Characterization of visible-light photo-Fenton reactions using Fe-doped ZnS (Fex-ZnS) mesoporous microspheres

A series of Fe-doped ZnS (Fe-x-ZnS) photocatalysts were synthesized using a one-pot hydrothermal method. The physicochemical properties of the as-prepared Fe-x-ZnS microspheres were characterized by different microscopic and spectroscopic techniques. Fe doping did not obviously change the morphology and crystallinity of ZnS, but effectively broadened the light response range into the visible-light region. Degradation of p-nitrophenol (PNP) was used to evaluate the photocatalytic performance of the Fe-x-ZnS catalysts under visible light irradiation with the addition of H2O2 to facilitate photo-Fenton-like reactions. The highest PNP removal rate of 83.8% after 180 min of irradiation was achieved under the optimal conditions, including a doping ratio of 6%, a H2O2 concentration of 3 mmol L-1 and a catalyst dosage of 0.8 g L-1. The effects of aqueous/solid mass transfer and intraparticle mass transfer limitations on the PNP degradation reactions were analyzed, indicating that the variations of catalyst size caused by different Fe doping ratios did not affect the photocatalytic reactions in this study. The PNP removal mechanism of the Fe-x-ZnS photocatalyst with H2O2 addition under visible light irradiation was proposed.