ABSTRACT
Heavy metals in trace quantities are important to all living organisms to regulate physiological developments (Park et al. 2006). However, metal concentrations in the environment often exceed permissible levels due to the rampant discharge of high loads of metals from vigorous urbanisation, industrialisation and anthropogenic activities. The metal-laden waste effluents come primarily from the following industries (but are not confined to them): the metallurgy industry, surface-finishing industry, energy and fuel production industry and fertilizer and pesticide industry. Effluents from each of these industries vary in the type and concentration of heavy metals discharged. Heavy metals of major concern include toxic metals (Hg, Cr, Pb, Zn, Cu, Ni, Cd, As, Co and Sn), radionuclides (U, Th, Ra and Am) and precious metals (Pd, Pt, Ag, Au and Ru) (Wang and Chen 2006). Among these metals, lead (Pb), copper (Cu), mercury (Hg), cadmium (Cd) and chromium (Cr) are key environmental pollutants (Gadd and Fomima 2011). Metal toxicity is the
CONTENTS
2.1 Introduction .................................................................................................. 31 2.2 Microbes for Heavy Metal Removal .........................................................33 2.3 Dead Microbial Cells for Metal Removal ................................................. 41 2.4 Isotherm and Kinetic Models for Biosorption Processes and
Mechanisms ..................................................................................................44 2.5 Live Microbial Cells for Metal Removal ...................................................46 2.6 Innovations of Dead and Live Microbial Cells for Metal Removal ......50 2.7 Conclusions ...................................................................................................58 2.8 Perspectives ..................................................................................................58 Acknowledgements .............................................................................................. 59 References ............................................................................................................... 59
result of frequent discharge and accumulation (and, in some cases, the biomagnification) of these metals in the environment. Their persistence in the environment is enhanced by their ability to exist as various chemical species attributed to their interaction with biotic and abiotic environmental factors. Metals exist as cations or anions, in oxidised or reduced forms or in complex or hydroxylated metal forms (Gadd 2009). These bioavailable forms cause toxicity upon uptake by living organisms (microbes, plants, animals and humans) posing serious health and environmental hazards (Manasi et al. 2014). Excessive Cu, Cd and nickel (Ni) are known to cause liver and kidney failure as well as chronic asthma (Dal Bosco et al. 2006).
