MnOx-decorated oxygen-doped g-C3N4 with enhanced photocatalytic activity for efficient removal of uranium(VI)

Photocatalysis can convert soluble hexavalent uranium (U(VI)) to insoluble tetravalent uranium (U(IV)), which can then be removed and recovered from water, making it a promising method for treating uranium-containing wastewater. In this study, we developed a novel MnOx-decorated oxygen-doped g-C3N4 (OCNM) photocatalyst for efficient photocatalytic extraction of uranium from uranium-containing wastewater. The oxygen doping and surface-decorated MnOx can synergistic promote the response of visible light and separation and transfer efficiency of photogenerated carriers, resulting in excellent performance of OCNM for photocatalytic extraction of uranium. Under aerobic and visible LED light irradiation, the as-synthesized OCNM can almost completely remove U(VI) in uranium solution with a concentration range of 1–100 mg/L at pH 5.0. The removal rate of U(VI) by OCNM remained (91.8%) after 5 consecutive adsorption–desorption cycles tests, indicating that this material is highly recyclable. Furthermore, the OCNM exhibits high selectivity for U(VI) in coexisting metal ion solutions. Further mechanism study revealed that the photogenerated e- and ·O2– play an important role in U(VI) removal, with the U(VI) being immobilized as schoepite ((UO2)8O2(OH)12·12H2O) by OCNM during the photocatalytic reaction. This study presents a promising material and approach for the effective treatment of uranium wastewater using photocatalytic technology.