Adsorption equilibria of cadmium on algal biomass

Adsorption equilibria of cadmium on the non-living algal biomass of Chlorella vulgaris were studied using batch stinted-tank methods. The adsorption process was rapid, achieving equilibrium in a few minutes. Environmental factors such as pH, biomass dosage and buffer concentration had a considerable influence on the equilibrium isotherms. The adsorption capacity of the biomass increased with increasing pH. This behaviour was attributed to decreased protonation of the binding sites and decreased competition for binding between the cadmium ions and protons with increasing pH. The equilibrium data measured at different pH values were consistent with the influence of pH on the zeta potentials of the biomass, indicating that the dominant binding mechanism is likely to involve electrical attractions.