Enhanced removal of aqueous uranium: Photocatalytic U(VI) reduction over bismuth vanadate/hydrothermal carbon nitride under visible light

Photocatalytic removal of hexavalent uranium is an effective method for reducing radioactive uranium contamination in water. Herein, novel heterojunction catalysts, bismuth vanadate/hydrothermal carbon nitride (BiVO4/HCN), were synthesized and firstly successfully implemented for uranium removal. For example, the removal rate of U(VI) over 0.10BiVO4/HCN reached 98.5 % for the first time and more than 95.9 % for five consecutive cycles. Subsequent characterization analyzes confirmed that increased specific surface area, redshift of the absorption band, and efficient charge separation of the photogenerated electron-hole pairs collectively contributed to the improved photocatalytic performance. Noteworthily, free radical quenching and electron spin resonance spectroscopy results indicate that holes, photogenerated electrons, and superoxide radicals are the major active species for the photoreduction of U(VI). Finally, a possible photocatalytic mechanism of U(VI) removal was proposed.