Sorption of Heavy Metals by Prepared Bacterial Cell Surfaces

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Abstract
Prepared biomass from two Gram-negative and one Gram-positive bacterial strains was examined for single, binary, and quaternary mixtures of polyvalent metal cation binding to cell surfaces. The biosorption of 24 Cr 3+ , 27 Co 2+ , 28 Ni 2+ , and 29 Cu 2+ for each bacterial cell type was evaluated using a batch equilibrium method. The binding of each metal by all three bacterial cells could be described by the Freundlich sorption model. The isotherm binding constants suggest that E. coli cells are the most efficient at binding copper, chromium, and nickel; and M. luteus adsorbs cobalt most efficiently. The K -values for copper bound to P. aeruginosa and E. coli are >2-fold and >8-fold greater, respectively, than previously reported for intact cells. The general metal-affinity series observed was Cr 3+ > Cu 2+ > Ni 2+ > Co 2+ . There was a marked lower affinity of all biosorbents for Co 2+ and Ni 2+ . M. luteus and E. coli had a strong preference for Co 2+ over Ni 2+ . Metal-binding enhancement could be ascribed to increased cell barrier surface porosity to metal-bearing solutions.