Uptake of lead, cadmium and zinc by a novel bacterial exopolysaccharide

The biosorption of the three metallic ions, lead, cadmium and zinc, in single component and bi-component mixtures in aqueous solutions by an exopolysaccharide (EPS) is reported. The isotherms are plotted to obtain the maximum of uptake capacities and apparent dissociation constants. A comparison is made between the one metal sorption system and the influence of a second metal on the uptake of the primary one. The competitive effect on the uptake of various heavy metals on the Alteromonas macleodii subsp fijiensis has been studied using the Langmuir model for bisolute systems; The isotherms indicate a competition for the same binding site with zinc and cadmium. Lead is preferentially complexed by EPS in the bi-component solutions. The hydrothermal bacterial exopolysaccharide is shown to possess an affinity for the tested metal ions which makes its use as a biosorbent a possible alternative to the other common methods. (C) 1997 Elsevier Science Ltd.