Efficient removal of triclosan via peroxymonosulfate activated by a ppb level dosage of Co(II) in water: Reaction kinetics, mechanisms and detoxification

Triclosan (TCS), an extensively used broad-spectrum antimicrobial agent, has raised significant environmental concerns regarding its widespread occurrence in waters. In this study, the removal of TCS in aqueous solution via peroxymonosulfate (PMS) activated by an extremely low-level Co2+ (0.02 μM) was systematically investigated. During preliminary test, TCS (10 μM) was totally degraded in 30 min by using 0.1 μM Co2+ and 40 μM PMS at pH 7.0 with a degradation rate constant of 0.1219 min−1. A first-order apparent degradation rate of TCS was found with respect to the PMS concentrations. At extremely low dosage of Co2+ (0.02 μM), the presence of NO3−, HCO3−, PLFA, and SRHA within test concentrations significantly inhibited TCS removal, while a dual effect of Cl− on the degradation rate of TCS was observed. The quenching experiments verified that SO4- was the dominant reactive oxygen species (ROS) rather than OH. Six major intermediates were identified using TOF-LC-MS, based on which we proposed three associated reaction pathways including hydroxylation, ether bond breakage, and dechlorination. Toxicity predictions by ECOSAR software exhibited aquatic toxicity reduction of TCS after Co2+/PMS treatment. We outlook these findings to advance the feasibility of organic contaminants removal via Co2+/PMS system with Co2+ at extremely low levels. [Display omitted] •Efficient degradation of TCS was achieved by ppb-level Co2+ activated PMS.•SO4- dominated the TCS degradation process at neutral condition.•Cl− exhibited a dual effect on TCS removal at low and high concentrations.•Six intermediates identified and three main reaction pathways were proposed.