新型 PFECA (C7 HFPO-TA) 在真空紫外/亚硫酸盐中的深度脱氟和矿化：H/OCF3 交换的独特机制,Environmental Science & Technology

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新型 PFECA (C7 HFPO-TA) 在真空紫外/亚硫酸盐中的深度脱氟和矿化：H/OCF3 交换的独特机制
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2023-09-25 , DOI: 10.1021/acs.est.3c03308
Mengbin Gu ₁ , Liquan Liu ₁ , Gang Yu ₁ , Jun Huang ₁

Affiliation

C7 HFPO-TA是一种新发现的PFOA替代品，具有独特的结构片段（CF ₃ O–CF(CF ₃ )−）。在本研究中，我们首次评估了C7 HFPO-TA在高级氧化和还原过程中的化学反应活性，揭示了一系列意想不到的转化机制。结果表明，基于水合电子（e _aq^–）的还原降解对于C7 HFPO-TA的降解更为可行。对于氧化降解，α位碳上的支链-CF ₃形成空间位阻，屏蔽SO ₄^•–对-COO ^-的攻击。^{HO •} /e _aq^–和直接光解的协同效应导致真空紫外/亚硫酸盐 (VUV/SF) 工艺中 C7 HFPO-TA 更深的脱氟和矿化。我们发现了一种独特的H/OCF ₃交换，可将CF ₃ O–CF(CF ₃ )-直接转化为H–CF(CF ₃ )-，并首次发现SO ₃^•–涉及C7 HFPO-TA的机制。我们发现，与CF ₃ O-基团相邻的相同碳连接的支链-CF ₃影响C-O键裂解位点，更倾向于H/OCF ₃交换途径。在 VUV/SF 工艺中将 C7 HFPO-TA 的脱氟与 PFOA 和三种 PFECA 进行了比较，其脱氟高度依赖于结构。降解动力学、理论计算和产物分析为C7 HFPO-TA的降解机制和途径提供了深入的视角。

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Deeper Defluorination and Mineralization of a Novel PFECA (C7 HFPO-TA) in Vacuum UV/Sulfite: Unique Mechanism of H/OCF3 Exchange

C7 HFPO-TA is a newly identified alternative to PFOA, which possesses a unique structure fragment (CF₃O–CF(CF₃)−). In this study, we evaluated the chemical reactivity of C7 HFPO-TA in advanced oxidation and reduction processes for the first time, which revealed a series of unexpected transformation mechanisms. The results showed that reductive degradation based on hydrated electrons (e_aq^–) was more feasible for the degradation of C7 HFPO-TA. For oxidative degradation, the branched −CF₃ at the α-position carbon posed as the spatial hindrance, shielding the attack of SO₄^•– to −COO^–. The synergistic effects of HO^•/e_aq^– and direct photolysis led to deeper defluorination and mineralization of C7 HFPO-TA in the vacuum UV/sulfite (VUV/SF) process. We identified a unique H/OCF₃ exchange that converted the CF₃O–CF(CF₃)- into H–CF(CF₃)- directly, and the SO₃^•– involved mechanism of C7 HFPO-TA for the first time. We revealed the branched −CF₃ connected to the same carbon next to the CF₃O- group affected the C–O bond cleavage site, preferring the H/OCF₃ exchange pathway. The defluorination of C7 HFPO-TA was compared with PFOA and three PFECAs in the VUV/SF process, which was highly dependent on structures. Degradation kinetics, theoretical calculations, and products’ analysis provided an in-depth perspective on the degradation mechanisms and pathways of C7 HFPO-TA.

更新日期：2023-09-25

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