Reduction Behavior of U(Ⅵ) by Bacillus sp.dwc-2 in Simulated Groundwater under Anaerobic Condition

The reduction behavior and the effect of various experimental conditions on U(Ⅵ) reduction by Bacillus sp.dwc-2 were investigated under anaerobic conditions at c_NaHCO3=5 mmol/L, T=303 K and pH=7.0 in simulated groundwater. TEM, EDS, SAED and XPS were carried out for sample characterization. The results show that the reduction rate increases with the contact time. The maximum U(Ⅵ) reduction rate at 24 h is 12.2%, and the reduction rates of 14.2% and 16.2% are achieved in the presence of HA and FA. The reduction rate of U(Ⅵ) increases with HA and FA concentration from 0 mg/L to 25 mg/L, then decreases due to the formation of humic coatings on the surfaces of complexes of HA and FA with U(Ⅵ) at the relatively high humic concentrations. In addition, HCO₃^- also inhibits the reduction of U(Ⅵ). Analysis of TEM-SAED and XPS confirms the existence of U(Ⅳ) during the reduction process. The above results provide basic data and reference for the reduction of U(Ⅵ) under real environment.