Visible light-driven Z-scheme Bi2O3/CuBi2O4 heterojunction with dual metal ions cycle for PMS activation and Lev degradation

In this study, Bi2O3/CuBi2O4 composite was prepared by sol–gel method, which was used to degrade levofloxacin (Lev) by the synergistic effect of visible light and peroxymonosulfate (PMS). The physicochemical properties of Bi2O3/CuBi2O4 were regulated by varying the molar ratio of the raw materials. The structure and morphology of the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS). Secondly, Bi2O3/CuBi2O4/Vis/PMS system was constructed to investigate the effects of different conditions (pollutant concentration, catalyst dosage, PMS concentration, pH and different anion concentration) on the removal effect of Lev. Benefit from the highly ordered alternating nanoparticles and nanosheets, Bi2O3/CuBi2O4 showed satisfactory PMS activation ability than single Bi2O3. The degradation rate increased from 12.98 ± 2.41% (Bi2O3) to 70.62 ± 0.07% (Bi2O3/CuBi2O4) within 120 min. Finally, the quenching experiments and electron paramagnetic resonance (EPR) results showed that radical pathways (h+, SO4-·, ·OH) and non-radical pathways (1O2) were both involved in the PMS activation process. The main reaction mechanism of Bi2O3/CuBi2O4/Vis/PMS system was predicted, the unique electron transfer pathway of Z-scheme heterojunction and Cu(II)/Cu(I), Bi(V)/Bi(III) redox-cycle on the catalyst surface effectively drove the generation of radicals, realizing the high efficiency of pollutant degradation.