Bioremoval of Cu2+ from CMP wastewater by a novel copper-resistant bacterium Cupriavidus gilardii CR3: characteristics and mechanisms

Bacteria of the genus Cupriavidus are known for the ability of resistance to various heavy metals and metal-binding capability. Herein, we investigated the bioremoval of Cu2+ from synthesized chemical-mechanical polishing (CMP) wastewater by living cells of Cupriavidus gilardii CR3, a novel copper-resistant bacterium isolated in our previous study. The surface topography changes of strain CR3 were observed by SEMEDX, where images showed that binding took place on the bacterial cell surface. FTIR spectra provided evidence that carboxyl, hydroxyl, amino, and phosphate groups on the surface of strain CR3 could be available for characteristic coordination bonding with Cu2+. Zeta potential confirmed that electrostatic interaction was involved in Cu2+ binding. The biosorption and bioaccumulation of Cu2+ by strain CR3 was highly pH-dependent, and the optimum pH value was 5.0. The maximum binding capacity for Cu2+ was 18.33 mg g(-1) and the bioremoval efficiency was 27% under optimal conditions. The Cu2+ binding process obeyed the Langmuir isotherm (R-2 - 0.99). Kinetic data were properly fitted with both pseudo-second order kinetic model (R-2 - 0.99) and an intraparticle diffusion model (R-2 - 0.98). It can be concluded that living cells of C. gilardii CR3 have the potential to be utilized for the removal of Cu2+ from CMP wastewater.