Department of Chemical & Environmental Engineering, University of California, Riverside, California 92521, United States.
Department of Civil & Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
Environ Sci Technol. 2021 May 18;55(10):7052-7062. doi: 10.1021/acs.est.1c00353. Epub 2021 May 5.
The UV-sulfite reductive treatment using hydrated electrons () is a promising technology for destroying perfluorocarboxylates (PFCAs, CFCOO) in any chain length. However, the C-H bonds formed in the transformation products strengthen the residual C-F bonds and thus prevent complete defluorination. Reductive treatments of fluorotelomer carboxylates (FTCAs, CF-CHCH-COO) and sulfonates (FTSAs, CF-CHCH-SO) are also sluggish because the ethylene linker separates the fluoroalkyl chain from the end functional group. In this work, we used oxidation () with hydroxyl radicals (HO•) to convert FTCAs and FTSAs to a mixture of PFCAs. This process also cleaved 35-95% of C-F bonds depending on the fluoroalkyl chain length. We probed the stoichiometry and mechanism for the oxidative defluorination of fluorotelomers. The subsequent reduction () with UV-sulfite achieved deep defluorination of the PFCA mixture for up to 90%. The following use of HO• to oxidize the H-rich residues led to the cleavage of the remaining C-F bonds. We examined the efficacy of integrated oxidative and reductive treatment of n = 1-8 PFCAs, n = 4,6,8 perfluorosulfonates (PFSAs, CF-SO), n = 1-8 FTCAs, and n = 4,6,8 FTSAs. A majority of structures yielded near-quantitative overall defluorination (97-103%), except for n = 7,8 fluorotelomers (85-89%), n = 4 PFSA (94%), and n = 4 FTSA (93%). The results show the feasibility of complete defluorination of legacy PFAS pollutants and will advance both remediation technology design and water sample analysis.
利用水合电子（）的紫外线-亚硫酸盐还原处理是一种很有前途的技术，可用于破坏任何链长的全氟羧酸酯（PFCAs，CFCOO）。然而，在转化产物中形成的 C-H 键会增强残留的 C-F 键，从而阻止完全脱氟。氟调聚物羧酸盐（FTCAs，CF-CHCH-COO）和磺酸盐（FTSAs，CF-CHCH-SO）的还原处理也很缓慢，因为乙烯键将氟烷基链与末端官能团隔开。在这项工作中，我们使用羟基自由基（HO•）氧化将 FTCAs 和 FTSAs 转化为 PFCAs 的混合物。这一过程还根据氟烷基链的长度，裂解了 35-95%的 C-F 键。我们研究了氧化脱氟氟调聚物的化学计量和机制。随后，用紫外线-亚硫酸盐还原将 PFCAs 混合物深度脱氟，最高可达 90%。接下来，使用 HO•氧化富含氢的残留物，导致剩余的 C-F 键断裂。我们检查了集成氧化和还原处理 n = 1-8 PFCAs、n = 4、6、8 全氟磺酸酯（PFSAs，CF-SO）、n = 1-8 FTCAs 和 n = 4、6、8 FTSAs 的效果。除了 n = 7、8 氟调聚物（85-89%）、n = 4 PFSA（94%）和 n = 4 FTSA（93%）外，大多数结构的总脱氟率接近定量（97-103%）。结果表明，完全脱氟旧代 PFAS 污染物是可行的，这将推进修复技术设计和水样分析。
