Removal of chromium(VI) and zinc(II) from aqueous solution using kaolin-supported bacterial biofilms of Gram-negative E. coli and Gram-positive Staphylococcus epidermidis

In this study, the capacity of Escherichia coli and Staphylococcus epidermidis biofilms supported on kaolin in the removal of Cr(VI) and Zn(II) from aqueous solution was investigated in batch assays. The effect of initial metal concentration and contact time on the removal efficiency of Cr(VI) and Zn(II) using E. coli and S. epidermidis biofilms supported on kaolin. Isotherm studies show that the Freundlich isotherm best describes the Zn(II) biosorption by E. coli and S. epidermidis biofilms and Cr(VI) biosorption onto S. epidermidis biofilm, and Langmuir isotherm for Cr(VI) biosorption by E. coli biofilm supported on kaolin. The kinetics of Cr(VI) and Zn(II) best fits the pseudo-second order kinetic model (R-2 > 0.98), which implies that chemisorption is the rate-limiting step. The adsorptive capacity of Gram-negative E. coli is higher than the Gram-positive S. epidermidis in the removal of Cr(VI) and Zn(II) from aqueous solution. (C) 2018 Chinese Institute of Environmental Engineering, Taiwan. Production and hosting by Elsevier B.V.