Comparative studies on the microbial adsorption of heavy metals

A process of competitive biosorption of Cr(VI) and Fe(III) ions on Streptococcus equisimilis, Saccharomyces cerevisiae and Aspergillus niger is described and compared to single metal ion adsorption in solution. The ability of these three microorganisms to adsorb metal ions [Cr(VI) and Fe(III)], is shown as a function of metal concentration, pH, temperature, growth medium composition, culture age and contact time with the biosorbents. The effect of addition of an extra energy source in the form of glucose, fructose and sucrose in the adsorption medium is studied for the biosorption of metal ions by microorganisms. Freundlich constants are determined from the Freundlich adsorption isotherms for all the organisms. The adsorbed metals from the sorbents can be regenerated in situ with 0.1 M sodium hydroxide. (C) 2002 Elsevier Science Ltd. All rights reserved.