Activation of PMS degradation of chlorotriazine herbicides (atrazine and simazine) by MIL101-derived Fe/Co@C under high salinity conditions

•Wide range of Cl- concentrations (1–500 mM) can effectively promote ATZ and SIM degradation.•The electron transfer at the interface was enhanced by the injection of Cl- in the Fe/Co@C/PMS system.•Two mechanisms of Cl· action in the system were proposed.•1O2, ·OH, Cl· and SO4·- coexisted, and the role of Cl· in ATZ and SIM degradation cannot be ignored. In this work, a carbon-based catalyst Fe/Co@C with MOF as a self-sacrificing template was prepared by high-temperature roasting of FeCo-MIL101, which was applied to activate PMS for the degradation of chlorotriazine herbicides (ATZ and SIM) showing excellent performance. Characterization analysis revealed that Fe/Co@C possesses a certain graphene structure and has a saturation magnetization rate of 0.87 emu/g, which can be separated from the solution easily and quickly. The degradation of ATZ and SIM was enhanced by introducing chloride ions into the system, and 100 mmol/L Cl- could lead to the complete removal of ATZ and SIM in 6 min, while improving the interfacial electron transfer of Fe/Co@C/PMS. In combination with quenching experiments, ESR test results and DFT calculations, two important roles of chlorine radicals in the reaction are proposed: (1) direct electron transfer and (2) indirect promotion of 1O2 generation through the production of HOCl. In addition, the testing of the influencing factors of the catalyst in the system (catalyst dosing, PMS dosing, pH, temperature), the testing of coexisting anions in the aqueous matrix, and the reusability all showed satisfactory performance. Finally, the degradation mechanisms of ATZ and SIM were proposed in combination with GC–MS determination of contaminant intermediates and analysis of their toxicity.