Nickel biosorption by two chlorella species, C-Vulgaris (a commercial species) and C-Miniata (a local isolate)

The present study compared the efficiency of two unicellular green algae, Chlorella vulgaris (a commercial species from Carolina Biological Supplies Company) and WW1 (an indigenous species isolated from a local sewage treatment works, tentatively identified as Chlorella miniata) in removing Ni2+ from nickel solutions with concentration ranges similar to that in electroplating effluents. The Ni2+ removal efficiency of C. vulgaris (around 33-41%) was significantly lower than that of WW1 (more than 99%) in nickel solutions from 10 to 40 mu g ml(-1). The maximum Ni2+ uptake by C. vulgaris and WW1 under the present batch experiment was 641.76 and 1367.62 mu g g(-1), respectively. According to Langmuir adsorption isotherms the nickel adsorption capacity of WW1 (2985.07 mu g g(-1)) was two times greater than that of C. vulgaris (1282.05 mu g g(-1)). These results demonstrated that WW1 was a more powerful Ni2+ biosorbent than C. vulgaris. In both species, most Ni2+ in solution was sequestered by the algal cells within the first few minutes of treatment. The cellular Ni2+ concentration increased with the concentrations of nickel in solution. After treating Ni-containing wastewater for 24 h, both species were still capable of cell division, but the growth rate was reduced in proportion to the concentrations of nickel in the wastewaters. (C) 2000 Elsevier Science Ltd. All rights reserved.