UV-LED-driven photocatalytic chlorine activation with typical spinel ferrites for carbamazepine degradation: Critical role of superoxide radicals, disinfection by-product formation and toxicity evaluation

Chlorine activation-inefficiency and the generation of disinfection by-products (DBPs) have indeed limited the application of the UV/chlorine process. In this study, zinc ferrite nanorods (ZFO-R) with excellent photovoltaic properties were successfully prepared for the construction of a novel heterogeneous UV-LED-driven chlorine activation system. The addition of ZFO-R increased the first-order reaction rate constant for the degradation of carbamazepine (CBZ) by the UV-LED/chlorine process by 6 times. Mechanism investigation indicated that superoxide radicals (O 2 − ) dominated the generation of hydroxyl radicals (HO ) and chlorine radicals (Cl ) in the system by promoting the activation of HClO/ClO − , and the increased yields of HO and Cl enhanced their contribution to the degradation of the target pollutants. Importantly, the efficient activation of chlorine not only promoted the generation of reactive species but also inhibited the formation of DBPs by shorting the contact time between chlorine and precursors, which effectively controlled the toxicity of the reaction system. This work proposes a reliable strategy for inhibiting DBPs formation in the UV/chlorine process and broadens the application of spinel ferrites in environmental remediation, achieving efficient and reliable purification of actual micropolluted water bodies.