Mechanism insights into the enhanced photocatatlytic peroxydisulfate activation by Fe3O4/BiOI heterojunction

Combining various advanced oxidation processes has been considered as an emerging approach for degrading organic contaminants, which can overcome the deficiencies of a single one. In this study, the photocatalytic oxidation and persulfate-based oxidation were allied for degrading high-concentration Rhodamine B (RhB). To strengthen this alliance, Fe3O4/BiOI p-n heterojunctions were constructed by anchoring Fe3O4 nanoparticles onto flower-like BiOI. Various instrumental techniques, including X-ray diffractometer, field emission scanning electron microscope, transmission electron microscope, X-ray photoelectron spectrometer, photoluminescence emission spectroscopy, UV–Vis diffuse reflectance spectrometer, vibrating sample magnetometer and surface area analyzer were used to characterize these heterojunctions. 100 mg·L−1 RhB was utilized as the probing target to appraise the photocatalytic peroxydisulfate activation by Fe3O4/BiOI heterojunction under visible light illumination. The pseudo-first-order kinetic model could well describe the RhB degradation process. Finally, the mechanism on the photocatalytic peroxydisulfate activation over Fe3O4/BiOI heterojunction was proposed and discussed.