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Interactions of Chitosan with Metals for Water Purification

Increased environmental concerns have made the control and treatment of liquid effluents, mainly wastewaters, discharged by various industries such as mining, food processing, petrochemicals, and so on, an integral part of operational systems. These wastewaters may contain organic and inorganic contaminants such as suspended solid particles, dyes, pesticides, and heavy metals. The potential of these contaminants to negatively impact aquatic ecosystems and drinking water resources necessitates that wastewaters either be recycled back to processing circuits for reuse or treated prior to disposal or release to the environment. Thus, the contaminants must be effectively removed to meet increasingly stringent environmental quality standards. Some natural biopolymers such as chitosan are being recognized as efficient materials used for wastewater treatment. Chitin is the secondmost widely produced polymer in the biosphere after cellulose and is composed of N-acetylglucosamine monomer units linked by a b (1! 4) glycosidic bond. It is commonly found in the exoskeletons or cuticles of many invertebrates and in the cell walls of most fungi and some algae (Ruiz-Herrera, 1978; Jeuniaux, 1982). Chitosan is a deacetylated derivative of chitin (Muzzarelli, 1977; Roberts, 1992; Rinaudo, 2006). However, in almost all cases, monomers of chitin are not actually all acetylated, and likewise for the chitosan, the monomers are not all deacetylated. In fact, chitin and chitosan correspond to copolymers consisting of a sequence of N-acetyl-D-glucosamine and D-glucosamine units (Figure 4.1).