Constructing Stable Nitrogen-Rich Core–Shell CdS@MC for Photocatalytic Reduction of U(VI) in Air without Sacrificial Agent

Photocatalytic reduction of uranium from U(VI) to U(IV) has been recognized as an effective treatment method for uranium wastewater. However, most photocatalysts have to be reduced under inert gas and sacrificial agent. Here, a class of nitrogen-rich core–shell photocatalysts (CdS@MC) with high stability was successfully prepared by modifying CdS with melamine and cyanuric chloride condensation. When the initial concentration of U(VI) was 100 mg/L and the solid–liquid ratio was 0.2 g/L, the removal of U(VI) by CdS@MC without sacrificial agent under air could reached 95%. The removal rate was still above 80% after five cycles with good stability and good removal rate of U(VI) at high salt concentration. CdS@MC not only efficiently generates electrons for photocatalytic reduction of U(VI), but also generates H2O2 from O2, which then reacts with uranyl ions to produce metastudtite. This study provides a new direction for the study of efficient uranium removal photocatalysts without sacrificial agent in air environment.