SORPTION OF HEAVY-METALS BY PREPARED BACTERIAL-CELL SURFACES

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 Cr-24(3+), Co-27(2+), Ni-28(2+), and Cu-29(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 Cr3+ > Cu2+ > Ni2+ > Co2+. There was a marked lower affinity of all biosorbents for Co2+ and Ni2+. M. luteus and E. coli had a strong preference for Co2+ over Ni2+. Metal-binding enhancement could be ascribed to increased cell barrier surface porosity to metal-bearing solutions.