Chapter 10 - Microbial biosorbents for heavy metal removal

Abstract

The continuous discharge of untreated effluents from industries associated with fertilizers, metallurgy, leather, aerospace, photography, mining, electroplating, pesticide, surface finishing, iron and steel, energy and fuel production, electrolysis, metal surface treating, electroosmosis, and appliance manufacturing has increased the global threat of heavy metal contamination in water bodies and the overall ecosystem. Toxic heavy metals such as chromium (Cr), lead (Pb), zinc (Zn), arsenic (As), copper (Cu), nickel (Ni), cobalt (Co), cadmium (Cd), and mercury (Hg) are nonbiodegradable and tend to accumulate in living organisms, leading to several diseases. Conventional methods for heavy metal removal are extremely expensive and inefficient when applied for larger volumes of water. Moreover, these methods generate huge amounts of sludge and other toxic products for which disposal is a matter of concern. As environment-friendly alternatives, microbial biosorption and bioaccumulation have emerged recently, which involve bacteria, cyanobacteria, algae, and fungi. Herein, we present an elaborate description of various mechanisms of biosorption such as complexation, chelation, coordination, ion exchange, precipitation, and reduction. Exotic nanostructures formed by biosorption are also included, indicating the significance of nanobiotechnology in heavy metal removal. Furthermore, various process parameters (such as pH, temperature, initial concentration of the metal ions, biosorbent dose, and speed of agitation) are also discussed, which highly affect the overall biosorption process. Various biomass modification strategies by physical and chemical treatment before use and economical aspects, owing to regeneration and reuse of microbial biosorbents after removing the heavy metals, are also highlighted in the chapter, along with their applications.