Electron-rich biochar enhanced Z-scheme heterojunctioned bismuth tungstate/bismuth oxyiodide removing tetracycline

Photocatalytic treatment of antibiotics in aqueous ecosystems has become a promising method. However, the low efficiency photogenerated charge separation and slow kinetics of the catalyst severely limit its deployment for industrial applications. Here, the three-dimensional bismuth tungstate (Bi2WO6)/bismuth oxyiodide (BiOI) loaded on biochar (BC/BWI) composite catalyst was designed for the efficient removal of tetracycline (adsorption capacity: 227.09 mg g-1, removal rate: 99.8%). Via construction of Z-scheme heterojunctions at the interface of Bi2WO6 and BiOI, the built-in electric field promotes the directional separation of photogenerated carriers to achieve efficient separation and utilization of photogenerated charges. Meanwhile, the introduction of electron-rich biochar (BC) effectively enhances the adsorption performance, photogenerated electron migration capacity and mass transfer process of the material. The introduction of BC and the building of Z-scheme heterojunctions effectively achieve the spatially synergistic separation of photogenerated charges. The O2- dominates the photocatalytic process, according to the mechanistic studies. The degradation intermediate product testing revealed that tetracycline is efficiently degraded through two main pathways. This work provides ideas for the design of catalysts for the efficient removal of antibiotics from water bodies. In the synthesized BC/BWI catalyst, the introduction of biochar and construction of Z-type heterojunctions accelerated the photogenerated carrier separation to reach an efficient removal of tetracycline.