SORPTION OF HEAVY-METALS BY PREPARED BACTERIAL-CELL SURFACES

Prepared biomass from two Gram-negative and one Gram-positive bacteria l strains was examined for single, binary, and quaternary mixtures of polyvalent metal cation binding to cell surfaces. The biosorption of C r-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 ea ch metal by all three bacterial cells could be described by the Freund lich sorption model. The isotherm binding constants suggest that E. co li cells are the most efficient at binding copper, chromium, and nicke l; and M. luteus adsorbs cobalt most efficiently. The K-values for cop per 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 w as a marked lower affinity of all biosorbents for Co2+ and Ni2+. M. lu teus and E. coli had a strong preference for Co2+ over Ni2+. Metal-bin ding enhancement could be ascribed to increased cell barrier surface p orosity to metal-bearing solutions.