Insights into a newly discovered mechanism for 1O2 formation in a chlorine ion-mediated sulfate radical-advanced oxidation process system for levofloxacin degradation in an aqueous solution

The dual effect of chloride anions (Cl − ) on sulfate radical-advanced oxidation process (SR-AOP) systems has recently garnered increasing attention, particularly the inhibitory effects of Cl − on the degradation of organic pollutants. However, few studies have characterized the promoting effect of Cl − on SR-AOPs. Our study investigated the effect of Cl − on the degradation of levofloxacin (LVF) in peroxymonosulfate (PMS) with ZIF-67/VTM (Z-VTM) as an activator. With the addition of Cl − , singlet oxygen ( 1 O 2 ) was the dominant driver of LVF degradation in the Cl − /Z-VTM/PMS system, which differed from the dominant role of HOCl (generated from Cl − ) in the degradation of organic pollutants in previous studies. To the best of our knowledge, our study is the first to describe the conversion of HOCl to 1 O 2 in a Cl − /Z-VTM/PMS system. 1 O 2 was effectively generated in Cl − containing water at a 3.0–9.0 pH range. This work provides novel insights into the formation of ROS from HOCl during the degradation of organic pollutants in SR-AOPs, which is of great significance for the removal of organic pollutants in wastewater with high salt concentrations.