12. Bacterial Biosorption: A Technique for Remediation of Heavy Metals

Bacterial biosorption can be used for the removal of pollutants from waters contaminated with pollutants that are not easily biodegradable, such as metals and dyes. A variety of biomaterials are known to bind these pollutants including bacteria, fungi, algae, and certain industrial and agricultural wastes. Biosorbents are less costly and more effective alternatives for the removal of metallic elements, especially heavy metals, from aqueous solution. In this chapter, the sorption abilities of bacterial biomass toward metal ions are emphasized. The appropriate conditions for immobilizing bacteria for maximum biosorption and the mechanism(s) involved are highlighted. The properties of cell wall constituents, such as peptidoglycan, and the role of functional groups, such as carboxyl, amine, and phosphonate, are discussed on the basis of their biosorption potentials. Binding mechanisms as well as the parameters influencing passive uptake of pollutants are analyzed. A detailed description of isotherm and kinetic models and the importance of mechanistic modeling are presented. To enhance biosorption capacity, biomass modifications through chemical methods and genetic engineering are needed for the effective removal of metal. For continuous treatment of effluents, a packed column configuration is suggested and the factors influencing its performance are discussed. The chapter also highlights the necessity for examination of biosorbents within real-world situations, as competition between solutes and water quality may affect biosorption performance. Thus, this chapter reviews the achievements and current status of biosorption technology and provides insights into this research frontier.