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 (∼ 1 h) to achieve a high U(VI) extraction efficiency of > 90%. Herein, we successfully constructed WS 2 nanosheets and created in-situ oxidized domains on the surfaces (O-WS 2 ) to promote the uranium extraction and the corresponding removal kinetics. In this system, the O 7.7 -WS 2 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 7.7 -WS 2 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, 1 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.