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 Co ²⁺ (0.02 μM) was systematically investigated. During preliminary test, TCS (10 μM) was totally degraded in 30 min by using 0.1 μM Co ²⁺ 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 Co ²⁺ (0.02 μM), the presence of NO ₃ ^- , HCO ₃ ^- , 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 SO ₄ ^- 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 Co ²⁺ /PMS treatment. We outlook these findings to advance the feasibility of organic contaminants removal via Co ²⁺ /PMS system with Co ²⁺ at extremely low levels.
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