Enhanced treatment of high chloride organic wastewater under lower peroxymonosulfate consumption: A pathway for the formation of Fe(IV)=O excited by chloride ions

The inhibition of oxidation efficiency and the formation of toxic chlorinated organic byproducts owing to Cl still represent a significant threat to the treatment of high chloride organic wastewater using advanced oxidation processes. This study explores new pathways for utilizing Cl to promote the formation of Fe(Ⅳ)=O by single atom Fe-CNs catalysts under peroxymonosulfate (PMS) system, which significantly increases sulfamethoxazole (SMX) degradation rate constant by 2.97 times, enhances PMS utilization efficiency (reducing by 92 % PMS consumption) and simultaneously avoids the formation of chlorinated organic byproducts. Experiments and theoretical calculation revealed that the in-situ generated HClO (generated via the reaction of PMS and Cl) more easily reacts with Fe–pyridinic N active sites of Fe-CNs catalysts to generate Fe(Ⅳ)=O through a lower-energy-barrier pathway, rather than directly oxidates pollutants. This study provides an approach to utilize omnipresent Cl achieving high efficiency, high selectivity, low PMS consumption and harmless treatment for chloride-containing organic wastewaters.