Chitosan-based Materials in Waste Water Treatment––Recent Developments - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 23

activated Carbon as an adsorbent
The first introduction for heavy metals removal, activated carbon has undoubtedly
been the most popular and widely used adsorbent in wastewater treatment applications
throughout the world (Babel and Kurniawan, 2003). This capacity is mainly due to its
structural characteristics and porous texture, which gives it a large surface area and its
chemical nature, which can be easily modified by chemical treatment in order to in-
crease the properties. However, activated carbon, presents several disadvantages. It is
non-selective, quite expensive, and higher the quality, greater the cost. The regenera-
tion of saturated carbon by thermal and chemical procedure is also expensive, and re-
sults in loss of the adsorbent. This had led many workers to search for more economic
and efficient adsorbents. Due to the problems mentioned above, research interest in
to the production of alternative sorbents to replace the costly activated carbon has
intensified in recent years. Attention has focused on various adsorbents, in particular
natural solid supports, which are able to remove pollutants from contaminated water
at low cost (Crini, 2005).
Natural-polymers as adsorbents
Recently numerous approaches have been studied for the development of cheaper and
more effective adsorbents containing natural polymers. The removal of metals, com-
pounds and particulates from solution by biological material is recognized as an exten-
sion to adsorption and is named as biosorption (Boddu et al., 2003). Many biosorptive
agents such as fungi (Acosta et al., 2004), algae (Gupta et al., 2001), seaweeds (Elangovan
et al., 2008; Kratochvil et al., 1998), microorganisms (Fan et al., 2008; Sahin and
Ozturk, 2005), and several biopolymers (Bailey et al., 1999; Wu et al., 2008) have
been utilized in the removal of heavy metals from wastewater. The polysaccharides
are renewable resources which are currently being explored intensively for their appli-
cations in water treatment (Gupta and Ravikumar, 2000). Among the polysaccharide
compounds such as chitin (Ravikumar, 2000), starch (WurzburgIn, 1986) and their
derivatives, chitosan (Varma et al., 2004), deserve particular attention. These polysac-
charides are abundant, renewable, and biodegradable, low-cost and are the best choice
in water treatment and useful tool for protecting the environment (Bolto, 1995).
advantages of using Natural materials for adsorption
Generally, a suitable adsorbent for adsorption process of pollutants should meet sev-
eral requirements such as
(a) Efficient for removal of a wide variety of target pollutants,
(b) High capacity and rate of adsorption,
(c) Important selectivity for different concentrations,
(d) Granular type with good surface area,
(e) High physical strength,
(f) Able to be regenerated if required,
(g) Tolerant for a wide range of wastewater parameters, and
(h) Low cost.