Degradation behavior of triclosan by co-exposure to chlorine dioxide and UV irradiation: influencing factors and toxicity changes
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This study investigated the transformation of triclosan (TCS) following co-exposure to UV irradiation and ClO2. Special attention was given to understand the influencing of water quality parameters and toxicity changes during the co-exposure process. The results show that the co-exposure process prompted TCS elimination quickly and effectively, with more than 99% of TCS degraded under the experimental conditions. The molar yield ratios of 2,4-dichlorophenol/TCS (2,4-DCP/TCS) were calculated to be 35.81–74.49%; however, the by-product of 2,8-dichlorodibenzop-dioxin (2,8-Cl2DD) was not detected. The TCS degradation was sensitive to ClO2 dosage, pH, H2O2, and natural organic matter (NOM), but not to the carbonate (CO32−) concentration. Neutral and slightly alkaline condition were favorable to TCS elimination. The TCS removal rate increased from 85.33 to 99.75% when the ClO2 concentration increased from 0.25 to 1.5 mg L−1. TCS degradation can be promoted at low NOM level (1, 3, and 5 mg L−1), whereas was inhibited at high NOM concentrations of 7 and 9 mg L−1. While adding H2O2, the degradation rate of TCS increased with increasing H2O2 concentration from 1 to 3 mg L−1; however, too low or overdosed H2O2 (0.5 and 5 mg L−1) hindered TCS degradation. Based on the results of a microtox bioassay, the toxicity did not change following the co-exposure process.
KeywordsUV Chlorine dioxide (ClO2) Triclosan Co-exposure Toxicity
This study was supported in part by the National Natural Science Foundation of China (Grant Nos. 51378446, 51678527, 51408518), the Guiding Project of Fujian Province of China (No. 2017Y0079), the Natural Science Foundation of Fujian Province of China (No. 2016J01695), New Century Excellent Talents in Fujian Province University (JA14227), and the Science and Technology Bureau of Xiamen (3502Z20131157, 3502Z20150051).
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