Removal and Recovery of Uranium from Groundwater Using Direct Electrochemical Reduction Method: Performance and Implications

Removal of uranium from groundwater is of great significance as compared to in situ bioimmobilization technology. In this study, a novel direct electro-reductive method has been developed to efficiently remove and recover uranium from carbonate-containing groundwater, where U(VI)O-2(CO3)(3)(4-) and Ca2U(VI)O-2(CO3)(3) are the dominant U species. The transferred electron calculations and XPS, XRD analyses confirmed that U(VI) was reduced to U(IV)O2 and accumulated on the surface of the Ti electrode (defined as Ti@U(IV)O-2 electrode) with high current efficiencies (over 90.0%). Moreover, over 98.0% of the accumulated U(IV)O-2 could be recovered by soaking the Ti@U(IV)O-2 electrode in the dilute nitric acid. Results demonstrated that the accumulated U(IV)O-2 on the surface of the Ti electrode played a key role in the removal of U(VI), which can promote the electro-reduction of U(VI). Therefore, the electrode could be used repeatedly and has a high removal capacity of U(VI) due to the continuous accumulation of active U(IV)O-2 on the surface of the electrode. Significantly, the uranium in both real and high salinity groundwater can be efficiently removed. This study implies that the proposed direct electro-reductive method has great potential for the removal and recovery of uranium from groundwater and uranium-containing wastewater.