Visible-light-driven photo-Fenton reactions using Zn1-1.5Fe S/g-C3N4 photocatalyst: Degradation kinetics and mechanisms analysis

The visible-light responsive hybrid catalysts (Zn0.94Fe0.04S/g-C3N4 or ZCN) were synthesized by a rapid microwave hydrothermal method. Our results showed that the deposition of Fe-doped ZnS onto g-C3N4 sheets prevented the aggregation of Zn0.94Fe0.04S and increased the surface area for mass transfer and light absorption. The highest degradation rate of p-nitrophenol (PNP) was 96.0% and the total organic carbon removal rate was 55.4% after 60-min simulated solar light irradiation on ZCN with Fe doping and g-C3N4 loading ratios of 0.04 and 0.20, respectively. Hydroxyl radical played a dominant role in PNP degradation, which was primarily attributed to the photo-Fenton reactions. The PNP degradation pathway involved denitration and hydroxylation reactions according to the Density Function Theory calculations and HPLC-MS/MS results. The QSAR analysis indicated that the toxicity of most intermediates was lower than PNP. This study develops novel materials with superior photocatalytic activity for elimination of refractory organic pollutants in wastewater.