In-situ oxidized tungsten disulfide nanosheets achieve ultrafast photocatalytic extraction of uranium through hydroxyl-mediated binding and reduction

Photoreduction of hexavalent uranium (U(VI)) by semiconductor provides a novel and effective avenue for uranium extraction. Unfortunately, the traditional metal oxide and sulfide semiconductors suffer from the lack of confinement sites to U(VI), which resulted in the long period (similar to 1 h) to achieve a high U(VI) extraction efficiency of > 90%. Herein, we successfully constructed WS2 nanosheets and created in-situ oxidized domains on the surfaces (O-WS2) to promote the uranium extraction and the corresponding removal kinetics. In this system, the O-77-WS2 nanosheets exhibited a considerable U(VI) extraction efficiency of > 90% within 20 min in 8 mg.L-1 U(VI)-containing solution, which represented the highly efficient U(VI) removal performance. In 200 mg.L-1 U(VI)-containing solution, the O-77-WS2 nanosheets exhibited an extraction capacity of 652.4 mg g(-1). The mechanism study revealed that the oxidized surface tended to trap hydrogen atom and in-situ form hydroxyl groups in defect sites. Evidenced by a series of experiment, such as kinetic isotope effect, 'H nuclear magnetic resonance (NMR) spectra, and X-ray absorption near-edge structure (XANES) spectra, the in-situ formed hydroxyl groups participated in the uranium reduction, which dramatically enhanced uranium extraction kinetics and efficiency.

Automated summary

The construction of WS2 nanosheets with an oxidized surface showed highly efficient uranium extraction and removal. The O-77-WS2 nanosheets exhibited a high extraction efficiency and capacity for U(VI), possibly due to the involvement of in-situ formed hydroxyl groups in the reduction process.