Emerging investigator series: electrochemically-mediated remediation of GenX using redox-copolymers
Emerging investigator series: electrochemically-mediated remediation of GenX using redox-copolymers
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DOI：
10.1039/d1ew00544h
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发表时间：
2021-09-30
影响因子：
5
通讯作者：
Su, Xiao
中科院分区：
文献类型：
--
作者：
Baldaguez Medina, Paola;Cotty, Stephen;Su, Xiao
全氟烷基物质和多氟烷基物质 (PFAS) 是持久性污染物，在全球地下水和饮用水中不断检测到。六氟环氧丙烷二聚酸（商品名 GenX）已被用来替代传统的 PFAS，例如 PFOA，但其大量使用导致水流中广泛存在，且含量往往很高。在这里，我们评估了氧化还原共聚物聚(4-甲基丙烯酰氧基-2,2,6,6-四甲基哌啶-1-氧基-co-4-甲基丙烯酰氧基-2,2,6,6-四甲基哌啶)(PTMA-co-PTMPMA)对GenX的选择性电化学去除。胺官能团促进对阴离子 PFAS 的亲和力，氧化还原活性硝基氧自由基为吸附和解吸提供电化学控制。与开路相比，当施加 0.8 V vs. Ag/AgCl 电势时，氧化还原共聚物可以获得更快的动力学和更高的吸收（>475 mg g(-1) 吸附剂）。共聚物电吸附剂在较宽的 pH 范围和不同的水基质中进行了评估，其静电机制取决于 PFAS 的质子化状态。此外，我们将氧化还原电极从批量配置转换为流通池配置，显示在流量和电化学控制下成功吸附和释放 GenX。最后，GenX 长时间暴露在还原电位下，会在氧化还原电极处产生更小的 PFAS 碎片。为了完全脱氟 GenX，将共聚物功能化电极与掺硼金刚石 (BDD) 对电极耦合，将分离和脱氟集成在同一装置内。该组合系统的脱氟效率接近 100%。因此，我们强调了电活性氧化还原平台在含氟调聚物反应分离方面的潜力，并指出了其在水处理中的实际应用的未来方向。
Per- and polyfluorinated alkyl substances (PFAS) are persistent contaminants that have been continuously detected in groundwater and drinking water around the globe. Hexafluoropropylene oxide dimer acid (tradename GenX) has been used to substitute traditional PFAS, such as PFOA, but its intense use has caused widespread occurrence in water streams and often in high levels. Here, we evaluate a redox-copolymer, poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidin-1-oxyl-co-4-methacryloyloxy-2,2,6,6-tetramethylpiperidine) (PTMA-co-PTMPMA), for the selective electrochemical removal of GenX. The amine functional groups promote affinity towards the anionic PFAS, and the redox-active nitroxide radicals provide electrochemical control for adsorption and desorption. Faster kinetics and higher uptake (>475 mg g(-1) adsorbent) were obtained with the redox-copolymer when applying 0.8 V vs. Ag/AgCl potential compared to open circuit. The copolymer electrosorbents were evaluated over a wide pH range and diverse water matrices, with electrostatic-based mechanisms dependent on the state of protonation of the PFAS. Moreover, we translated the redox-electrodes from a batch to flow-by cell configuration, showing successful adsorption and release of GenX under flow and electrochemical control. Finally, prolonged exposure of GenX at reduction potentials generated smaller PFAS fragments at the redox-electrodes. To fully defluorinate GenX, the copolymer-functionalized electrodes were coupled with a boron-doped diamond (BDD) counter electrode for integrating separation and defluorination within the same device. The combined system demonstrated close to 100% defluorination efficiency. Thus, we highlight the potential of electroactive redox platforms for the reactive separation of fluorotelomers, and point to future directions for their practical implementation for water treatment.