Peroxymonosulfate activation by porous BiFeO3 for the degradation of bisphenol AF: Non-radical and radical mechanism

In this study, porous BiFeO3 (BFO) was successfully synthesized by sol-gel method and employed as an activator for peroxymonosulfate (PMS) to degrade bisphenol AF (BPAF), an emerging contaminant in the water. Porous BFO were prepared and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and oxygen temperature programmed desorption (O-2-TPD). Compared to the raw BFO, large improvement of BPAF removal was observed when using porous BFO to activate PMS. The influences of selected activating systems, PMS dosage, catalysts loading, initial pH and water matrix on the degradation efficiency were examined. The role of reactive oxygen species produced in the degradation process of BPAF were identified through chemical quenching experiments and electron spin resonance (ESR), which demonstrated that high performance of porous BFO/PMS on BPAF removal was ascribed to the co-oxidation of radicals (sulfate radical and hydroxyl radical) and non-radical reactive oxygen species (singlet oxygen). Based on the XPS and ESR results, this study proved that lattice oxygen on the surface of BFO participated in the formation of singlet oxygen and the oxygen vacancies were propitious for the catalytic degradation. The reaction pathways and the mechanism of BPAF degradation via the BFO/PMS system were also proposed.