Kinetics and mechanism of 4-methylbenzylidene camphor degradation by UV-activated persulfate oxidation
Journal
Environmental Science and Pollution Research
Journal Volume
28
Journal Issue
14
Pages
18021-18034
Date Issued
2021
Author(s)
Abstract
4-Methylbenzylidene camphor (4-MBC), a widely used ultraviolet (UV) filter detected in various aquatic environments, has been shown to evoke estrogenic activity. In this study, the use of UV light-activated persulfate for 4-MBC degradation is evaluated for the first time. Our results showed that the combination of UV and persulfate (UV/persulfate) can significantly remove 4-MBC, with a pseudo-first-order rate constant (kobs) of 0.1349?min?1 under the conditions of [4-MBC]0?= 0.4?μM, [persulfate]0?= 12.6?μM, and initial pH = 7. The kobs and persulfate dose exhibited a linear proportional relationship in the persulfate dose range of 4.2–42?μM. The kobs remained similar at pH?5 and pH?7 but significantly decreased at pH?9. A radical scavenging test indicated that SO4?? was the dominant species in 4-MBC degradation; the second-order rate constant of SO4?? with 4-MBC was calculated to be (2.82 ± 0.05) × 109?M?1?s?1. During the UV/persulfate reaction, 4-MBC was continuously degraded, while SO4?? was gradually converted to SO42?. 4-MBC degradation involved the hydroxylation and demethylation pathways, resulting in the generation of transformation byproducts P1 (m/z 271) and P2 (m/z 243), respectively. The Microtox? acute toxicity test (Vibrio fischeri) showed increasing toxicity during the UV/persulfate degradation of 4-MBC. The 4-MBC degradation rate was markedly lower in outdoor swimming pool water than in deionized water. [Figure not available: see fulltext.] ? 2021, Springer-Verlag GmbH Germany, part of Springer Nature.
Subjects
activation energy; degradation; estrogenic compound; oxidation; radical; reaction kinetics; scavenging (chemistry); toxicity; toxicity test; transformation; ultraviolet radiation; Dryobalanops; Vibrio fischeri; 3 (4 methylbenzylidene)camphor; camphor; kinetics; oxidation reduction reaction; ultraviolet radiation; water pollutant; Camphor; Kinetics; Oxidation-Reduction; Ultraviolet Rays; Water Pollutants, Chemical
SDGs
Type
journal article