"Small amount for multiple times" of H_(2)O_(2) feeding way in MoS_(2)-Fex heterogeneous fenton for enhancing sulfadiazine degradation

In recent years, MoS_(2) 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 H_(2)O_(2) feeding way on the whole Fenton process. Here, we report a new type of composite catalyst (MoS_(2)-Fe_(x)) prepared in a simple way with highly dispersed iron to provide more active sites. MoS_(2)-Fe_(x) was proved to possess selectivity for singlet oxygen (^(1)O_(2)) in effectively degrading sulfadiazine with a wide pH adaptability (4.0~10.0). Importantly, the mechanism of the interaction between H_(2)O_(2) and MoS_(2) 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 H_(2)O_(2), the “small amount for multiple times” of H_(2)O_(2) feeding way can increase the degradation rate of sulfadiazine from 36.9% to 91.1% in the MoS_(2)-Fe_(x) heterogeneous Fenton system. It is demonstrated that the “small amount for multiple times” of H_(2)O_(2) feeding way can reduce the side reaction of decomposition of H_(2)O_(2) by MoS_(2) and effectively improve the utilization rate of H_(2)O_(2) and the stability of MoS_(2)-Fe_(x). Compared with Fe_(2)O_(3)^(-)based Fenton system, MoS_(2)-Fe_(x) can significantly save the amount of H_(2)O_(2). Compared with nano-iron powder, the formation of iron sludge in MoS_(2)-Fe_(x) system was significantly reduced. Furthermore, long-term degradation test showed that the MoS_(2)-Fe75/H_(2)O_(2) 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.