State Key Joint Laboratory of Environment Simulation and Pollution Control (SKJLESPC), Beijing Key Laboratory for Emerging Organic Contaminants Control (BKLEOC), School of Environment, POPs Research Center, Tsinghua University, Beijing 100084, China; State Key Laboratory of Water Resource Protection and Utilization in Coal Mining, China Energy Investment Corporation Limited, Beijing 102200, China.
State Key Joint Laboratory of Environment Simulation and Pollution Control (SKJLESPC), Beijing Key Laboratory for Emerging Organic Contaminants Control (BKLEOC), School of Environment, POPs Research Center, Tsinghua University, Beijing 100084, China.
J Hazard Mater. 2021 Apr 15;408:124875. doi: 10.1016/j.jhazmat.2020.124875. Epub 2020 Dec 18.
6:2 Fluorotelomer sulfonic acid (6:2 FTS) is used as alternative to perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) for different purposes such as chrome mist suppressant (CMS) and active ingredient in fire-fighting foams. In this study, degradability of 6:2 FTS under ultraviolet/persulfate (UV/PS) and ultraviolet/sulfite (UV/SF), which are typical technologies for advanced oxidation and reduction, were investigated respectively. Due to the hydrogenated moiety, 6:2 FTS was decomposed completely by UV/PS within 10 min, forming a mixture of short-chain perfluoroalkyl carboxylic acids with variable chain length (2-7 carbon atoms). Such oxidation products account for > 50% organofluorine of 6:2 FTS unmineralized portion. 6:2 FTS degradability under reductive UV/SF system was dramatically slowed down by the hydrogenated moiety, which lowered electron affinity and, consequently, reactivity with aqueous electron (e‾) produced by UV/SF. Fluorine mass balance showed that degradation intermediates were almost negligible: most of decomposed 6:2 FTS fluorine was converted to fluoride. A real 6:2 FTS-based CMS solution prepared from a commercial product was also tested. Both types of treatment were effective and in good agreement with the trends observed for tests with sole 6:2 FTS. Moreover, experimental results highlighted a remarkable amount of identifiable (like 4:2 FTS, 8:2 FTS and other per-/polyfluoroalkyl substances) and unidentifiable components in the CMS mixture. Indeed, fluoride concentration under UV/SF (73.8 mg/L) and UV/PS (44.9 mg/L) treatment were both higher than the estimated total concentration (<23 mg/L, according to 6:2 FTS concentration). Results strongly suggest that an oxidation pretreatment followed by reduction might be a better way to degrade and defluorinate 6:2 FTS and other precursors with non-fluorinated moieties, rather than employing single reduction or oxidation technology.
6:2 氟代烷烃磺酸（6:2 FTS）被用作全氟辛烷磺酸（PFOS）和全氟辛酸（PFOA）的替代品，用于不同的用途，如铬雾抑制剂（CMS）和消防泡沫中的有效成分。在这项研究中，分别研究了紫外线/过硫酸盐（UV/PS）和紫外线/亚硫酸盐（UV/SF）这两种典型的高级氧化还原技术下 6:2 FTS 的可降解性。由于氢化部分，6:2 FTS 在 10 分钟内完全被 UV/PS 分解，形成了具有可变链长（2-7 个碳原子）的短链全氟烷烃羧酸混合物。这些氧化产物占未矿化部分 6:2 FTS 有机氟的>50%。由于氢化部分降低了电子亲和力，从而降低了与 UV/SF 产生的水合电子（e‾）的反应性，6:2 FTS 在还原 UV/SF 体系下的可降解性显著减慢。氟质量平衡表明，降解中间产物几乎可以忽略不计：大部分分解的 6:2 FTS 氟转化为氟化物。还测试了从商业产品制备的真实的 6:2 FTS 基 CMS 溶液。两种处理方法都有效，与单独使用 6:2 FTS 进行的测试所观察到的趋势非常吻合。此外，实验结果突出表明在 CMS 混合物中存在大量可识别的（如 4:2 FTS、8:2 FTS 和其他全氟/多氟烷基物质）和不可识别的成分。事实上，在 UV/SF（73.8mg/L）和 UV/PS（44.9mg/L）处理下的氟化物浓度均高于估计的总浓度（<23mg/L，根据 6:2 FTS 浓度）。结果强烈表明，与单一还原或氧化技术相比，氧化预处理后还原可能是降解和脱氟 6:2 FTS 和其他具有非氟化部分的前体的更好方法。
