Thermal Decomposition of Anionic, Zwitterionic, and Cationic Polyfluoroalkyl Substances in Aqueous Film-Forming Foams
Thermal Decomposition of Anionic, Zwitterionic, and Cationic Polyfluoroalkyl Substances in Aqueous Film-Forming Foams
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水成膜泡沫中阴离子、两性离子和阳离子多氟烷基物质的热分解
DOI：
10.1021/acs.est.1c02125
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发表时间：
2021
影响因子：
11.4
通讯作者：
Spoto, Anthony
中科院分区：
文献类型：
--
作者：
Xiao, Feng;Sasi, Pavankumar Challa;Alinezhad, Ali;Golovko, Svetlana A.;Golovko, Mikhail Y.;Spoto, Anthony
在这项研究中，我们研究了阳离子、两性离子和阴离子多氟烷基物质的热分解机制，包括那些存在于水成膜泡沫（AFFF）样品中的物质。我们提出了新的证据，证明多氟烷基物质在热处理过程中给出了不同链长的全氟烷基物质的定量产率。研究结果支持自由基介导的转化机制，包括随机链断裂和端链断裂，导致某些多氟烷基酰胺和磺胺形成全氟辛酸（PFOA）等全氟烷基羧酸。我们的研究结果还支持了多氟烷基磺酰胺非氟化部分的直接热分解机制（链剥离），从而形成全氟辛烷磺酸（PFOS）和其他结构相关的多氟烷基化合物。8:2氟端聚物磺酸通过端链断裂和重组反应进行热分解，依次生成全氟辛烷磺酸。所有研究的多氟烷基物质在200-300°C时开始降解，在≥400°C时几乎完全分解。利用高分辨率的母离子搜索方法，我们首次证明了AFFF样品的低温热处理导致产生阴离子氟烷基物质，包括全氟庚烷磺酰胺、8:2氟端聚体磺酸、n -甲基全氟辛烷磺酰胺和以前未报道的化合物n -2-丙烯-全氟己基磺酰胺。这项研究为热过程中多氟烷基物质的命运提供了关键的见解。
In this study, we investigated thermal decomposition mechanisms of cationic, zwitterionic, and anionic polyfluoroalkyl substances, including those present in aqueous film-forming foam (AFFF) samples. We present novel evidence that polyfluoroalkyl substances gave quantitative yields of perfluoroalkyl substances of different chain lengths during thermal treatment. The results support a radical-mediated transformation mechanism involving random-chain scission and end-chain scission, leading to the formation of perfluoroalkyl carboxylic acids such as perfluorooctanoic acid (PFOA) from certain polyfluoroalkyl amides and sulfonamides. Our results also support a direct thermal decomposition mechanism (chain stripping) on the nonfluorinated moiety of polyfluoroalkyl sulfonamides, resulting in the formation of perfluorooctanesulfonic acid (PFOS) and other structurally related polyfluoroalkyl compounds. Thermal decomposition of 8:2 fluorotelomer sulfonate occurred through end-chain scission and recombination reactions, successively yielding PFOS. All of the studied polyfluoroalkyl substances began to degrade at 200–300 °C, exhibiting near-complete decomposition at ≥400 °C. Using a high-resolution parent ion search method, we demonstrated for the first time that low-temperature thermal treatments of AFFF samples led to the generation of anionic fluoroalkyl substances, including perfluoroheptanesulfonamide, 8:2 fluorotelomer sulfonic acid,N-methyl perfluorooctane sulfonamide, and a previously unreported compoundN-2-propenyl-perfluorohexylsulfonamide. This study provides key insights into the fate of polyfluoroalkyl substances in thermal processes.