Abstract
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 (qmax) 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 qmax 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 qmax 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.