Enhanced photoreduction of U(VI) on WO3 nanosheets by oxygen defect engineering

The efficient, safe, and low-cost treatment of uranium-containing wastewater is still an urgent and meaningful problem. The uranium-containing wastewater system commonly contains a variety of soluble organics, which complex with hexavalent uranium (U(VI)) and thus increase the difficulty for U(VI) treatment. Herein, we introduced oxygen vacancy into WO3 nanosheets to achieve highly efficient photocatalytic reduction of U(VI) and photo-degradation of organics. The WO2.78 nanosheets showed U(VI) removal ratio of 95.6% with the reduction ratio of 84.5% in 8 mg/L of U(VI). Additionally, the maximum extraction capacity of U(VI) on WO2.78 nanosheets reached 507.2 mg/g at 200 mg/L of U(VI). Meanwhile, the presence of excessive interfering ions and the cycle use of the WO2.78 nanosheets hardly decreased the removal ratio of U(VI). The mechanistic study demonstrated that the introduction of oxygen vacancies not only broadened the response range of visible light, but also increased the adsorption of U(VI) over WO3 nanosheets. Moreover, the decreased reduction potential of WO2.78 nanosheets to U(VI) verified the enhanced photocatalytic activity of WO2.78 nanosheets. Our work provided a successful example for the promotion of reduction efficiency toward U(VI) pollutants by the vacancy engineering in metal oxides.