An overview and recent progress in the heterogeneous photocatalytic reduction of U(VI)

The utilization of light-driven heterogeneous photocatalytic technology is extremely appealing for the uranium(VI) reduction since it is promising in seawater uranium extraction and uranium wastes treatment. U(VI) recovery through heterogeneous photocatalysis is more efficient, economic, non-pollutant, and of high selectivity compared to other methods. However, the systematic summarization on U(VI) photocatalytic reduction from water system is indeed scarce, especially, there are several discrepant hypotheses on the photocatalytic process and mechanisms of the reduction of U(VI). Therefore, this review would provide an overview and recent progress in the photocatalytic U(VI) reduction for the first time. The background of the photocatalytic U(VI) reduction is firstly introduced, followed by the discussion of the photocatalytic reduction mechanisms of U(VI). Thereafter, the photocatalysts widely used in the photocatalytic reduction of U(VI) are summarized. Subsequently, the influence of environmental factors such as organic matters, pH, coexisting ions, and dissolved oxygen on the photocatalytic U(VI) reduction is described. Finally, the challenges and the future perspectives of the photocatalytic reduction of U(VI) are addressed. (C) 2019 Elsevier B.V. All rights reserved.