Z-Scheme heterojunction Cu2(OH)3F/Bi2WO6 with improved photocatalytic activity for uranium removal from wastewater under air atmosphere

Abstract

The proper treatment of uranium-contaminated nuclear wastewater is important for uranium resource recovery and environmental protection. Photocatalytic strategies have emerged as promising approaches for improving uranium removal efficiency. In this study, a Z-scheme heterojunction Cu2(OH)3F/Bi2WO6 (CFO/BWO) was synthesized by directly depositing CFO onto a BWO semiconductor for highly efficient photocatalytic removal of uranium from wastewater. The CFO semiconductor contains abundant O–H bonds and a high conduction band position, which can couple with BWO to form a heterojunction via interactions between the O and W atoms. Owing to the high electronegativity of CFO, electrons easily transfer from BWO to CFO, resulting in enhanced electron-hole separation and promoted electron transmission. Importantly, introducing CFO narrowed the bandgap of CFO/BWO compared to that of BWO, providing an appropriate band position, which is more conducive to the photocatalytic immobilization of uranium. Moreover, the mechanism of CFO/BWO heterojunction for photocatalytic immobilization of uranium revealed the formation of a stable crystalline phase of (UO2)O2·2H2O during the photocatalytic process. As a result, CFO/BWO could remove 91 % of uranium from simulated wastewater under an air atmosphere. The findings of this study provide a promising strategy by regulating the band position of heterojunctions for photocatalytic immobilization of uranium.