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Degradation and Defluorination of Per- and Polyfluoroalkyl Substances by Direct Photolysis at 222 nm
https://orcid.org/0000-0003-4942-3541
https://orcid.org/0000-0002-8838-4269
https://orcid.org/0000-0002-3786-094X
The susceptibility of 19 representative per- and polyfluoroalkyl substances (PFAS) to direct photolysis and defluorination under far-UVC 222 nm irradiation was investigated. Enhanced photolysis occurred for perfluorocarboxylic acids (PFCAs), fluorotelomer unsaturated carboxylic acids (FTUCAs), and GenX, compared to that at conventional 254 nm irradiation on a similar fluence basis, while other PFAS showed minimal decay. For degradable PFAS, up to 81% of parent compound decay (photolysis rate constant (k 222 nm) = 8.19–34.76 L·Einstein–1; quantum yield (Φ222 nm) = 0.031–0.158) and up to 31% of defluorination were achieved within 4 h, and the major transformation products were shorter-chain PFCAs. Solution pH, dissolved oxygen, carbonate, phosphate, chloride, and humic acids had mild impacts, while nitrate significantly affected PFAS photolysis/defluorination at 222 nm. Decarboxylation is a crucial step of photolytic decay. The slower degradation of short-chain PFCAs than long-chain ones is related to molar absorptivity and may also be influenced by chain-length dependent structural factors, such as differences in pK a, conformation, and perfluoroalkyl radical stability. Meanwhile, theoretical calculations indicated that the widely proposed HF elimination from the alcohol intermediate (C n F2n+1OH) of PFCA is an unlikely degradation pathway due to high activation barriers. These new findings are useful for further development of far-UVC technology for PFAS in water treatment.
Far-UVC 222 nm irradiation is capable of degrading groups of PFAS including PFCAs, FTUCAs, and GenX, and the photolysis rate and extent are influenced by molar absorptivity and possibly several chain-length-dependent structural factors.
Degradation and Defluorination of Per- and Polyfluoroalkyl Substances by Direct Photolysis at 222 nm
https://orcid.org/0000-0003-4942-3541
https://orcid.org/0000-0002-8838-4269
https://orcid.org/0000-0002-3786-094X
The susceptibility of 19 representative per- and polyfluoroalkyl substances (PFAS) to direct photolysis and defluorination under far-UVC 222 nm irradiation was investigated. Enhanced photolysis occurred for perfluorocarboxylic acids (PFCAs), fluorotelomer unsaturated carboxylic acids (FTUCAs), and GenX, compared to that at conventional 254 nm irradiation on a similar fluence basis, while other PFAS showed minimal decay. For degradable PFAS, up to 81% of parent compound decay (photolysis rate constant (k 222 nm) = 8.19–34.76 L·Einstein–1; quantum yield (Φ222 nm) = 0.031–0.158) and up to 31% of defluorination were achieved within 4 h, and the major transformation products were shorter-chain PFCAs. Solution pH, dissolved oxygen, carbonate, phosphate, chloride, and humic acids had mild impacts, while nitrate significantly affected PFAS photolysis/defluorination at 222 nm. Decarboxylation is a crucial step of photolytic decay. The slower degradation of short-chain PFCAs than long-chain ones is related to molar absorptivity and may also be influenced by chain-length dependent structural factors, such as differences in pK a, conformation, and perfluoroalkyl radical stability. Meanwhile, theoretical calculations indicated that the widely proposed HF elimination from the alcohol intermediate (C n F2n+1OH) of PFCA is an unlikely degradation pathway due to high activation barriers. These new findings are useful for further development of far-UVC technology for PFAS in water treatment.
Far-UVC 222 nm irradiation is capable of degrading groups of PFAS including PFCAs, FTUCAs, and GenX, and the photolysis rate and extent are influenced by molar absorptivity and possibly several chain-length-dependent structural factors.
Degradation and Defluorination of Per- and Polyfluoroalkyl Substances by Direct Photolysis at 222 nm
https://orcid.org/0000-0003-4942-3541
https://orcid.org/0000-0002-8838-4269
https://orcid.org/0000-0002-3786-094X
The susceptibility of 19 representative per- and polyfluoroalkyl substances (PFAS) to direct photolysis and defluorination under far-UVC 222 nm irradiation was investigated. Enhanced photolysis occurred for perfluorocarboxylic acids (PFCAs), fluorotelomer unsaturated carboxylic acids (FTUCAs), and GenX, compared to that at conventional 254 nm irradiation on a similar fluence basis, while other PFAS showed minimal decay. For degradable PFAS, up to 81% of parent compound decay (photolysis rate constant (k 222 nm) = 8.19–34.76 L·Einstein–1; quantum yield (Φ222 nm) = 0.031–0.158) and up to 31% of defluorination were achieved within 4 h, and the major transformation products were shorter-chain PFCAs. Solution pH, dissolved oxygen, carbonate, phosphate, chloride, and humic acids had mild impacts, while nitrate significantly affected PFAS photolysis/defluorination at 222 nm. Decarboxylation is a crucial step of photolytic decay. The slower degradation of short-chain PFCAs than long-chain ones is related to molar absorptivity and may also be influenced by chain-length dependent structural factors, such as differences in pK a, conformation, and perfluoroalkyl radical stability. Meanwhile, theoretical calculations indicated that the widely proposed HF elimination from the alcohol intermediate (C n F2n+1OH) of PFCA is an unlikely degradation pathway due to high activation barriers. These new findings are useful for further development of far-UVC technology for PFAS in water treatment.
Far-UVC 222 nm irradiation is capable of degrading groups of PFAS including PFCAs, FTUCAs, and GenX, and the photolysis rate and extent are influenced by molar absorptivity and possibly several chain-length-dependent structural factors.
Degradation and Defluorination of Per- and Polyfluoroalkyl Substances by Direct Photolysis at 222 nm
Xin, Xiaoyue (Autor:in) / Kim, Juhee (Autor:in) / Ashley, Daniel C. (Autor:in) / Huang, Ching-Hua (Autor:in)
ACS ES&T Water ; 3 ; 2776-2785
11.08.2023
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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