Norfloxacin Degradation\nby Persulfate Activated with\nCu₂O@WO₃ Composites: Efficiency, Stability,\nMechanism, and Degradation Pathway

Abstract

Tungsten trioxide and cuprous oxide composites were successfully\nprepared by the solvothermal and coprecipitation method. The obtained\ncomposites were comprehensively characterized using scanning electron\nmicroscopy (SEM), X-ray diffraction (XRD), Fourier transform-infrared\nspectroscopy (FT-IR), Raman, and PL spectroscopy. The Cu₂O@WO₃/PS system was developed to degrade norfloxacin (NOR)\nin an aqueous solution. The photodegradation experiments and electrochemical\ncharacterization (EIS and photocurrent curves) showed that Cu₂O@WO₃(2–1) exhibited optimal photocatalytic\nactivity under visible light. Furthermore, the sulfate radical was\ncorroborated to play a predominant role in the photodegradation process,\nand the possible free radical formation mechanism was put forward.\nDensity functional theory (DFT) calculation and LC-MS were utilized\nto investigate the intermediates during NOR degradation, and three\npossible degradation pathways were elucidated. Ecotoxicity analysis\nby TEST showed that the toxicity of these intermediates was generally\nweaker than parent NOR. Moreover, the synthetic sample was authenticated\nto possess good stability and repeatability. This work provided the\nguidance for available and applicable utilization of persulfate photocatalytic\nactivation technology in pharmaceutical wastewater purification.