ZIF-67/Ag₃VO₄ based S-scheme heterojunction for visible light driven rapid photocatalytic removal of venlafaxine

A binary S-scheme heterojunction photocatalyst, ZIF-67/Ag₃VO₄ (ZAV), was successfully synthesized using a hydrothermal technique. The optimal ZAV-30 (ZIF-67/30 wt%Ag₃VO₄) demonstrated excellent performance by degrading 98.5% of Venlafaxine (VEN) within 60 min under visible light. Extensive investigations were carried out regarding the crystal structure, morphology, composition, specific surface area, optical characteristics and electrochemical impedance. The ZAV-30 heterojunction photocatalyst outperformed bare ZIF-67 and Ag₃VO₄ photocatalysts, primarily due to enhanced photon absorption and improved charge carriers’ separation via S-scheme transfer, redox capability and high charge transfer capacity supported by electrochemical experiments and photoluminescence. The S-scheme transfer was validated by in-situ XPS measurements after light exposure. Scavenger experiments indicated that both ^•OH and ^•O₂⁻ played crucial roles as active species in the photocatalytic process. Mass spectrometry (MS) analysis of intermediates facilitated the proposal of a probable photocatalytic degradation pathway for VEN. The photoactivity of the heterojunction was influenced by a range of factors including the pH of the VEN solution, initial VEN concentration, ZAV photocatalyst dosage, and ion effects. Interestingly the ZAV-30 heterojunction exhibited superior performance in lake water, tap water and river water too. Importantly, the ZAV-30 heterojunction exhibited excellent stability and reusability, making it a promising photocatalyst.