Effect of metal interference, pH and temperature on Cu and Ni biosorption by Chlorella vulgaris and Chlorella miniata

Chlorella vulgaris, an unicellular green alga which had extensively been used for wastewater nutrient removal studies, and a locally isolated Chlorella miniata were assessed for their Cu and Ni biosorption from single and mixed metal solutions. The locally isolated C. miniata had a higher maximal binding (q(max)) of 23.26 mg Cu g^-1 d.w. and 20.37 mg Ni g^-1 d.w. than the 18.72 Cu g^-1 d.w. and 12.06 mg Ni g^-1 d.w. of C. vulgaris when unit biomass was concerned. However, when normalized to surface area of the cells, C miniata showed a higher Ni but lower Cu biosorption than C vulgaris. Both Chlorella species had a preferential Cu to Ni biosorption from mixed metal solutions. The Cu biosorption by both algal biomass was not significantly affected in the presence of 30 mg l^-1 Ni. When Ni increased to 300 mg l^-1, the q(max) of Cu was reduced by 13% in C. vulgaris and 7.7% in C. miniata. On the contrary, presence of 30 mg l^-1 Cu already lowered the q(max) of Ni by 12% and 17% in C. vulgaris and C. miniata, respectively. And virtually, no Ni biosorption was observed in presence of 300 mg l^-1 Cu. Optimal Cu and Ni biosorption was found at pH 6. Although temperature had a significant effect on the biosorption process, its impact was much less than that of pH and the interference effect of Cu in the case of Ni biosorption.