Bioaccumulation and biosorption of Cd2+ and Zn2+ by bacteria isolated from a zinc mine in Thailand

The three bacteria, Tsukamurella paurometabola A155, Pseudomonas aeruginosa B237, and Cupriavidus taiwanensis E324, were isolated from soils collected from a zinc mine in Tak Province, Thailand. Among these bacteria, P. aeruginosa B237 and C. taiwanensis E324 were tolerant of both cadmium and zinc, while paurometabola A155 was highly tolerant of zinc only. Bioaccumulation experiment revealed that Cd2+ and Zn2+ were mainly adsorbed on the cell walls of these bacteria rather than accumulated inside the cells. During Cd2+ and Zn2+ biosorption, P. aeruginosa B237 and T. paurometabola A155 showed the highest removal efficiencies for Cd2+ and Zn2+, respectively. The maximum biosorption capacities of P. aeruginosa B237 and T paurometabola A155 biomasses for Cd2+ and Zn2+ biosorptions were 16.89 and 16.75 mg g(-1), respectively, under optimal conditions. The experimental data of Cd2+ and Zn2+ biosorptions fitted well with Langmuir isotherm model, suggesting that Cd2+ and Zn2+ adsorptions occurred in a monolayer pattern on a homogeneous surface. Furthermore, the pseudo-second order and pseudo-first order kinetic models best described the biosorption kinetics of Cce(+) and Zn2+ adsorptions, respectively, suggesting that the Gd2+ and Zn2+ adsorptions took place mainly by chemisorption (Cd2+) and physisorption (Zn2+). (C) 2015 Elsevier Inc. All rights reserved.