AO7), which is a dye commonly used in tanneries, paper manufacturing and textile industry (Elizalde-Gónzalez & Hernández-Montoya, 2009). The optimal conditions for the preparation of guava seed carbon for dye removal were identified using a Taguchi experimental design. Recently, Bello-Huitle et al. (2010) reported the removal of methylene blue dye from water using activated carbons obtained from pecan and castile nutshells. Both pecan and castile nutshells are important crops from México and other countries. In this study, H3PO4 was used as activating agent for these precursors. Adsorption studies indicated that the adsorption capacity of activated carbon obtained from pecan nutshells was higher than that obtained for castile nutshells. Finally, Hernández-Montoya et al. (2011) have reported the preparation of activated carbons for adsorption of acid blue 25 using both pecan nut shells and a calcium solution extracted from egg shell wastes. This adsorbent showed adsorption capacities up to 48 mg/g.

With respect to precursors obtained from plant wastes, El-Ashtoukhy (2009) used the *Loofa egyptiaca* plant to prepare a low-cost activated carbon for the removal of direct blue 106. This plant is cultivated only in Egypt and is a highly branched, fibrous and interconnected cellulosic material. In this study, the adsorbents were obtained from the carbonization of

obtained from oak cups pulp using ZnCl2 have higher phenol adsorption capacities than those obtained for activated carbons produced with H3PO4. They suggested that this best performance was related to the lower amount of acidic surface groups on activated carbon.

Lignocellulosic Materials for the Wastewater Treatment 67

Coir pith ZnCl2 700 Phenol Namasivayam & Sangeetha

Kenaf CO2, HNO3 700 Phenol Nabais et al. (2009)

Rapessed CO2, HNO3 700 Phenol Nabais et al. (2009)

H3PO4 500 Phenol Bello-Huitle et al. (2010)

H3PO4 500 Phenol Bello-Huitle et al. (2010)

p-nitrophenol

p-nitrophenol

H2SO4, CO2 600 – 800 p-nitrophenol Cuerda-Correa et al. (2006)

4-chlorophenol p-cresol, phenol

Table 7. Synthesis conditions of activated carbons obtained from lignocellulosic precursors

Finally, it is important to note that the adsorption of other phenol-based organic compounds on different types of activated carbons has been also studied and they include, for example, the removal of p-nitrophenol using activated carbons obtained from cedar wood activated by H2SO4 (Cuerda-Correa et al., 2006), carbons from almond shell and vine shoot precursors activated with carbon dioxide and oxidized with nitric acid (Mourao et al., 2011), the adsorption of phenol-compounds using coir pith activated carbons (Namasivayam & Sangeetha, 2006), or the removal of 2,4-dichloropenol, 4-chloropenol and p-cresol using KOH and steam-activated carbons obtained from Fir wood (Wu et al., 2005). Overall, these

*Conditions Precursor Pollutant pH T, °C qmax, mg/g Reference*  Almond shell Phenol 3 25 76 – 139 Mourao et al. (2011) Castile nutshells Phenol 7 20 53.2 Bello-Huitle et al. (2010) Kenaf Phenol 7.5 25 45 – 80 Nabais et al. (2009) Pecan nutshells Phenol 7 20 158.7 Bello-Huitle et al. (2010) Rapeseed Phenol 7.5 25 45 – 80 Nabais et al. (2009) Vine shoot Phenol 3 25 73 Mourao et al. (2011) Almond shell p-nitrophenol 3 25 154 – 224 Mourao et al. (2011) Vine shoot p-nitrophenol 3 25 126 – 238 Mourao et al. (2011) Table 8. Adsorption capacities of selected activated carbons obtained from lignocellulosic

600 Phenol Timur et al. (2010)

*Pollutant Reference* 

(2006)

Mourao et al. (2011)

Mourao et al. (2011)

Wu et al. (2005)

*Carbonization temperature, ºC* 

*Precursor Activating* 

Castile nutshells

Oak cups pulp

Pecan nutshells

Almond shell

Cedar wood

*agent* 

Applications of Activated Carbons Obtained from

H3PO4, ZnCl2

for removal of phenol compounds.

Vine shoot CO2, HNO3 800 Phenol

CO2, HNO3 800 Phenol

Fit wood H2O, KOH 780, 900 2,4 dichlorophenol

precursors for removal of phenol compounds from water.

this plant at 500 °C using H3PO4, HNO3 and ZnCl2 as activating agents. Adsorption kinetics and equilibrium studies were performed at 25 °C and different conditions of pH. Results showed that the maximum adsorption was obtained at pH 2. On the other hand, the sea plant *P. Occeanica* (*L*) can be also used as carbon precursor for methylene blue adsorption (Dural et al., 2011). In particular, kinetic and equilibrium adsorption studies of this dye were performed using an activated carbon obtained from this plant activated with ZnCl2. Carbon samples showed adsorption capacities up to 280 mg/g at tested conditions.

Usually, the dye adsorption appears to be higher using activated carbons obtained from ZnCl2 and H3PO4 activation. Adsorption capacities of lignocellulosic-based activated carbons may range from 50 to 400 mg/g. For illustration, dye adsorption capacities for selected activated carbons are reported in Table 6.


Table 6. Adsorption capacities of selected activated carbons obtained from lignocellulosic precursors for dye removal from water.

#### **2.2.3 Phenol compounds**

Phenol and its derivatives are common pollutants present in a variety of effluents from plastic, gasoline, disinfectant, pesticides, pharmaceutical, and steel industries (Lin et al., 2009; Timur et al., 2010). In particular, phenol is an important toxic compound listed as a priority pollutant by the EPA and other environmental protection agencies because of its high toxicity and possible accumulation in the environment. This compound is considered toxic to human beings and, as a consequence, it must be removed before the discharge of wastewaters. Until now, different adsorbents have been reported for the removal of phenol and its derivative compounds, see Table 7.

Specifically, batch experiments for phenol adsorption were performed using microporous activated carbons obtained from both kenaf and rapeseed precursors (Nabais et al., 2009). In particular, the phenol adsorption capacities of both adsorbents were higher than 70 mg/g. In other study, Alam et al. (2009) studied the effect of different synthesis conditions of activated carbon obtained from oil palm empty fruit bunches on phenol removal. These parameters include temperature, activation time and CO2 flow rate. In general, these carbons showed phenol adsorption capacities from 1.03 to 4.83 mg/g. Recently, Bello-Huitle et al. (2010) studied the removal of phenol using activated carbons obtained by chemical activation and pyrolysis of pecan and castile nutshells. These authors synthesized different samples of activated carbons using these crops and adsorption isotherms were performed at 20 °C and pH 7. This study indicated that the activated carbon from pecan nutshells showed better phenol uptakes. On the other hand, Timur et al. (2010) reported that activated carbons

66 Characterization Techniques and Applications in the Wastewater Treatment

this plant at 500 °C using H3PO4, HNO3 and ZnCl2 as activating agents. Adsorption kinetics and equilibrium studies were performed at 25 °C and different conditions of pH. Results showed that the maximum adsorption was obtained at pH 2. On the other hand, the sea plant *P. Occeanica* (*L*) can be also used as carbon precursor for methylene blue adsorption (Dural et al., 2011). In particular, kinetic and equilibrium adsorption studies of this dye were performed using an activated carbon obtained from this plant activated with ZnCl2. Carbon

Usually, the dye adsorption appears to be higher using activated carbons obtained from ZnCl2 and H3PO4 activation. Adsorption capacities of lignocellulosic-based activated carbons may range from 50 to 400 mg/g. For illustration, dye adsorption capacities for

Direct blue 106 2 – 9 25 63.3 – 73.5 El-Ashtoukhy (2009)

Methylene blue 7 20 169.5 Bello-Huitle et al. (2010)

(2011)

*Conditions Precursor Pollutant pH T, °C qmax, mg/g Reference* 

Pecan nutshells Methylene blue 7 20 400 Bello-Huitle et al. (2010) Pecan nut Acid blue 25 6 30 48 Hernández-Montoya et al.

Table 6. Adsorption capacities of selected activated carbons obtained from lignocellulosic

Phenol and its derivatives are common pollutants present in a variety of effluents from plastic, gasoline, disinfectant, pesticides, pharmaceutical, and steel industries (Lin et al., 2009; Timur et al., 2010). In particular, phenol is an important toxic compound listed as a priority pollutant by the EPA and other environmental protection agencies because of its high toxicity and possible accumulation in the environment. This compound is considered toxic to human beings and, as a consequence, it must be removed before the discharge of wastewaters. Until now, different adsorbents have been reported for the removal of phenol

Specifically, batch experiments for phenol adsorption were performed using microporous activated carbons obtained from both kenaf and rapeseed precursors (Nabais et al., 2009). In particular, the phenol adsorption capacities of both adsorbents were higher than 70 mg/g. In other study, Alam et al. (2009) studied the effect of different synthesis conditions of activated carbon obtained from oil palm empty fruit bunches on phenol removal. These parameters include temperature, activation time and CO2 flow rate. In general, these carbons showed phenol adsorption capacities from 1.03 to 4.83 mg/g. Recently, Bello-Huitle et al. (2010) studied the removal of phenol using activated carbons obtained by chemical activation and pyrolysis of pecan and castile nutshells. These authors synthesized different samples of activated carbons using these crops and adsorption isotherms were performed at 20 °C and pH 7. This study indicated that the activated carbon from pecan nutshells showed better phenol uptakes. On the other hand, Timur et al. (2010) reported that activated carbons

samples showed adsorption capacities up to 280 mg/g at tested conditions.

selected activated carbons are reported in Table 6.

precursors for dye removal from water.

and its derivative compounds, see Table 7.

**2.2.3 Phenol compounds** 

*Loofa egyptiaca*  plant

Castile nutshells obtained from oak cups pulp using ZnCl2 have higher phenol adsorption capacities than those obtained for activated carbons produced with H3PO4. They suggested that this best performance was related to the lower amount of acidic surface groups on activated carbon.


Table 7. Synthesis conditions of activated carbons obtained from lignocellulosic precursors for removal of phenol compounds.


Table 8. Adsorption capacities of selected activated carbons obtained from lignocellulosic precursors for removal of phenol compounds from water.

Finally, it is important to note that the adsorption of other phenol-based organic compounds on different types of activated carbons has been also studied and they include, for example, the removal of p-nitrophenol using activated carbons obtained from cedar wood activated by H2SO4 (Cuerda-Correa et al., 2006), carbons from almond shell and vine shoot precursors activated with carbon dioxide and oxidized with nitric acid (Mourao et al., 2011), the adsorption of phenol-compounds using coir pith activated carbons (Namasivayam & Sangeetha, 2006), or the removal of 2,4-dichloropenol, 4-chloropenol and p-cresol using KOH and steam-activated carbons obtained from Fir wood (Wu et al., 2005). Overall, these

Recently, the performance of activated carbon has been studied and tested in the removal of new environmental pollutants originated from consumer products and by-products used in industrial, agricultural and other human activities. In particular, these emergent pollutants include pesticides, household-cleaning chemicals, fragrances, and disinfectants, among other organic and inorganic toxic compounds (Cabrita et al., 2010). Based on this perspective, it is expected that the applications of activated carbons obtained from lignocellulosic precursors will increase for wastewater treatment in forthcoming years.

Lignocellulosic Materials for the Wastewater Treatment 69

The surface chemistry of activated carbons plays an important role to determine their adsorption performance in wastewater treatment. In particular, the precursor has a critical effect on the surface chemistry properties of activated carbons (Wang et al., 2011). The presence of several functional groups on carbon surface (e.g., carboxylic, carbonyl, hydroxyl, ether, quinine, lactone, anhydride) implies the presence of many types of pollutant-carbon interactions (Wu et al., 2005). It is important to remark that the nature and prevalence of

Several studies have shown that the surface functional groups of activated carbons play an important role for the adsorption of a specific pollutant (Ould-Idriss et al., 2011). For example, polar or acidic oxygen functional groups on the surface of activated carbons have been recognized to play a fundamental role on metal adsorption (Basso et al., 2002). In fact, reported studies have shown the predominant influence of surface oxygen functional groups of activated carbons on metal uptake (Basso et al., 2002). For this application, the following trend has been identified: the higher the content of functional groups, the greater the adsorption extent of the activated carbon. These functional groups include: carbonyls, phenols, lactones and carboxylic acids (Basso et al., 2002). Also, activated carbons with sulfur functional groups are suitable for the removal of some heavy metals such as cadmium (Tajar et al., 2009). In the case of phenol and its derivatives compounds, the adsorption process is also related to the oxygen-containing surface functional groups (Tamir et al., 2010). Literature indicates that the most relevant heteroatoms for phenol adsorption are

On the other hand, cation-exchange mechanisms are also involved in the adsorption of some pollutants from water. Some studies have suggested that the cation-exchange properties of activated carbons are determined by the presence of oxygen- and phosphorous-containing surface groups. For example, Dastgheib & Rockstraw (2001) reported that an ion-exchange and surface complexation with oxygen- and phosphorus-containing groups on pecan shell activated carbon may be involved in the adsorption of copper from water. This cation exchange capacity of activated carbons can be improved via chemical activation (Puziy et al., 2007). Usually, activated carbons obtained from carbonization and phosphoric acid

Electrostatic interactions appear to play a key role in the adsorption mechanism of some pollutants including metals ions and dyes (Wang et al., 2011). For the case of some dyes, the

functional groups on carbon surface may be modified by activation methods.

**3. Description of adsorption mechanisms** 

Applications of Activated Carbons Obtained from

nitrogen and oxygen (Nabais et al., 2009).

activation may show a considerable cation exchange capacity.

**of priority water pollutants using activated carbons** 

activated carbons showed adsorption capacities from 40 to 200 mg/g. Table 8 shows the adsorption capacities of different activated carbons used for removal of phenol compounds.

#### **2.2.4 Other organic and inorganic toxic pollutants**

Activated carbons can be used for the removal of other organic and inorganic compounds such as nitrates, thyocyanate, selenite, vanadium, sulfates, molybdate, fluorides, and pharmaceuticals, among other pollutants (Namasivayam & Sangeetha, 2006).

Drinking water sources in a number of developing and underdeveloped countries is polluted by toxic anions such as fluorides. Specifically, the presence of high fluoride concentrations in drinking water is a common problem in several countries including México, China and India (Alagumuthu & Rajan, 2010; Hernández-Montoya et al., 2011). Fluoride concentrations in drinking water higher than 1.5 mg/L is the principal cause of dental fluorosis in children and may cause bone fluorosis if a chronic exposure occurs. Traditional lignocellulosic precursors and activation procedures are not suitable for the production of activated carbons suitable for fluoride removal from water. However, some studies have shown that fluoride ion has a strong affinity towards multivalent metal ions, e.g., Al3+, Fe3+ and Zr4+ (Alagumuthu & Rajan, 2010) and also may interact with some bivalent ions such as calcium (Hernández-Montoya et al., 2011). Based on this fact, some studies have reported the application of non-conventional impregnating agents for the preparation of activated carbons for fluoride removal from water. For example, Alagumuthu & Rajan (2010) studied the carbonization of cashew nut shell impregnated with zirconium oxy chloride. Cashew nut is one of the commercialized products of the cashew tree and the cashew nut shell is the waste product of cashew nut, which contains potassium and magnesium compounds. In general, adsorption capacities of this carbon were around 2.0 mg/g at tested conditions. These authors indicated that the fluoride adsorption was related to both electrostatic interactions and a chemisorption mechanism that involves chloride and hydroxide species of this carbon. In particular, the presence of zirconium species improves the adsorption properties of this adsorbent. A recent study showed that activated carbons obtained from pecan nut shells and egg shell wastes can be used for fluoride removal from water (Hernández-Montoya et al., 2012). This study concluded that the calcium chemical species on the carbon surface played an important role in the fluoride adsorption process.

On the other hand, activated carbons have been used for the removal of pharmaceuticals from water (e.g., Cabrita et al., 2010). Several pharmaceuticals are released to the environment via human and animal excreta and, as a consequence, trace quantities of these pollutants tend to accumulate in water resources. Cabrita et al. (2010) reported the removal of acetaminophen (i.e., paracetamol) from aqueous solution using an activated carbon from peach stones. This activated carbon is characterized by a high amount of oxygen functionalities, which appear to be related to the presence of pyrone and/or chromene-like type structures. This carbon showed an adsorption capacity higher than those obtained for activated carbon synthesized from plastic waste and commercial carbons. This study concluded that the adsorption of this pharmaceutical is a complex process that depends on both the chemical composition and the textural parameters of activated carbon.

68 Characterization Techniques and Applications in the Wastewater Treatment

activated carbons showed adsorption capacities from 40 to 200 mg/g. Table 8 shows the adsorption capacities of different activated carbons used for removal of phenol compounds.

Activated carbons can be used for the removal of other organic and inorganic compounds such as nitrates, thyocyanate, selenite, vanadium, sulfates, molybdate, fluorides, and

Drinking water sources in a number of developing and underdeveloped countries is polluted by toxic anions such as fluorides. Specifically, the presence of high fluoride concentrations in drinking water is a common problem in several countries including México, China and India (Alagumuthu & Rajan, 2010; Hernández-Montoya et al., 2011). Fluoride concentrations in drinking water higher than 1.5 mg/L is the principal cause of dental fluorosis in children and may cause bone fluorosis if a chronic exposure occurs. Traditional lignocellulosic precursors and activation procedures are not suitable for the production of activated carbons suitable for fluoride removal from water. However, some studies have shown that fluoride ion has a strong affinity towards multivalent metal ions, e.g., Al3+, Fe3+ and Zr4+ (Alagumuthu & Rajan, 2010) and also may interact with some bivalent ions such as calcium (Hernández-Montoya et al., 2011). Based on this fact, some studies have reported the application of non-conventional impregnating agents for the preparation of activated carbons for fluoride removal from water. For example, Alagumuthu & Rajan (2010) studied the carbonization of cashew nut shell impregnated with zirconium oxy chloride. Cashew nut is one of the commercialized products of the cashew tree and the cashew nut shell is the waste product of cashew nut, which contains potassium and magnesium compounds. In general, adsorption capacities of this carbon were around 2.0 mg/g at tested conditions. These authors indicated that the fluoride adsorption was related to both electrostatic interactions and a chemisorption mechanism that involves chloride and hydroxide species of this carbon. In particular, the presence of zirconium species improves the adsorption properties of this adsorbent. A recent study showed that activated carbons obtained from pecan nut shells and egg shell wastes can be used for fluoride removal from water (Hernández-Montoya et al., 2012). This study concluded that the calcium chemical species on the carbon surface played an important role in the fluoride

On the other hand, activated carbons have been used for the removal of pharmaceuticals from water (e.g., Cabrita et al., 2010). Several pharmaceuticals are released to the environment via human and animal excreta and, as a consequence, trace quantities of these pollutants tend to accumulate in water resources. Cabrita et al. (2010) reported the removal of acetaminophen (i.e., paracetamol) from aqueous solution using an activated carbon from peach stones. This activated carbon is characterized by a high amount of oxygen functionalities, which appear to be related to the presence of pyrone and/or chromene-like type structures. This carbon showed an adsorption capacity higher than those obtained for activated carbon synthesized from plastic waste and commercial carbons. This study concluded that the adsorption of this pharmaceutical is a complex process that depends on

both the chemical composition and the textural parameters of activated carbon.

pharmaceuticals, among other pollutants (Namasivayam & Sangeetha, 2006).

**2.2.4 Other organic and inorganic toxic pollutants** 

be

adsorption process.

Recently, the performance of activated carbon has been studied and tested in the removal of new environmental pollutants originated from consumer products and by-products used in industrial, agricultural and other human activities. In particular, these emergent pollutants include pesticides, household-cleaning chemicals, fragrances, and disinfectants, among other organic and inorganic toxic compounds (Cabrita et al., 2010). Based on this perspective, it is expected that the applications of activated carbons obtained from lignocellulosic precursors will increase for wastewater treatment in forthcoming years.

#### **3. Description of adsorption mechanisms of priority water pollutants using activated carbons**

The surface chemistry of activated carbons plays an important role to determine their adsorption performance in wastewater treatment. In particular, the precursor has a critical effect on the surface chemistry properties of activated carbons (Wang et al., 2011). The presence of several functional groups on carbon surface (e.g., carboxylic, carbonyl, hydroxyl, ether, quinine, lactone, anhydride) implies the presence of many types of pollutant-carbon interactions (Wu et al., 2005). It is important to remark that the nature and prevalence of functional groups on carbon surface may be modified by activation methods. 

Several studies have shown that the surface functional groups of activated carbons play an important role for the adsorption of a specific pollutant (Ould-Idriss et al., 2011). For example, polar or acidic oxygen functional groups on the surface of activated carbons have been recognized to play a fundamental role on metal adsorption (Basso et al., 2002). In fact, reported studies have shown the predominant influence of surface oxygen functional groups of activated carbons on metal uptake (Basso et al., 2002). For this application, the following trend has been identified: the higher the content of functional groups, the greater the adsorption extent of the activated carbon. These functional groups include: carbonyls, phenols, lactones and carboxylic acids (Basso et al., 2002). Also, activated carbons with sulfur functional groups are suitable for the removal of some heavy metals such as cadmium (Tajar et al., 2009). In the case of phenol and its derivatives compounds, the adsorption process is also related to the oxygen-containing surface functional groups (Tamir et al., 2010). Literature indicates that the most relevant heteroatoms for phenol adsorption are nitrogen and oxygen (Nabais et al., 2009).

On the other hand, cation-exchange mechanisms are also involved in the adsorption of some pollutants from water. Some studies have suggested that the cation-exchange properties of activated carbons are determined by the presence of oxygen- and phosphorous-containing surface groups. For example, Dastgheib & Rockstraw (2001) reported that an ion-exchange and surface complexation with oxygen- and phosphorus-containing groups on pecan shell activated carbon may be involved in the adsorption of copper from water. This cation exchange capacity of activated carbons can be improved via chemical activation (Puziy et al., 2007). Usually, activated carbons obtained from carbonization and phosphoric acid activation may show a considerable cation exchange capacity.

Electrostatic interactions appear to play a key role in the adsorption mechanism of some pollutants including metals ions and dyes (Wang et al., 2011). For the case of some dyes, the

carbon (Alagumuthu & Rajan, 2010). These authors reported that NaOH was more effective for carbon regeneration and may recovery more than 95% of fluoride loaded on activated

Lignocellulosic Materials for the Wastewater Treatment 71

In summary, a limited number of studies have been reported for the regeneration of activated carbons used for wastewater treatment. Therefore, further research should be performed to develop low-cost and effective regeneration procedures for activated carbons

This chapter describes the application of lignocellulosic precursors for the synthesis of activated carbons used in the removal of different pollutants from drinking water and wastewaters. In particular, lignocellulosic precursors can be used for the synthesis of activated carbons with attractive properties for the adsorption of different organic and inorganic pollutants. Literature indicates that we can prepare activated carbons with improved adsorption properties to remove effectively priority water pollutants by using the appropriate lignocellulosic precursors and by optimizing the conditions of carbonization and activation. In particular, research on activated carbon for wastewater treatment should give special attention in the optimization of synthesis conditions for improving adsorption properties to remove hazardous pollutants such as fluoride and arsenic. Also, the development of low-cost regeneration procedures is highlighted to reduce the costs of water treatment technologies. Finally, it is expected that the applications of activated carbons obtained from these precursors will increase for wastewater treatment and other science

Authors acknowledge the financial support provided by CONACYT, DGEST and Instituto

[1] Ahmad, A.A. & Hameed, B.H. (2010). Fixed-bed adsorption of reactive azo dye onto granular activated carbon prepared from waste. *Journal of Hazardous Materials*, Vol. 175,

[2] Alagumuthu, G. & Rajan M. (2010). Equilibrium and kinetics of adsorption of fluoride onto zirconium impregnated cashew nut shell carbon. *Chemical Engineering Journal*, Vol.

[3] Alam, M.Z., Ameem, E.S., Muyibi, S.A. & Kabbashi, N.A. (2009). The factors affecting the performance of activated carbon prepared from oil palm empty fruit bunches for adsorption of phenol. *Chemical Engineering Journal*, Vol. 155, No. 1-2, (February 2011),

[4] Álvarez, P., Blanco, C. & Granda, M. (2007). The adsorption of chromium (VI) from industrial wastewater by acid and base-activated lignocellulosic residues. *Journal of* 

*Hazardous Materials*, Vol. 144, No. 1-2, (June 2007), pp. (400-405), ISSN 0304-3894.

carbon.

used in water purification.

Applications of Activated Carbons Obtained from

fields in forthcoming years.

**6. Acknowledgments** 

**7. References** 

Tecnológico de Aguascalientes (México).

pp. (191-198), ISSN 1385-8947.

No. 1-3 (March 2010), pp. (298–303), ISSN 0304-3894.

158, No. 3 (April 2010), pp. (451-457), ISSN 1385-8947.

**5. Conclusions** 

adsorption process has been related to electrostatic force of attraction between dyes and activated carbon and also to complex formation (Tamir et al., 2010). In general, literature indicates that dye removal using activated carbons may imply several mechanisms including ion-dipole forces, ion exchange, hydrogen bonding and non-specific interactions. Also, phenol adsorption onto activated carbon may occur via a complex interplay of electrostatic and dispersion interactions (Nabais et al., 2009).

It is convenient to recall that the adsorption process using activated carbon depends on the operating conditions of removal process (i.e., adsorbent mass, pollutant concentration, operating mode), the adsorbent characteristics (e.g., functional groups, textural properties, etc.) and the solution chemistry (e.g., temperature, pH, ionic strength). Based on this fact, diverse adsorption mechanisms may occur simultaneously during the removal of a specific pollutant using activated carbons synthesized from lignocellulosic precursors. Therefore, the identification and characterization of adsorption mechanisms involved in the removal of priority water pollutants is a relevant and important research topic for understanding the chemistry of activated carbons.

#### **4. Desorption and regeneration studies of activated carbons used in water treatment**

Adsorbent regeneration is an important operating parameter to establish the feasibility and the operating costs of water treatment processes using activated carbons. The performance and efficacy of desorbing agents depends on the carbon type, the concentration of sorbed pollutant, and the operating conditions of desorption process (e.g., concentration of desorbing agent, temperature and sorbent dosage).

In general, literature indicates that some regeneration studies have been performed using activated carbons obtained from lignocellulosic precursors loaded with some waster pollutants especially heavy metal ions. Specifically, copper desorption from pecan shell activated carbon has been studied using both water and 10% HCl solution (Dastgheib & Rockstraw, 2001). This study showed that copper desorption with water is not feasible, while HCl may recovery up to 98% of the copper adsorbed on pecan shell activated carbon. Basso et al. (2002) performed desorption studies to recovery cadmium and nickel ions adsorbed on activated carbons obtained from *Arundo donax* plant canes using HCl. This study concluded that it is feasible to recovery the 90% of the metal ions loaded in these activated carbons. In other study, Tajar et al. (2009) reported preliminary results for desorption of cadmium from an activated carbon obtained from nutshells using HCl, HNO3 and H2SO4 as extractants. It appears that HCl is an effective chemical for desorbing cadmium ions from this activated carbon. Authors concluded that H+ ions from HCl displace cadmium ions bounded to the activated carbon during the desorption stage. Recently, the chromium desorption from activated carbon obtained from *Pinus sylvestris* sawdust has been studied using H2SO4 (Álvarez et al., 2007). Results of carbon regeneration showed that this activated carbon retains its chromium adsorption capacity during the first regeneration cycle. However, the adsorption performance of this adsorbent is substantially reduced in subsequent regeneration cycles. With respect to other pollutants, HCl and NaOH have been used for the fluoride desorption using a zirconium impregnated cashew nut shell shell

carbon (Alagumuthu & Rajan, 2010). These authors reported that NaOH was more effective for carbon regeneration and may recovery more than 95% of fluoride loaded on activated carbon.

In summary, a limited number of studies have been reported for the regeneration of activated carbons used for wastewater treatment. Therefore, further research should be performed to develop low-cost and effective regeneration procedures for activated carbons used in water purification.

#### **5. Conclusions**

Lignocellulosic Precursors Used in the Synthesis of Activated Carbon-

70 Characterization Techniques and Applications in the Wastewater Treatment

adsorption process has been related to electrostatic force of attraction between dyes and activated carbon and also to complex formation (Tamir et al., 2010). In general, literature indicates that dye removal using activated carbons may imply several mechanisms including ion-dipole forces, ion exchange, hydrogen bonding and non-specific interactions. Also, phenol adsorption onto activated carbon may occur via a complex interplay of

It is convenient to recall that the adsorption process using activated carbon depends on the operating conditions of removal process (i.e., adsorbent mass, pollutant concentration, operating mode), the adsorbent characteristics (e.g., functional groups, textural properties, etc.) and the solution chemistry (e.g., temperature, pH, ionic strength). Based on this fact, diverse adsorption mechanisms may occur simultaneously during the removal of a specific pollutant using activated carbons synthesized from lignocellulosic precursors. Therefore, the identification and characterization of adsorption mechanisms involved in the removal of priority water pollutants is a relevant and important research topic for understanding the

Adsorbent regeneration is an important operating parameter to establish the feasibility and the operating costs of water treatment processes using activated carbons. The performance and efficacy of desorbing agents depends on the carbon type, the concentration of sorbed pollutant, and the operating conditions of desorption process (e.g., concentration of

In general, literature indicates that some regeneration studies have been performed using activated carbons obtained from lignocellulosic precursors loaded with some waster pollutants especially heavy metal ions. Specifically, copper desorption from pecan shell activated carbon has been studied using both water and 10% HCl solution (Dastgheib & Rockstraw, 2001). This study showed that copper desorption with water is not feasible, while HCl may recovery up to 98% of the copper adsorbed on pecan shell activated carbon. Basso et al. (2002) performed desorption studies to recovery cadmium and nickel ions adsorbed on activated carbons obtained from *Arundo donax* plant canes using HCl. This study concluded that it is feasible to recovery the 90% of the metal ions loaded in these activated carbons. In other study, Tajar et al. (2009) reported preliminary results for desorption of cadmium from an activated carbon obtained from nutshells using HCl, HNO3 and H2SO4 as extractants. It appears that HCl is an effective chemical for desorbing cadmium ions from this activated carbon. Authors concluded that H+ ions from HCl displace cadmium ions bounded to the activated carbon during the desorption stage. Recently, the chromium desorption from activated carbon obtained from *Pinus sylvestris* sawdust has been studied using H2SO4 (Álvarez et al., 2007). Results of carbon regeneration showed that this activated carbon retains its chromium adsorption capacity during the first regeneration cycle. However, the adsorption performance of this adsorbent is substantially reduced in subsequent regeneration cycles. With respect to other pollutants, HCl and NaOH have been used for the fluoride desorption using a zirconium impregnated cashew nut shell

electrostatic and dispersion interactions (Nabais et al., 2009).

chemistry of activated carbons.

**4. Desorption and regeneration studies of activated carbons used in water treatment**

desorbing agent, temperature and sorbent dosage).

This chapter describes the application of lignocellulosic precursors for the synthesis of activated carbons used in the removal of different pollutants from drinking water and wastewaters. In particular, lignocellulosic precursors can be used for the synthesis of activated carbons with attractive properties for the adsorption of different organic and inorganic pollutants. Literature indicates that we can prepare activated carbons with improved adsorption properties to remove effectively priority water pollutants by using the appropriate lignocellulosic precursors and by optimizing the conditions of carbonization and activation. In particular, research on activated carbon for wastewater treatment should give special attention in the optimization of synthesis conditions for improving adsorption properties to remove hazardous pollutants such as fluoride and arsenic. Also, the development of low-cost regeneration procedures is highlighted to reduce the costs of water treatment technologies. Finally, it is expected that the applications of activated carbons obtained from these precursors will increase for wastewater treatment and other science fields in forthcoming years. recovery affecting

#### **6. Acknowledgments**

Authors acknowledge the financial support provided by CONACYT, DGEST and Instituto Tecnológico de Aguascalientes (México).

#### **7. References**


[18] Dural, M.U., Cavas, L., Papageorgious, S.K. & Katsaros, F.K. (2011). Methylene blue adsorption on activated carbon prepared from *Posidonia oceánica (L)* dead leaves: kinetics and equilibrium studies. *Chemical Engineering Journal*, Vol. 168, No. 1, (March

Lignocellulosic Materials for the Wastewater Treatment 73

[19] El Ashtoukhy E.S.Z. (2009). Loofa egyptiaca as a novel adsorbent for removal of direct blue dye from aqueous solution. *Journal of Environmental Management,* Vol. 90, No. 8,

[20] El-Hendawy, A.N.A. (2009). An insight into the KOH activation mechanism through the production of microporous activated carbon for the removal of Pb2+ cations. *Applied* 

[22] Elizalde-González, M.P. & Hernández-Montoya, V. (2008). Fruit seeds as adsorbents and precursors of carbon for the removal of anthraquinone dyes. *International Journal of* 

[23] Elizalde-González, M.P. & Hernández-Montoya, V. (2009). Removal of acid orange 7 by guava seed carbon: A four parameter optimization study. *Journal of Hazardous Materials*,

[24] Elizalde-González, M.P. & Hernández-Montoya, V. (2009). Guava seed as an adsorbent and as a precursor of carbon for the adsorption of acid dyes. *Bioresource Technology*, Vol.

[25] Gimba, C.E., Turoti, M., Egwaikhide, P.A. & Akporhonor, E.E. (2009). Adsorption of indigo blue dye and some toxic metals by activated carbons from coconut shells. *Electronic Jorunal of Environmental, Agricultural and Food Chemistry*, Vol. 8, No. 11, pp.

[26] Giraldo, L. & Moreno-Piraján, J.C. (2008). Pb2+ adsorption from aqueous solutions on activated carbons obtained from lignocellulosic residues. *Brazilian Journal of Chemical* 

[27] Haro, M., Ruiz, B., Andrade, M., Mestre, A.S., Parra, J.B., Carvalho, A.P. & Ania, C.O. (2011). Dual role of copper on the reactivity of activated carbons from coal and lignocellulosic precursors. *Microporous and Mesoporous Materials*, In press, ISSN 1387-1811. [28] Hernández-Montoya, V., Mendoza-Castillo, D.I., Bonilla-Petriciolet, A., Montes-Morán, M.A. & Pérez-Cruz, M.A. (2011). Role of the pericarp of Carya illinoinensis as biosorbent and as precursor of activated carbon for the removal of lead and acid blue 25 in aqueous solutions. *Journal of Analytical and Applied Pyrolysis*, Vol. 92, No. 1,

[29] Hernández-Montoya, V., Ramírez-Montoya, L.A., Bonilla-Petriciolet, A. & Montes-Moran, M. (2012). Optimizing the removal of fluoride from wáter using new carbons obtained by modification of nut shell with a calcium solution from egg shell. *Biochemical* 

[30] Krishnan, K.A., Sreejalekshmi, K.G. & Varghese, S. (2010). Adsorptive retention of citric acid onto activated carbon prepared from *Havea braziliansis* sawdust: Kinetic and isotherm overview. *Desalination*, Vol. 257, No. 1-3, (July 2010), pp. (46-52), ISSN 0011-

*Engineering*, Vol. 25, No. 1, (January 2008), pp. (143-151), ISSN 0104-6632.

*Chemical Engineering*, Vol. 1, No. 2-3, pp. (243-253), ISSN 0974-5793.

Vol. 168, No. 1, (August 2009), pp. (515-522), ISSN 0304-3894.

100, No. 7, (April 2009), pp. (2111-2117), ISSN 0960-8524.

(September 2011), pp. (143-151), ISSN 0165-2370.

*Engineering Journal,* In press, ISSN 1369-703X.

9164.

*Surface Science,* Vol. 255, No. 6, (January 2009), pp. (3723–3730), ISSN: 0169-4332. [21] Elizalde-González, M.P. Mattusch, J. Peláez-Cid, A.A. & Wennrich, R. (2007). Characterization of adsorbent materials prepared from avocado kernel seeds: natural, activated and carbonized forms. *Journal of Analytical and Applied Pyrolysis*, Vol. 78, No. 1,

2011), pp. (77-85), ISSN 1385-8947.

Applications of Activated Carbons Obtained from

(June 2009), pp. (2755–2761), ISSN 0301-4797.

(January 2007), pp. (185-193), ISSN 0165-2370.

(1194-1201), ISSN 1579-4377.


72 Characterization Techniques and Applications in the Wastewater Treatment

[5] Altenor, S., Carene-Melane, B. & Gaspard, S. (2009). Activated carbons from lignocellulosic waste materials for water treatment: a review. *International Journal of Environmental Technology and Management*, Vol. 10, No. 3-4, pp. (308-326), ISSN 1466-2132. [6] Baccar, R., Bouzid, J., Feki, M. & Montiel A. (2009). Preparation of activated carbon from Tunisian olive-waste cakes and its application for adsorption of heavy metal ions. *Journal of Hazardous Materials*, Vol. 162, No. 2-3, (March 2009), pp. (1522–1529), ISSN 0304-3894. [7] Basso, M.C., Cerrella, E.G. & Cukierman A.K. (2002). Activated carbons developed from rapidly renewable bioresource for removal of cadmium (II) and nickel (II) ions from dilute aqueous solution. *Industrial Engineering Chemical Research*, Vol. 41, No. 2,

[8] Bello-Huitle, V., Atenco-Fernández, P. & Reyes-Mazzoco, R. (2010). Adsorption studies of methylene blue and phenol onto pecan and castile nutshells prepared by chemical activation. *Revista Mexicana de Ingeniería Química*, Vol. 9, No. 3, pp. (313-322), ISSN 1665-2738. [9] Blanco-Castro, J., Bonelli, P., Cerrella E. & Cukierman A.L. (2000). Phosphoric acid activation of agricultural residues and bagasse from sugar cane: influence of the experimental conditions on adsorption characteristics of activated carbons. *Industrial Engineering Chemical Research*, Vol. 39, No. 11, (September 2000), pp. (4166-4172), ISSN

0888-5885.

[10] Cabrita, I., Ruiz, B., Mestre, A.S., Fonseca, I.M., Carvalho, A.P. & Ania C.O. (2010). Removal of an analgesic using activated carbons prepared from urban and industrial residues. *Chemical Engineering Journal*, Vol. 163, No. 3, (October 2010), pp. (249-255),

[11] Chan, L.S., Cheung, W.H. & McKay, G. (2008). Adsorption of acid dyes by bamboo derived activated carbon. *Desalination*, Vol. 218, No. 1-3, (January 2008), pp. (304–312),

[12] Chan, L.S., Cheung, W.H. Allen, S.J. & McKay G. (2009). Separation of acid-dyes mixture by bamboo derived active carbon. *Separation and Purification Technology*, Vol. 67,

[13] Cuerda-Correa, E.M., Díaz-Díez, M.A., Macías-García, A. & Gañán-Gómez, J. (2006). Preparation of activated carbons previously treated with sulfuric acid. A study of their adsorption capacity in solution. *Applied Surface Science,* Vol. 252, No. 17, (June 2006), pp.

[14] Dastgheib, S.A. & Rockstraw, D.A. (2001). Pecan shell activated carbons: synthesis, characterization, and application for the removal of copper from aqueous solution.

[15] de Lima, L.S., Machado-Araujo, M.D., Quináia, S.P., Migliorine, D.W. & Garcia, J.R. (2011). Adsorption modeling of Cr, Cd and Cu on activated carbon of different origins by using fractional factorial design. *Chemical Engineering Journal,* Vol. 166, No. 3,

[16] Demirbas, A. (2009). Agricultural based activated carbons for the removal of dyes from aqueous solutions: A review. *Journal of Hazardous Materials*, Vol. 167, No. 1-3, (August

[17] Dermibas, E., Dizge, N., Sulak, M.T. & Kobya, M. (2009). Adsorption kinetics and equilibrium studies of copper from aqueous solutions using hazelnut shell activated carbon. *Chemical Engineering Journal*, Vol. 148, No. 2-3, (May 2009), pp. (480-487), ISSN

*Carbon*, Vol. 39, No. 12, (October 2001), pp. (1849-1855), ISSN 0008-6223.

(December 2001), pp. (180-189), ISSN 0888-5885.

No. 2, (June 2009), pp. 166-172, ISSN 1383-5866.

(February 2011), pp. (881–889), ISSN 1385-8947.

0888-5885.

ISSN 1385-8947.

ISSN 0011-9164.

(6042-6045), ISSN 0169-4332.

2009), pp. (1-9), ISSN 0304-3894.

1385-8947.


[44] Wang, Z., Nie, E., Li J., Zhao Y., Luo X. & Zheng Z. (2011). Carbons prepared from Spartina alterniflora and its anaerobically digested residue by H3PO4 activation: Characterization and adsorption of cadmium from aqueous solutions. *Journal of* 

Lignocellulosic Materials for the Wastewater Treatment 75

[46] Wu, F.C., Tseng, R.L. & Juang, R.S. (2005). Preparation of highly microporous carbons from fir wood by KOH activation for adsorption of dyes and phenols from water. *Separation and Purification Technology*, Vol. 47, No. 1-2, (December 2005), pp. (10-19),

*Hazardous Materials,* Vol. 188, No. 1-3, (April 2011), pp. (29-36), ISSN 0304-3894. [45] Wojanárovits, L., Földváry, Cs.M. & Takács E. (2010). Radiation-induced grafting of cellulose for adsorption of hazardous water pollutans: A review. *Radiation Physics and* 

*Chemistry*, Vol. 79, No. 8, (August 2010), pp. (848-862), ISSN 0969-806X.

ISSN 1383-5866.

Applications of Activated Carbons Obtained from


74 Characterization Techniques and Applications in the Wastewater Treatment

[31] Mohamed, A. R., Mohammadi, M. & Darzi, G.N. (2010). Preparation of carbon molecular sieve from lignocellulosic biomass: A review. *Renewable and Sustainable* 

[33] Mussatto, S.I., Fernandez, M., Rocha, G.J.M., Orfao, J.J.M., Teixeira J.A. & Roberto, I.C. (2010). Production, characterization and application of activated carbon from brewer's spent grain lignin. *Bioresource Technology*, Vol. 101, No. 7, (April 2010), pp. (2450-2457),

[34] Namasivayam, C. & Sangeetha, D. (2006). Recycling of agricultural solid waste, coir pith: Removal of anions, heavy metals, organics and dyes from water by adsorption onto ZnCl2 activated coir pith carbon. *Journal of Hazardous Materials,* Vol. 135, No. 1-3

[35] Ould-Idriss, A., Stitou, M., Cuerda-Correa, E.M., Fernández-González, C., Macías-García, A., Alexandre-Franco, M.F. & Gómez-Serrano, V. (2011). Preparation of activated carbons from olive-tree Wood revisited. II. Physical activation with air. *Fuel Processing Technology*, Vol. 92, No. 2, (February 2011), pp. (266-270), ISSN 0378-3820. [36] Ozcimen, D. & Ersoy-Mericboyu, A. (2009). Removal of copper from aqueous solutions by adsorption onto chestnut shell and grapeseed activated carbons. *Journal of Hazardous* 

*Materials*, Vol. 168, No. 2-3, (September 2009), pp. (1118-1125), ISSN 0304-3894. [37] Puziy, A.M.; Poddubnaya, O.I.; Martínez-Alonso, A.; Castro-Muñiz, A.; Suárez-García, F. & Tascón, J.M.D. (2007). Oxygen and phosphorus enriched carbons from lignocellulosic material. *Carbon*, Vol. 45, No. 10, (September 2007), pp. (1941-1950), ISSN 0008-6223. [38] Satyanarayan, K.G., Guimaraes, J.L. & Wypych, F. (2007). Studies on lignocellulosic fibers of Brazil. Part I: source, production, morphology, properties and applications.

*Composites: Part A*, Vol. 38, No. 7, (July 2007), pp. (1694-1709), ISSN 1359-835X. [39] Silvestre-Albero, A., Goncalvez, M., Itoh, T., Kaneko, K., Endo, M., Thommes, M., Rodríguez-Reinoso, F. & Silvestre-Albero, J. (2012). Well-defined mesoporosity on lignocellulosic-derived activated carbons. *Carbon*, Vol. 50, No. 1, (January 2012), pp. (66-

[40] Sreejalekshmi, K.G., Anoop-Krishnan, K. & Anirudhan, T.S. (2009). Adsorption of Pb(II) and Pb(II)-citric acid on sawdust activated carbon: kinetic and equilibrium isotherm studies. *Journal of Hazardous Materials*, Vol. 161, No. 2-3, (January 2009), pp. (1506-1513),

[41] Tajar, A.F., Kaghazchi, T. & Soleimani, M. (2009). Adsorption of cadmium from aqueous solutions on sulfurized activated carbon prepared from nut shells. *Journal of Hazardous* 

[42] Timur, S., Kantarli, I.C., Onenc, S. & Yanik, J. (2010). Characterization and application of activated carbon produced from oak cups pulp. *Journal of Analytical and Applied* 

[43] Valente Nabis, J.M., Gomez, J.A., Suhas, Carrott, P.J.M., Laginhas, C. & Roman, S. (2009). Phenol removal onto novel activated carbons made from lignocellulosic precursors: influence of surface properties. *Journal of Hazardous Materials*, Vol. 167, No.

*Materials*, Vol. 165, No. 1-3, (June 2009), pp. (1159-1164), ISSN 0304-3894.

*Pyrolysis*, Vol. 89, No. 1, (September 2010), pp. (129-136), ISSN 0165-2370.

1-3, (August 2009), pp. (904-910), ISSN 0304-3894.

*Energy Reviews,* Vol. 14, No. 6, (August 2010), pp. (1591-1599), ISSN 1364-0321. [32] Mourao, P.A.M., Laginhas, C., Custodio, F., Nabais, J.M.V., Carrot, P.J.M. & Ribeiro Carrott, M.M.L. (2011). Influence of oxidation process on the adsorption capacity of activated carbon from lignocellulosic precursors. *Fuel Processing Technology*, Vol. 92, No.

2, (February 2011), pp. (241-246), ISSN 0378-3820.

(July 2006), pp. (449–452), ISSN 0304-3894.

ISSN 0960-8524.

72), ISSN 0008-6223.

ISSN 0304-3894.


**5** 

*México* 

**Characterization of Pyrolysis Products** 

Nowadays, energy security and sustainable development are two major challenges encountered by the world. Renewable energy should be studied extensively to explore new technologies and in order to maintain secure energy sources for sustainable development, considering the fact that the energy demand is increasing, depleting fossil fuel reserves, with

Biomass is one of the most important renewable energy sources and is considered an alternative to fossil fuels. Biomass thermo chemical conversion processes including pyrolysis, combustion, gasification and liquefaction are employed for power generation and production of liquid biofuels, chemicals and charcoal, which can be used as activated carbon. Biomass is mainly composed of carbon; recently this property has been very attractive for the purpose of producing functional carbon materials, which have relevant

Biomass resources include wood from plantation forests, residues from agricultural or forest production, and organic waste by-products from industry, domesticated animals, and human activities. The chemical energy contained in the biomass is derived from solar energy using the process of photosynthesis. This is the process by which plants take in carbon dioxide and water, using energy from sunlight, convert them into sugars, starches,

Pyrolysis of biomass is a promising method for simultaneous production of activated carbon, bio-oil and gaseous fuels and other valuable chemicals, while the almost simultaneous pyrolysis and gasification of the fuel result in formation of solid product with high surface area and well-developed porous structure (Nickolov & Mehandjiev, 1995; Mehandjiev et al., 1997). Pyrolysis is the thermal destruction of organic macromolecules in the absence of oxygen in small molecules. The destructed portion comprises a high energy

**1. Introduction** 

increasing populations and economic development.

economic and environmental implications.

cellulose, lignin etc., and finally oxygen is produced and released.

**Obtained During the Preparation** 

**of Bio-Oil and Activated Carbon** 

Rosa Miranda, César Sosa, Diana Bustos, Eileen Carrillo and María Rodríguez-Cantú

*Universidad Autónoma de Nuevo León* 
