Abstract
The adsorption of some heavy metals onto the walls of harvested, washed, and dried non-living biomass cells of different Pseudomonas strains was studied at optimum experimental conditions using a simplified single component system. The Langmuir adsorption model was found to be a suitable approach to describe the system via multi-step processes. Isotherms measured at 30.0°C and pH 5.5 with [M]
total
= 10-100 mM for tight, reversible Cr
6+
(aq), Ni
2+
(aq), Cu
2+
(aq) and Cd
2+
(aq) binding by the cell walls of the investigated biomass fit the Langmuir model and give the pH-independent stoichiometric site capacities ν
i
and equilibrium constants K
i
for metal binding at specific biomass sites i = A, B, C, and D. Tight binding sites A, B, and D of the non-living biomass are occupied by Cr
VI
, sites A and C by Ni
II
, sites A and D by Cd
II
, and only site B by Cu
II
. It is concluded that ν
i
is a stoichiometric parameter that is independent of the magnitude of K
i
for binding site i and that the studied heavy metals selectively and tightly bind at different biomass sites.