Efficient photoreduction removal of uranium(VI) by O, K co-doped g-C3N4 under air atmosphere without sacrificial agents

Photocatalytic reduction of soluble hexavalent uranium to insoluble tetravalent uranium is a promising strategy for uranium-containing wastewater treatment, while this method generally requires anaerobic conditions and/or the addition of sacrificial agents. Obviously, providing anaerobic environment and sacrificial agent will not only increase the cost but also causes secondary pollution. Thus, efficient removal of U(VI) by photocatalytic techniques under air atmosphere without sacrificial agents is an urgent task and great challenge. In this work, a novel O, K co-doped g-C3N4 (OKDCN) photocatalyst was synthesized by a simple thermal reaction for the photoreduction removal of U(VI) under air atmosphere without sacrificial agents. Batch experiments show that the OKDCN-2 can nearly completely remove U(VI) in the solution within 120 min at pH 5.0. In addition, the OKDCN showed excellent reusability and selectivity in the process of photocatalytic reduction of U(VI). Further mechanism studies show the doping of O and K can improve the photogenerated carrier transfer and separation efficiency of OKDCN, and then improve the performance of photocatalytic reduction of uranium. These results provide a reference for breaking through some bottleneck issues in the research field of photocatalytic removal of U(VI).