The degradation of triclosan (TCS) by UV/H2O2 was investigated in this paper. The effects of H2O2 dose, pH, common inorganic anions (e.g., HCO3-, Cl-, NO3- and SO42-) and natural organic matter (NOM) on the removal of TCS were also evaluated. Finally, the degradation products and transformation mechanism of TCS by UV/H2O2 were studied. The results showed that the degradation of TCS in UV/H2O2 system followed the pseudo first-order kinetics. The degradation efficiency of TCS enhanced gradually with the increase in H2O2 dose, while excess H2O2 could compete with TCS for hydroxyl radical (HO·). The degradation efficiency of TCS at pH 8.5 was higher than those at other studied pH values (i.e., pH 5.3-7.4). Though HCO3- is a common scavenger of HO·, it had little influence on the degradation of TCS, while the other inorganic anions including Cl-, NO3- and SO42- could hardly affect the removal of TCS. The presence of NOM could inhibit TCS degradation and the inhibiting effect enhanced with the increase in the concentration of NOM. Compared with the removal of TCS in pure water, its degradation in real waters was inhibited because of the competition of HCO3- and NOM in real waters with TCS for HO·. Twenty-six degradation products of TCS were detected using a ultra-high definition accurate-mass quadrupole time-of-flight tandem mass spectrometer coupled with a high performance liquid spectrometer (LC-QTOF/MS). Based on these identified reaction products, the possible transformation mechanism of TCS by UV/H2O2 was proposed revealing six different degradation pathways, including dechlorination-hydrogenation, dechlorination-hydroxylation, hydroxylation, dehydrogenation, cyclization and ether cleavage.
付永胜, 史鸿乐, 刘义青, 周高峰. UV/H2O2光化学降解水中的三氯生[J]. 中国环境科学, 2018, 38(2): 616-626.
FU Yong-sheng, SHI Hong-le, LIU Yi-qing, Zhou Gao-feng. Photochemical degradation of triclosan by UV/H2O2 in water. CHINA ENVIRONMENTAL SCIENCECE, 2018, 38(2): 616-626.
Gao Y, Ji Y, Li G, et al. Mechanism, kinetics and toxicity assessment of OH-initiated transformation of triclosan in aquatic environments[J]. Water Research, 2014,49(2):360-370.
[2]
Chen X J, Richard J, Liu Y L, et al. Ozonation products of triclosan in advanced wastewater treatment[J]. Water Research, 2012,46(7):2247-2256.
[3]
Wilson B A, Smith V H, Denoyelles F, et al. Effects of three pharmaceutical and personal care products on natural freshwater algal assemblages[J]. Environmental Science & Technology, 2003,37(9):1713-1719.
[4]
Liang X M, Nie X P, Ying G G, et al. Assessment of toxic effects of triclosan on the swordtail fish (Xiphophorus helleri) by a multi-biomarker approach[J]. Chemosphere, 2013,90(3):1281-1288.
[5]
Geens T, Neels H, Govaci A. Distribution of bisphenol-A, triclosan and n-nonylphenol in human adipose tissue, liver and brain[J]. Chemosphere, 2012,87(7):796-802.
[6]
Ishibashi H, Matsumura N, Hirano M, et al. Effects of triclosan on the early life stages and reproduction of medaka Oryzias Iatipes and induction of hepatic vitellogenin[J]. Aquatic Toxicology, 2004,67(2):167-179.
[7]
Gee R H, Charles A, Taylor N, et al. Oestrogenic and androgenic activity of triclosan in breast cancer cells[J]. Journal of Applied Toxicology, 2008,28(1):78-91.
Shah N S, He X, Khan H M, et al. Efficient removal of endosulfan from aqueous solution by UV-C/peroxides:a comparative study[J]. Journal of Hazardous Materials, 2013,263(2):584-592.
Liu Y, He X, Fu Y, et al. Degradation kinetics and mechanism of oxytetracycline by hydroxyl radical-based advanced oxidation processes[J]. Chemical Engineering Journal, 2016,284:1317-1327.
[14]
Kliegman S, Eustis S N, Arnold W A, et al. Experimental and theoretical insights into the involvement of radicals in triclosan phototransformation[J]. Environmental Science & Technology, 2013,47(13):6756-6763.
[15]
He X, Pelaez M, Westrick J A, et al. Efficient removal of microcystin-LR by UV-C/H2O2 in synthetic and natural water samples[J]. Water Research, 2012,46(5):1501-1510.
[16]
Canonica S, Kohn T, Mac M, et al. Photosensitizer method to determine rate constants for the reaction of carbonate radical with organic compounds[J]. Environmental Science & Technology, 2005,39(23):9182-9188.
[17]
Liao C H, Kang S F, Wu F A. Hydroxyl radical scavenging role of chloride and bicarbonate ions in the H2O2/UV process[J]. Chemosphere, 2001,44(5):1193-1200.
[18]
Neta P, Huie R E, Ross A B. Rate constants for reactions of inorganic radicals in aqueous solution[J]. Journal of Physical and Chemical Reference Data, 1988,17(3):1027-1284.
[19]
Mark G, Korth H G, Schuchmann H P, et al. The photochemistry of aqueous nitrate ion revisited[J]. Journal of Photochemistry and Photobiology A:Chemistry, 1996,101(2/3):89-103.
[20]
Baxendale J H, Wilson J A. The photolysis of hydrogen peroxide at high light intensities[J]. Transactions of the Faraday Society, 1957,53:344-356.
[21]
Keen O S, Love N G, Linden K G. The role of effluent nitrate in trace organic chemical oxidation during UV disinfection[J]. Water Research, 2012,46(16):5224-5234.
[22]
Liao C H, Gurol M D. Chemical oxidation by photolytic decomposition of hydrogen peroxide[J]. Environmental Science & Technology, 1995,29(12):3007-3014.
[23]
Westerhoff P, Mezyk S P, Cooper W J, et al. Electron pulse radiolysis determination of hydroxyl radical rate constants with Suwannee River fulvic acid and other dissolved organic matter isolates[J]. Environmental Science & Technology, 2007,41(13):4640-4646.
[24]
Latch D E, Packer J L, Arnold W A, et al. Photochemical conversion of triclosan to 2,8-dichlorodibenzo-p-dioxin in aqueous solution[J]. Journal of Photochemistry and Photobiology A:Chemistry, 2003,158(1):63-66.
