New insights into the mechanism for 1O2-Dominated peroxymonosulfate activation in saline solution: In-situ generation of H2O2 to inhibit the AOX formation

[Display omitted] •The concentration of Cl− has a significant impact on the conversion of oxidative species.•The CoS@FeS catalyst can improve RhB mineralization and inhibition of the AOX formation.•The in-situ generation of H2O2 consumes HClO and thus inhibits the formation of AOX.•The H2O2 concentration related closely with the catalyst and O2 dosages. The presence of chloride ions (Cl−) in dye wastewater can hinder the peroxymonosulfate (PMS) oxidation and lead to the abundant production of toxic adsorbable organic halogens (AOX). In this study, we investigate the detailed influence of Cl− on Rhodamine B (RhB) removal and its mechanism, and propose a potential pathway for 1O2-dominated systems to inhibit AOX formation. The concentration of Cl− has a dual effect on the degradation of RhB, with low concentrations inhibiting and high concentrations promoting. Further studies have revealed that Cl− significantly impact the generation and transformation of reactive oxygen species (ROSs). EPR capturing, quenching tests, and molecular probe experiments indicate that as the Cl− concentration increases, the concentration of SO4−, OH and their contribution to the degradation of RhB gradually decrease, 1O2 slightly increase and then decrease, while HClO and chlorine radicals increase linearly. Additionally, the catalyst plays a crucial role in inhibiting AOX formation and improving the mineralization of RhB. On the one hand, introducing catalysts can alter the proportion of ROSs production. On the other hand, the in-situ generation of H2O2 on the catalyst surface, through O2 adsorption at sulfur vacancies sites, consumes the produced HClO, thereby inhibiting the formation of AOX. This study proposed a new insight into the mechanism for effective reduction of AOX content for 1O2 dominated non-radical PMS activation under saline water.