“Small amount for multiple times” of H2O2 feeding way in MoS2-Fex heterogeneous fenton for enhancing sulfadiazine degradation

In recent years, MoS2 catalyzed/cocatalyzed Fenton/Fenton-like systems have attracted wide attention in the field of pollution control, but there are few studies on the effect of H2O2 feeding way on the whole Fenton process. Here, we report a new type of composite catalyst (MoS2-Fex) prepared in a simple way with highly dispersed iron to provide more active sites. MoS2-Fex was proved to possess selectivity for singlet oxygen (1O2) in effectively degrading sulfadiazine with a wide pH adaptability (4.0∼10.0). Importantly, the mechanism of the interaction between H2O2 and MoS2 on the Fenton reaction activity was revealed through the combination of experiment and density functional theory (DFT) calculations. Compared to the traditional “a large amount for one time” feeding way of H2O2, the “small amount for multiple times” of H2O2 feeding way can increase the degradation rate of sulfadiazine from 36.9% to 91.1% in the MoS2-Fex heterogeneous Fenton system. It is demonstrated that the “small amount for multiple times” of H2O2 feeding way can reduce the side reaction of decomposition of H2O2 by MoS2 and effectively improve the utilization rate of H2O2 and the stability of MoS2-Fex. Compared with Fe2O3-based Fenton system, MoS2-Fex can significantly save the amount of H2O2. Compared with nano-iron powder, the formation of iron sludge in MoS2-Fex system was significantly reduced. Furthermore, long-term degradation test showed that the MoS2-Fe75/H2O2 system could maintain the effectiveness of degrading organic pollutants for 10 days (or even longer). This study has a guiding significance for the large-scale treatment of industrial wastewater by improved Fenton technology in the future.