Xiamen Engineering & Technology Research Center for Urban Water Environment Planning and Remediation, College of Civil Engineering, Huaqiao University, Xiamen, 361021, China.
Analytical and Testing Center of Huaqiao University, Xiamen, 361021, China.
Chemosphere. 2020 Nov;259:127502. doi: 10.1016/j.chemosphere.2020.127502. Epub 2020 Jul 2.
The reductive degradability and decomposition pathways of linear perfluorooctanesulfonate (L-PFOS) were investigated in a biomimetic system consisting of Ti(III)-citrate and Vitamin B. Biomimetic degradation of L-PFOS could well be described by a first-order exponential decay model. Accompanied by the release of fluoride ion, technical PFOS could not only be transformed to perfluorocarboxylates (PFCAs) and perfluoroalkylsulfonates (PFSAs) with perfluoroalkyl carbon chain length < C8 (thereafter referred as carbon-chain-shortened degradation products), but also be transformed to PFCAs with perfluoroalkyl carbon chain length ≥ C8 (thereafter referred as carbon-chain-lengthened degradation products). Perfluorohexanesulfonate and perfluorotetradecanoate were the most abundant carbon-chain-shortened and -lengthened degradation products of technical PFOS, respectively. Based on the various degradation products detected during biomimetic reduction of linear [1,2,3,4-C]-PFOS, the degradation pathways of L-PFOS were proposed as follows: L-PFOS was first reduced to CF• radical by cleavage of C-S bond, and then transformed to PFOA through hydrolysis. However, the carbon-chain-shortened products were not generated through the sequential chain-shortening via CF• radicals and/or L-PFOS, while the carbon-chain-lengthened products were not formed via CF• radicals by stepwise addition of CF moiety. In fact, CF• radical and/or L-PFOS were further reduced to form CF• (n = 1, 2, 3, 4) radicals, and these radicals were chain-lengthened by stepwise addition of CF moiety and eventually transformed to various degradation products via hydrolysis (PFCAs) or combination reaction with sulfonyl hydroxide (PFSAs). All carbon-chain-lengthened chemicals were first reported as the degradation products during the decomposition of L-PFOS, while carbon-chain-shortened compounds were first identified as the biomimetic reduction products of L-PFOS.
研究了由 Ti(III)-柠檬酸盐和维生素 B 组成的仿生体系中线性全氟辛烷磺酸 (L-PFOS) 的还原降解途径。L-PFOS 的仿生降解可以很好地用一级指数衰减模型来描述。在释放氟离子的同时，技术 PFOS 不仅可以转化为具有< C8 个全氟烷基碳链长度的全氟羧酸 (PFCAs) 和全氟烷基亚磺酸盐 (PFSAs)（以下简称碳链缩短降解产物），还可以转化为具有≥ C8 个全氟烷基碳链长度的 PFCAs（以下简称碳链延长降解产物）。全氟己烷磺酸盐和全氟十四烷酸酯分别是技术 PFOS 的最丰富的碳链缩短和延长降解产物。基于线性 [1,2,3,4-C]-PFOS 仿生还原过程中检测到的各种降解产物，提出了 L-PFOS 的降解途径如下：L-PFOS 首先通过 C-S 键的断裂被还原为 CF•自由基，然后通过水解转化为 PFOA。然而，碳链缩短产物不是通过 CF•自由基和/或 L-PFOS 的连续链缩短生成的，而碳链延长产物不是通过 CF•自由基通过 CF 部分的逐步加成生成的。事实上，CF•自由基和/或 L-PFOS 进一步还原形成 CF•（n = 1、2、3、4）自由基，这些自由基通过 CF 部分的逐步加成链延长，最终通过水解（PFCAs）或与磺酰基氢氧化物的结合反应（PFSAs）转化为各种降解产物。所有碳链延长的化学品都是首次作为 L-PFOS 分解过程中的降解产物报道的，而碳链缩短化合物是首次被鉴定为 L-PFOS 的仿生还原产物。
