Binding of aqueous cadmium by the lyophilized biomass of Chlamydomonas reinhardtii

Biosorption of aqueous Cd by Chlamydomonas reinhardtii was examined. Cd uptake increased from pH 2 to 10, and was measured at different initial Cd concentrations (0.09–8.75 mM). Proton affinity models of potentiometric titration data indicated the presence of two major functional group clusters on the cell walls, corresponding to ionic strength dependent pKa values in the ranges 3.8–4.7 and 8.3–9.6, with an average functional group acidity of approximately 2 mmol of protonable charge per g of lyophilized cells. Cd-binding was not significantly affected by the presence of equimolar (and greater) concentrations of aqueous macro-ions Ca2+ and K+. FTIR spectra indicated that Cd-binding was dominated by complexation to carboxylic functional groups, and Cd sorption could be modeled with a single-site Gaussian distribution model. This study shows the potential for the use of C. reinhardtii for cadmium recovery in various water and wastewater treatment applications.