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, C hlorella vulgaris (a commercial species from Carolina Biological Supplies C ompany) and WW1 (an indigenous species isolated from a local sewage treatme nt works, tentatively identified as Chlorella miniata) in removing Ni2+ fro m nickel solutions with concentration ranges similar to that in electroplat ing effluents. The Ni2+ removal efficiency of C. vulgaris (around 33-41%) w as 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), respe ctively. According to Langmuir adsorption isotherms the nickel adsorption c apacity of WW1 (2985.07 mu g g(-1)) was two times greater than that of C. v ulgaris (1282.05 mu g g(-1)). These results demonstrated that WW1 was a mor e 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 concentratio ns 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.