Preparation of ZnS/CdS heterostructure for the photocatalytic reduction of uranium under the natural light

This work successfully synthesized a series of ZnS/CdS photocatalysts (ZC) via one-step hydrothermal method, in which ZC-1 (Zn/Cd = 2:1) exhibited optimal photoreduction performances of hexavalent uranium (U(VI)). The experiments results demonstrated that the reaction rate constant of ZC-1 (k = 0.0174 min −1 ) was 4.49 and 23.51 times higher than those of pristine ZnS and CdS, respectively, confirming that the combination of ZnS and CdS was a feasible strategy for remarkably strengthening the activity of U(VI) photocatalytic reduction. Meanwhile, ZC-1 reached high removal efficiency of 80.18% with an initial U(VI) concentration as high as 180 mg/L, posing a considerable U(VI) extraction capacity of 1443.26 mg/g, which was larger than numerous photocatalysts. The wonderful performances of ZC-1 might be due to its well-dispersed morphology and optimized band structure, which not only provided rich active sites, but also endowed ZC-1 with enhanced capacity of visible light harvesting and photogenerated electron-hole separation. In addition, ZC-1 demonstrated exceptional anti-interference ability and outstanding photocatalytic stability, maintaining a high U(VI) photoreduction rate of over 88% after 5 cycles. The mechanistic study showed that the effective extraction efficiency of U(VI) for ZC-1 was ascribed to the “cooperative capture and directional reduction” mechanism: The built-in electric field concentrated reductive electrons at catalytic active sites to facilitate the U(VI) reduction process, while the well-dispersed of ZC-1 synergistically enhanced UO 2 2+ capture. This study established a novel design strategy and fundamental theoretical framework for developing efficient and stable photocatalytic materials to deal with U(VI) pollution.