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.