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@article{1840486,
author = {Remke, Stephanie C. and Bürgin, Tobias H. and Ludvíková, Lucie and Heger, Dominik and Wenger, Oliver S. and von Gunten, Urs and Canonica, Silvio},
article_number = {April},
doi = {http://dx.doi.org/10.1016/j.watres.2022.118095},
keywords = {Aquatic photochemistry; Phototransformation; Organic contaminant; Dissolved organic matter; Long-lived photooxidants},
language = {eng},
issn = {0043-1354},
journal = {Water Research},
title = {Photochemical oxidation of phenols and anilines mediated by phenoxyl radicals in aqueous solution},
url = {https://www.sciencedirect.com/science/article/pii/S0043135422000586},
volume = {213},
year = {2022}
}
TY - JOUR
ID - 1840486
AU - Remke, Stephanie C. - Bürgin, Tobias H. - Ludvíková, Lucie - Heger, Dominik - Wenger, Oliver S. - von Gunten, Urs - Canonica, Silvio
PY - 2022
TI - Photochemical oxidation of phenols and anilines mediated by phenoxyl radicals in aqueous solution
JF - Water Research
VL - 213
IS - April
SP - 1-11
EP - 1-11
PB - Elsevier Ltd
SN - 00431354
KW - Aquatic photochemistry
KW - Phototransformation
KW - Organic contaminant
KW - Dissolved organic matter
KW - Long-lived photooxidants
UR - https://www.sciencedirect.com/science/article/pii/S0043135422000586
N2 - Reactive intermediates formed upon irradiation of chromophoric dissolved organic matter (CDOM) contribute to the degradation of various organic contaminants in surface waters. Besides well-studied “short-lived” photooxidants, such as triplet state CDOM (3CDOM*) or singlet oxygen, CDOM-derived “long-lived” photooxidants (LLPO) have been suggested as key players in the transformation of electron-rich contaminants. LLPO were hypothesized to mainly consist of phenoxyl radicals derived from phenolic moieties in the CDOM. To test this hypothesis and to better characterize LLPO, the transformation kinetics of selected target compounds (phenols and anilines) induced by a suite of electron-poor model phenoxyl radicals was studied in aerated aqueous solution at pH 8. The phenoxyl radicals were generated by photosensitized oxidation of the parent phenols using aromatic ketones as photosensitizers. Under steady-state irradiation, the presence of any of the electron-poor phenols lead to an enhanced abatement of the phenolic target compounds (at an initial concentration of 1.0 × 10−7 M) compared to solutions containing the photosensitizer but no electron-poor phenol. A trend of increasing reactivity with increasing one-electron reduction potential of the electron-poor phenoxyl radical (range: 0.85‒1.12 V vs. standard hydrogen electrode) was observed. Using the excited triplet state of 2-acetonaphthone as a selective oxidant for phenols, it was observed that the reactivity correlated with the concentration of electron-poor phenoxide present in solution. The rates of transformation of anilines induced by the 4-cyanophenoxyl radical were an order of magnitude smaller than for the phenolic target compounds. This was interpreted as a reduction of the radical intermediates back to the parent compound by the superoxide radical anion. Laser flash photolysis measurements confirmed the formation of the 4-cyanophenoxyl radical in solutions containing 2-acetonaphthone and 4-cyanophenol, and yielded values of (2.6 − 5.3) × 108 M−1 s−1 for the second-order rate constant for the reaction of this radical with 2,4,6-trimethylphenol. These and further results indicate that electron-poor model phenoxyl radicals generated through photosensitized oxidation are useful models to understand the photoreactivity of LLPO as part of the CDOM.
ER -
REMKE, Stephanie C., Tobias H. BÜRGIN, Lucie LUDVÍKOVÁ, Dominik HEGER, Oliver S. WENGER, Urs VON GUNTEN a Silvio CANONICA. Photochemical oxidation of phenols and anilines mediated by phenoxyl radicals in aqueous solution. \textit{Water Research}. Elsevier Ltd, 2022, roč.~213, April, s.~1-11. ISSN~0043-1354. Dostupné z: https://dx.doi.org/10.1016/j.watres.2022.118095.
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