Electrochemical Oxidation of Hexafluoropropylene Oxide Dimer Acid (GenX): Mechanistic Insights and Efficient Treatment Train with Nanofiltration,Environmental Science & Technology

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Electrochemical Oxidation of Hexafluoropropylene Oxide Dimer Acid (GenX): Mechanistic Insights and Efficient Treatment Train with Nanofiltration
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2019-10-24 , DOI: 10.1021/acs.est.9b03171
Nasim E. Pica ₁ , Joanna Funkhouser ₁ , Yiming Yin ₁ , Zuoyou Zhang ₁ , Donato M. Ceres ₂ , Tiezheng Tong ₁ , Jens Blotevogel ₁

Affiliation

Hexafluoropropylene oxide dimer acid (HFPO-DA, trade name GenX) is a perfluoroalkyl ether carboxylic acid (PFECA) that has been detected in watersheds around the world. Similar to other per- and polyfluoroalkyl substances (PFASs), few processes are able to break HFPO-DA’s persistent carbon–fluorine bonds. This study provides both experimental and computational lines of evidence for HFPO-DA mineralization during electrochemical oxidation at a boron-doped diamond anode with a low potential for the generation of stable organofluorine intermediates. Our density functional theory calculations consider the major operative mechanism, direct electron transfer, throughout the entire pathway. Initial oxidative attack does not break the ether bond, but leads to stepwise mineralization of the acidic side chain. Our mechanistic investigations reveal that hydroxyl radicals are unreactive toward HFPO-DA, while electrochemically activated sulfate facilitates its oxidation. Furthermore, we demonstrate that an NF90 membrane is capable of removing 99.5% of HFPO-DA from contaminated water. Electrochemical treatment of the nanofiltration rejectate is shown to reduce both energy and electrode costs by more than 1 order of magnitude compared to direct electrochemical treatment of the raw water. Overall, a nanofiltration–electrochemical oxidation treatment train is a sustainable destructive approach for the cost-effective elimination of HFPO-DA and other PFASs from contaminated water.

中文翻译：

六氟环氧丙烷二聚酸（GenX）的电化学氧化：纳米过滤的机理见解和高效处理方法

六氟环氧丙烷二聚酸（HFPO-DA，商品名GenX）是一种全氟烷基醚羧酸（PFECA），已在世界各地的流域中被发现。与其他全氟烷基物质和多氟烷基物质（PFAS）相似，很少有方法能够破坏HFPO-DA的持久性碳氟键。这项研究提供了在掺硼金刚石阳极上进行电化学氧化过程中HFPO-DA矿化的实验和计算证据，这对于稳定有机氟中间体的生成具有较低的潜力。我们的密度泛函理论计算考虑了整个路径中的主要作用机理，即直接电子转移。最初的氧化攻击不会破坏醚键，但会导致酸性侧链的逐步矿化。我们的机理研究表明，羟基自由基对HFPO-DA无反应，而电化学活化的硫酸盐则有助于其氧化。此外，我们证明了NF90膜能够从污水中去除99.5％的HFPO-DA。与直接对原水进行电化学处理相比，对纳滤滤出物进行电化学处理可将能量和电极成本降低超过1个数量级。总体而言，纳滤-电化学氧化处理技术是一种可持续的破坏性方法，可以经济高效地从污染水中消除HFPO-DA和其他PFAS。我们证明了NF90膜能够从污水中去除99.5％的HFPO-DA。与直接对原水进行电化学处理相比，对纳滤滤出物进行电化学处理可将能源和电极成本降低超过1个数量级。总体而言，纳滤-电化学氧化处理技术是一种可持续的破坏性方法，可以经济高效地从污染水中消除HFPO-DA和其他PFAS。我们证明了NF90膜能够从污水中去除99.5％的HFPO-DA。与直接对原水进行电化学处理相比，对纳滤滤出物进行电化学处理可将能源和电极成本降低超过1个数量级。总体而言，纳滤-电化学氧化处理技术是一种可持续的破坏性方法，可以经济高效地从污染水中消除HFPO-DA和其他PFAS。

更新日期：2019-10-24

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