Photocatalytic Reduction Mechanism of U(VI) from Uranium Mining Wastewater by Cyano-Functionalized C3N4/ZnIn2S4 Heterojunction Materials
Uranium is a key resource for nuclear energy, but its mining and processing generate large amounts of uranium-containing wastewater, posing persistent threats to the environment and human health. In this study, a cyano-functionalized C3N4/ZnIn2S4 (CCN/ZIS) heterojunction system was constructed for efficient removal of U(VI) from uranium mining wastewater. The introduction of cyano groups significantly enhanced the adsorption capacity of CCN/ZIS, reaching a maximum of 123.65 mg·g−1. Characterization techniques (UV-vis DRS, EIS, i-t, PL, TRPL) confirmed that cyano groups effectively suppress charge carrier recombination, improving photogenerated carrier separation. Under visible light, the modified material achieved over 95% removal of U(VI) within 10 minutes, demonstrating a 20-fold efficiency increase compared to pristine materials. Even in simulated uranium mining wastewater containing high concentrations of CO3^2− and F−, CCN/ZIS maintained excellent performance, overcoming the technical challenge of U(VI) removal efficiency being constrained by water quality conditions. Quenching experiments identified e− and ·O2− as the primary reactive species responsible for U(VI) reduction. This study reveals the synergistic mechanism of selective U(VI) enrichment and photoreduction, providing theoretical innovation and technological breakthroughs for uranium pollution control.