[Degradation of Triclosan by Heat Activated Persulfate Oxidation]

Sulfate radical (SO₄^·-)-based advanced oxidation technologies (SR-AOPs) are widely used for remediation of contaminated groundwater and soils. This study investigated the reaction kinetics, products, and transformation pathways of triclosan, a widely used antimicrobial agent, during its degradation by heat activated persulfate oxidation. Experimental results revealed that increasing temperature or initial persulfate concentration significantly enhanced the degradation of triclosan. The reaction could be fitted in the pseudo-first-order kinetic model and the activation energy (E_a) was determined to be 142 kJ·mol^-1. The presence of humic acid markedly inhibited triclosan degradation, whereas chloride (Cl^-) showed a more complicated effect. Triclosan degradation was slightly accelerated in the presence of 5 μmol·L^-1 Cl^-, however, a higher concentration of Cl^- (e.g., 10 μmol·L^-1) showed an inhibitory effect. Using liquid chromatography-mass spectrometry, a total of six transformation products, including 4-chlorocatechol, 2,4-dichlorophenol, and 2-chloro-5-(2,4-dichloro-6-hydroxyphenoxy)-1,4-benzoquinone, were identified. Accordingly, the cleavage of the ether bond and hydroxylation of the phenol ring were proposed as the principal pathways of triclosan degradation upon reaction with SO₄^·-. The findings of this study can be used to evaluate the feasibility of decontamination of triclosan by SR-AOPs.