Ion exchange (IX) can effectively remove per- and poly-fluoroalkyl substances (PFAS) from drinking water sources at ng/L to µg/L levels. However, adsorbed PFAS on spent resins should be further destructed for detoxification. Traditional resin incineration or landfilling may cause secondary pollution to the surrounding environment and cannot achieve resin reuse. This study explored three variations of a PFAS treatment train, aiming to completely defluorinate PFAS with different chain lengths and functional groups at environmentally relevant levels (ng/L) and to reuse the resins and solvents. The optimized treatment train includes IX, resin regeneration with 5 wt% NaCl and 60 % v/v methanol, distillation of waste regenerant, and advanced reduction by hydrated electrons (eaq−) generated during the ultraviolet/sulfite (UV/sulfite) treatment of still bottoms. Such a treatment train achieved nearly 100 % PFAS removal from surface water and groundwater using either PFAS-specific or generic resins, and almost 100 % defluorination of PFAS except a few short-chain fluorinated sulfonates and ethers. Regenerated resins had comparable PFAS removal to the pristine resins over three cycles. The generic resins (e.g., Dupont AmberLite™ IRA910) are easier to regenerate and thus are recommended for the treatment train over PFAS-selective resins (e.g., Purofine® PFA694E). Direct heterogenous defluorination on resins loaded with perfluorooctane sulfonate (PFOS) was ineffective, potentially due to the consumption of UV light/eaq− by the resins and insufficient contact between the UV light/eaq− with PFOS on the resin surface. Distillation of the waste regenerant successfully concentrated PFAS in the still bottoms, reduced the waste volume, and removed excess methanol, all essential for effective UV/sulfite treatment. Meanwhile, the produced condensate with high methanol contents and low PFAS levels can be reused for the next regeneration cycle. Findings from this study provide a timely and sustainable solution to the stringent and evolving regulations on PFAS and the resultant production of PFAS-laden resins as hazardous wastes.

中文翻译：

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利用离子交换、树脂再生和 UV/亚硫酸盐还原，循环去除和破坏水中的全氟烷基和多氟烷基物质


离子交换 （IX） 可以有效去除饮用水源中 ng/L 至 μg/L 水平的全氟和多氟烷基物质 （PFAS）。但是，应进一步分解废树脂上吸附的 PFAS 以进行解毒。传统的树脂焚烧或填埋可能会对周围环境造成二次污染，无法实现树脂再利用。本研究探讨了 PFAS 处理系列的三种变体，旨在在环境相关水平 （ng/L） 上完全脱氟具有不同链长和官能团的 PFAS，并重复使用树脂和溶剂。优化的处理方案包括 IX、使用 5 wt% NaCl 和 60 % v/v 甲醇进行树脂再生、废料再生剂的蒸馏以及在蒸馏器底部紫外线/亚硫酸盐 （UV/亚硫酸盐） 处理过程中产生的水合电子 （eaq−） 的高级还原。这种处理系统使用 PFAS 特异性树脂或通用树脂从地表水和地下水中实现了近 100% 的 PFAS 去除，并且除了少数短链氟化磺酸盐和醚外，PFAS 的脱氟率几乎达到 100%。再生树脂在三个循环中的PFAS去除率与原始树脂相当。通用树脂（例如杜邦 AmberLite™ IRA910）更容易再生，因此推荐用于 PFAS 选择性树脂（例如 Purofine® PFA694E）的处理系列。对负载全氟辛烷磺酸盐 （PFOS） 的树脂进行直接异质脱氟是无效的，这可能是由于树脂消耗了紫外线/eaq−，以及紫外线/eaq− 与树脂表面的 PFOS 接触不足。 废液再生剂的蒸馏成功地将 PFAS 浓缩在蒸馏器底部，减少了废液量，并去除了过量的甲醇，这些都是有效处理紫外线/亚硫酸盐所必需的。同时，产生的甲醇含量高、PFAS 含量低的冷凝物可以重新用于下一个再生周期。这项研究的结果为严格且不断发展的 PFAS 法规以及由此产生的含 PFAS 树脂作为危险废物提供了及时且可持续的解决方案。