Improved photocatalytic property of ZnO by simultaneously integrating with Ag3VO4 for constructing a heterojunction and biochar as charge transfer bridge via microwave hydrothermal method

In this work, a hierarchical Ag3VO4/ZnO/BC composite (abbreviated as AZB) is firstly prepared via a microwave-assisted solvothermal strategy and used as photocatalyst to degrade levofloxacin (LFX) under visible-light irradiation. After optimizing the mass ratio of components and the photoreaction operation parameters, the optimal 0.2Ag3VO4/ZnO/0.1BC (denoted as A0.2ZB0.1) endows the superior photocatalytic removal rate toward LFX (10 mg/L) up to 91.2% at 120 min, revealing approximately 10 times enhancement than that of ZnO (9.4%). Meanwhile, the A0.2ZB0.1 displays desirable reusability and stability after cycling 5 cycles and the •O2- and h+ are the dominating reactive species during photocatalysis process. The improved photocatalytic performance can be primarily attributed to successful establishment of a heterojunction with n-n scheme between ZnO and Ag3VO4. This leads to enhanced responsive capability to visible light and increased separation and transmission efficiency of the photogenerated electron/hole (e-/h+) pairs. Furthermore, the biochar (BC) with excellent conductivity can act as a charge-transfer bridge for further accelerating the charges transfer in composite. In addition, the analysis of intermediates identified through liquid chromatography-mass spectrometry (LC-MS) allowed for a reasonable inference for the potential mechanism and pathway involved in photodegradation. Overall, our study demonstrates an innovative strategy to enhance the photocatalytic activity of ZnO through the simultaneous incorporation of BC and the creation of a heterojunction composite.