Visible-light-driven photo-Fenton reactions using Zn_1-1.5xFe_xS/g-C₃N₄ photocatalyst: Degradation kinetics and mechanisms analysis

The visible-light responsive hybrid catalysts (Zn_0.94Fe_0.04S/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 Zn_0.94Fe_0.04S 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.