Efficient degradation of rhodamine B by magnetically separable ZnS–ZnFe₂O₄ composite with the synergistic effect from persulfate

Novel ZnS–ZnFe₂O₄ composites were successfully synthesized via a simple and green hydrothermal route. X-ray diffraction (XRD) patterns of the synthesized composite proved the presence of both ZnS and ZnFe₂O₄. The other characteristics of the composites were further characterized in detail using Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and vibrating sample magnetometry (VSM). The performance of ZnS–ZnFe₂O₄ in the presence of persulfate (PS, K₂S₂O₈) as a co-catalyst was tested for degrading rhodamine B (RhB) under UV light illumination. ZnS–ZnFe₂O₄ composites could remove about 97.67% of RhB in 90 min, which was much higher removal than either ZnS or ZnFe₂O₄ alone. Moreover, the recovery of catalyst and its recycling performance were found to be good after testing three times. A feasible mechanism analysis of RhB degradation was validated by simple classical quenching experiments. The enhanced performance was attributed to the high-efficiency separation rate of photo induced electron-hole pairs and highly active free radicals of O₂[rad]⁻, OH[rad] and SO₄[rad]⁻.