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-, OH and SO4-.