Novel UV-LED-driven photocatalysis-chlorine activation for carbamazepine degradation by sulfur-doped NH2-MIL 53 (Fe) composites: Electronic modulation effect and the dual role of chlorine
Lei Wang, Huiming Zheng, Chenkai Hu, Hanxuan Zeng, Xiaoyan Ma, Qingsong Li, Xueyan Li, Shiqing Zhou, Jing Deng
Abstract
Chlorine activation-inefficient and the generation of disinfection by-products (DBPs) has indeed limited the application of UV/chlorine process. In this study, the typical metal-organic frameworks (MOFs) NH 2 -MIL53(Fe) were successfully modified with organic ligands containing sulfur functional groups and applied to construct a novel UV-LED-driven heterogeneous chlorine activation system. The generation of intermediate energy levels and the charge redistribution effect on Fe-S bond facilitated the excitation of electrons and realized the effective separation of photohole (h vb + ) and photoelectron (e cb - ). The involvement of S-NH 2 -MIL53(Fe) improved the efficiency of UV-LED/chlorine process by 6 times. The effective activation of HOCl/OCl - by h vb + and e cb - significantly enhanced the yield of HO · and Cl · . More importantly, HOCl/OCl - played a dual role in UV-LED/chlorine/S-NH 2 -MIL53(Fe) process as a precursor for the generation of free radicals and a catalyst for the enhancement of HO · yield, which could achieve efficient removal of the target pollutants at lower chlorine doses. In addition, the presence of low-valent sulfur species and e cb - accelerated the cycle of Fe(II)/Fe(III) and in-situ generation of HO · and Cl · . The known generation of DBPs in UV-LED/chlorine/S-NH 2 -MIL53(Fe) process decreased by 37.9% compared to UV-LED/chlorine process. Developing novel UV-LED/chlorine/S-NH 2 -MIL53(Fe) processes provided a reliable strategy to efficiently purify actual micro-polluted water bodies.