115
from agricultural materials and further modified to enhance the adsorption capacity
(Kyzas and Kostoglou 2014). Several researchers (Hokkanen et al. 2016; O’Connell
et al. 2008) reviewed the modification methods of the cellulose-based materials to
increase its adsorption capacity. In the past years, people have tried to use various
cellulosic agricultural waste materials, such as sugarcane bagasse (Gupta and Ali
2004; Mohan and Singh 2002), rice husk (Ajmal et al. 2003; Srinivasan 1998), sawdust (Kadirvelu et al. 2003; Selvi et al. 2001), coconut husk (Tan et al. 1993), rice
mill wastes, neem leaves, coconut shell, hyacinth roots (Singha and Das 2012), rubber leaf (Nag et al. 2015), etc., for heavy metal removal and noted their adsorptive
potential.
The above observations suggest cellulosic materials can be used for metal
removal processes in raw form without any surface modifications. However, acid or
alkali treatment and some more specific treatments enhance their adsorption potential, and the modified cellulose is formed. Some examples of modified cellulose are
cellulose gels, beads, derivatives, composites, holocellulose, and so on. They are
biodegradable and non-toxic and have huge adsorption capacity. A critical review
was conducted to assess the potential of cellulosic materials in wastewater treatment.
5.2 Availability, Uses, Types, and Properties
of Cellulosic Materials
Cellulose is widely available in nature. Plants are grown throughout the world and
cellulose is present in the cell wall in high amount. The major sources are fibers of
various plants, like cotton, jute, hemp, flax, and many more. The plant wood consists of 45–50% of cellulose (Holtzapple 2003) and is an important source of our
dietary fiber. It has many other uses, like manufacturing of paper, plastic, film, some
kinds of clothes, alternative source of energy, different chemicals, etc. The cellulose
content of various plant sources is presented in Table 5.1.
The simplest form of sugar is known as glucose which is produced by plants
through the process of photosynthesis and stored as long-chained polymeric form
known as cellulose. It is a complex carbohydrate with carbon, oxygen, and hydrogen
having common structure [C m (H 2 O) n ] and is made up of a number of D-anhydroglucose
pyranose or simply glucose units. These glucose units jointly form a fundamental
cellulose unit, known as β-(1–4)-glycosidic bonds (Gupta et al. 2016). Figure 5.1(a
and b) depicts the common structure of glucose and cellulose, while Fig. 5.2 demonstrates the scanning electron microscopic image of rubber leaf, a common cellulosic material at a magnification of 15,000X. Natural sources of cellulosic materials
and preparation of useful adsorbents from them are presented in Fig. 5.3.
Cellulose is hydrophilic and non-toxic and has good mechanical strength and
returns to the carbon cycle by natural decay. Methyl and hydroxyl functional group
is present in one repeating molecule of cellulose, and the functional groups contribute in metal binding. It is a semi-crystalline linear polymer and has both crystalline
5 Cellulose-Based Adsorbents for Heavy Metal Removal
from agricultural materials and further modified to enhance the adsorption capacity
(Kyzas and Kostoglou 2014). Several researchers (Hokkanen et al. 2016; O’Connell
et al. 2008) reviewed the modification methods of the cellulose-based materials to
increase its adsorption capacity. In the past years, people have tried to use various
cellulosic agricultural waste materials, such as sugarcane bagasse (Gupta and Ali
2004; Mohan and Singh 2002), rice husk (Ajmal et al. 2003; Srinivasan 1998), sawdust (Kadirvelu et al. 2003; Selvi et al. 2001), coconut husk (Tan et al. 1993), rice
mill wastes, neem leaves, coconut shell, hyacinth roots (Singha and Das 2012), rubber leaf (Nag et al. 2015), etc., for heavy metal removal and noted their adsorptive
potential.
The above observations suggest cellulosic materials can be used for metal
removal processes in raw form without any surface modifications. However, acid or
alkali treatment and some more specific treatments enhance their adsorption potential, and the modified cellulose is formed. Some examples of modified cellulose are
cellulose gels, beads, derivatives, composites, holocellulose, and so on. They are
biodegradable and non-toxic and have huge adsorption capacity. A critical review
was conducted to assess the potential of cellulosic materials in wastewater treatment.
5.2 Availability, Uses, Types, and Properties
of Cellulosic Materials
Cellulose is widely available in nature. Plants are grown throughout the world and
cellulose is present in the cell wall in high amount. The major sources are fibers of
various plants, like cotton, jute, hemp, flax, and many more. The plant wood consists of 45–50% of cellulose (Holtzapple 2003) and is an important source of our
dietary fiber. It has many other uses, like manufacturing of paper, plastic, film, some
kinds of clothes, alternative source of energy, different chemicals, etc. The cellulose
content of various plant sources is presented in Table 5.1.
The simplest form of sugar is known as glucose which is produced by plants
through the process of photosynthesis and stored as long-chained polymeric form
known as cellulose. It is a complex carbohydrate with carbon, oxygen, and hydrogen
having common structure [C m (H 2 O) n ] and is made up of a number of D-anhydroglucose
pyranose or simply glucose units. These glucose units jointly form a fundamental
cellulose unit, known as β-(1–4)-glycosidic bonds (Gupta et al. 2016). Figure 5.1(a
and b) depicts the common structure of glucose and cellulose, while Fig. 5.2 demonstrates the scanning electron microscopic image of rubber leaf, a common cellulosic material at a magnification of 15,000X. Natural sources of cellulosic materials
and preparation of useful adsorbents from them are presented in Fig. 5.3.
Cellulose is hydrophilic and non-toxic and has good mechanical strength and
returns to the carbon cycle by natural decay. Methyl and hydroxyl functional group
is present in one repeating molecule of cellulose, and the functional groups contribute in metal binding. It is a semi-crystalline linear polymer and has both crystalline
5 Cellulose-Based Adsorbents for Heavy Metal Removal