Visible-LED-light-driven photocatalytic degradation of ofloxacin and ciprofloxacin by magnetic biochar modified flower-like Bi2WO6: The synergistic effects, mechanism insights and degradation pathways

Bi2WO6 possesses good stability but poor photocatalytic activity under visible light. Herein, the coupling of Bi2WO6, Fe3O4 and biochar (Bi2WO6/Fe3O4/BC) was investigated to enhance the photocatalytic performance of Bi2WO6 through facile hydrothermal method, which almost completely degraded ofloxacin (OFL) and ciprofloxacin (CIP) within 30 min under energy-saving visible LED irradiation. The superior photocatalytic activity of Bi2WO6/Fe3O4/BC was ascribed to the stronger visible light adsorption capacity and the lower recombination of electron-hole pairs. O2− played a major role during the photocatalytic reaction. The characterization results suggested that the introduction of biochar avoided the agglomeration of Bi2WO6 microspheres and Fe3O4 nanoparticles, at the same time, the biochar participated in OFL and CIP photodegradation by consuming different oxygen-containing functional groups. In order to further evaluate the application potential of Bi2WO6/Fe3O4/BC, the effects of environment factors and the application in different actual water were carefully investigated. Various transformation products and the possible degradation pathways of OFL and CIP were analyzed based on high resolution mass spectrometry (HRMS) results, moreover, the toxicity evaluation results of Escherichia coli indicated these intermediates products were less toxic compared OFL and CIP. Overall, Bi2WO6/Fe3O4/BC can provide a potential way for the application of photocatalytic technology in ambient wastewater purification.