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首页> 外文期刊>Environmental Science & Technology >Thermal Decomposition of Anionic, Zwitterionic, and Cationic Polyfluoroalkyl Substances in Aqueous Film-Forming Foams
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Thermal Decomposition of Anionic, Zwitterionic, and Cationic Polyfluoroalkyl Substances in Aqueous Film-Forming Foams

机译：阴离子，两性离子和阳离子聚氟烷基物质的热分解含水成膜泡沫中的泡沫

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摘要

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 compound N-2-propenyl-perfluorohexylsulfonamide. This study provides key insights into the fate of polyfluoroalkyl substances in thermal processes.
机译：在该研究中，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，包括存在于形成含水膜形成泡沫（AFFF）样品中的那些。我们提出了新的证据，即多氟烷基物质在热处理期间对不同链长度的全氟烷基物质进行定量产量。结果支持涉及随机链裂殖和终链裂变的激进介导的转化机制，从而形成来自某些多氟烷基酰胺和磺酰胺的全氟卤代酸（PFOA）的全氟烷基羧酸。我们的结果还支持在聚氟烷基磺酰胺的非氟化部分上的直接热分解机制（链剥离），导致全氟辛磺酸（PFOS）和其他结构相关的多氟烷基化合物的形成。通过终链裂变和重组反应发生8：2的氟丙二醇聚合物磺酸盐的热分解，连续产生PFO。所有研究的多氟烷基物质开始于200-300℃下降解，表现出≥400°C的接近完全分解。使用高分辨率父离子搜索方法，我们首次证明了缺粮样品的低温热处理导致了阴离子氟代烷基物质的产生，包括全氟庚酰胺，8：2氟丙二醇磺酸，N-甲基全氟辛烷磺酰胺，和先前未报告的化合物N-2-丙烯基 - 全氟己基磺酰胺。本研究为热过程中的多氟烷基物质的命运提供了关键洞察。

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