Jiang Fang, Wu Mengsi, Zhu Ziyao, Jiang Chenkai, Ai Zhihui, Gong Jingming
Institute of Environmental & Applied Chemistry, College of Chemistry, Central China Normal University, Wuhan 430079, PR China.
Institute of Environmental & Applied Chemistry, College of Chemistry, Central China Normal University, Wuhan 430079, PR China.
Water Res. 2025 Sep 15;284:124049. doi: 10.1016/j.watres.2025.124049. Epub 2025 Jun 18.
The persistent nature of per- and polyfluoroalkyl substances (PFAS) poses critical challenges for conventional water treatment technologies, particularly in bromide-rich matrices where coexisting bromates (e.g., coastal industrial wastewater or landfill leachate), a carcinogenic and mutagenic disinfection by-product amplifies remediation complexity. This study unveils a self-sustaining reduction-oxidation coupling (ROC) mechanism that synergistically harness hydrated electron (e) and reactive bromine species (RBS) to achieve simultaneous PFAS defluorination and bromate detoxification under UV/sulfite treatment. Through systematic experimentation and density functional theory (DFT) calculations, we demonstrate that bromate undergoes stepwise reduction to benign bromide ions while generating radical RBS (e.g., Br and Br), which electrophilically attack intermediates of hydrogen-enriched fluorotelomer carboxylates (FTCAs) through hydrogen abstraction rather than directly targeting parent perfluorooctanoic acid (PFOA). This endogenous ROC process achieved 96 % defluorination of PFOA within 240 min at pH 10, outperforming conventional UV/sulfite treatment by 36.5 %. Notably, hydrogen-fluorine exchange strengthens adjacent C - F bonds with bond dissociation energy (BDE) up to 125 kcal mol, rendering FTCAs resistant to e but susceptible to bromine radicals, confirmed by Fukui function analysis. Meanwhile, this ROC process also works effectively in bromine-containing waters treated with UV/sulfite, highlighting its universal applicability in real-world water matrices. Across diverse water matrices (e.g., tap water or lake water), the system maintained >70 % defluorination efficiency. Additionally, this eₐ⁻/RBS-mediated ROC process demonstrated chain-length universality for C4-C8 perfluorocarboxylic acids and perfluorooctanesulfonic acid, while also detoxifying bromate to benign Br, exemplifying its effectiveness in treating PFAS-contaminated waters with elevated bromide concentrations (e.g., seawater and brine), especially regions burdened with both PFASs and bromate contamination. By exploiting inherent water components as process catalysts, this work establishes a paradigm-shifting strategy for complex PFAS remediation without exogenous oxidant addition, offering dual environmental benefits through concurrent contaminant degradation and disinfection byproduct control.
全氟和多氟烷基物质（PFAS）的持久性给传统水处理技术带来了严峻挑战，尤其是在富含溴化物的基质中，如沿海工业废水或垃圾渗滤液中，共存的溴酸盐（一种致癌和致突变的消毒副产物）会加剧修复的复杂性。本研究揭示了一种自持的还原-氧化耦合（ROC）机制，该机制协同利用水合电子（e⁻）和活性溴物种（RBS），在紫外/亚硫酸盐处理下实现PFAS的同时脱氟和溴酸盐解毒。通过系统的实验和密度泛函理论（DFT）计算，我们证明溴酸盐逐步还原为良性的溴离子，同时生成自由基RBS（如Br•和Br₂），它们通过氢原子提取亲电攻击富氢氟调聚物羧酸盐（FTCAs）的中间体，而不是直接靶向母体全氟辛酸（PFOA）。这种内源性ROC过程在pH值为10时，240分钟内实现了PFOA 96%的脱氟，比传统紫外/亚硫酸盐处理性能高出36.5%。值得注意的是，氢-氟交换增强了相邻的C-F键，键解离能（BDE）高达125 kcal mol⁻¹，使FTCAs对e⁻具有抗性，但易受溴自由基攻击，福井函数分析证实了这一点。同时，这种ROC过程在紫外/亚硫酸盐处理的含溴水中也能有效发挥作用，突出了其在实际水体基质中的普遍适用性。在不同的水体基质（如自来水或湖水）中，该系统保持了>70%的脱氟效率。此外，这种e⁻/RBS介导的ROC过程对C4-C8全氟羧酸和全氟辛烷磺酸显示出链长通用性，同时还将溴酸盐解毒为良性的Br⁻，证明了其在处理高溴化物浓度的PFAS污染水体（如海水和卤水）方面的有效性，特别是在同时受到PFAS和溴酸盐污染的地区。通过利用天然水体成分作为过程催化剂，本研究建立了一种无需添加外源氧化剂的复杂PFAS修复的范式转变策略，通过同时降解污染物和控制消毒副产物提供了双重环境效益。
