Ni~(2+) Removal and Recovery from Electroplating Effluent by Pseudomonas putida 5-x Cell Biomass

摘要

Ni~(2+) and Cu~(2+) are the major heavy metal ions in electroplating wastewater of Hong Kong. In the present study, Pseudomonas putida 5-x cell biomass was used to remove Ni~(2+) from electroplating effluent. Ni~(2+) adsorption capacity of P. putida 5-x cell biomass cultured in sulphate-limiting medium was found to be minimum in early logarithmic growth phase, and maximum of 28.1 mg g~(-1) in late stationary growth phase. Pretreated cells by 0.1 mol L~(-1) HCl could greatly enhance the Ni~(2+) adsorption capacity of cell biomass from 28.1 to 36.7 mg g~(-1) and had no significant effect on biomass loss. The adsorption process of P. putida 5-x fresh cells and pretreated cell all could be expressed with Freundlich isotherm. TEM analyses indicated that acidic pretreatment degraded the superficial layer-capsule outside of the fresh cell to improve the adsorption capacity of cell to Ni~(2+). The Ni~(2+) bound by P. putida 5-x cell biomass could be efficiently recovered using 0.1 mol L~(-1) HCl, and the cell biomass could be reused at least five cycles for Ni~(2+) removal and recovery with 93% above removal efficiency and 98% above recovery rate. Owing to the Cu~(2+) presented in electroplating wastewater inhibiting Ni~(2+) adsorption process by P. putida 5-x cell biomass, two-stage biosorption processes should be designed to remove and recover Cu~(2+) and Ni~(2+) sequentially from electroplating effluent.