State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
J Environ Sci (China). 2020 Nov;97:132-140. doi: 10.1016/j.jes.2020.05.006. Epub 2020 Jun 9.
As a novel alternative to traditional perfluoroalkyl substances (PFASs), including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), hexafluoroproplyene oxide trimer acid (HFPO-TA) has been detected worldwide in surface water. Moreover, recent researches have demonstrated that HFPO-TA has stronger bioaccumulation potential and higher hepatotoxicity than PFOA. To treat these contaminants e.g. PFOA and PFOS, some photochemical techniques by adding exogenous substances had been reported. However, there is still no report for the behavior of HFPO-TA itself under direct UV irradiation. The current study investigated the photo-transformation of HFPO-TA under UV irradiation in aqueous solution. After 72 hr photoreaction, 75% degradation ratio and 25% defluorination ratio were achieved under ambient condition. Reducing active species, i.e., hydrated electrons and active hydrogen atoms, generated from water splitting played dominant roles in degradation of HFPO-TA, which was confirmed by different effects of reaction atmospheres and quenching experiments. A possible degradation pathway was proposed based on the products identification and theoretical calculations. In general, HFPO-TA would be transformed into shorter-chain PFASs, including hexafluoropropylene oxide dimer acid (HFPO-DA), perfluoropropionic acid (PFA) and trifluoroacetate (TFA). This research provides basic information for HFPO-TA photodegradation process and is essential to develop novel remediation techniques for HFPO-TA and other alternatives with similar structures.
作为传统全氟烷基物质（PFASs）的替代物，包括全氟辛酸（PFOA）和全氟辛烷磺酸（PFOS），六氟丙烯氧化物三聚体酸（HFPO-TA）已在世界范围内的地表水和废水中被检测到。此外，最近的研究表明，HFPO-TA 具有比 PFOA 更强的生物蓄积潜力和更高的肝毒性。为了处理这些污染物，例如 PFOA 和 PFOS，已经报道了一些通过添加外源物质的光化学技术。然而，目前还没有关于 HFPO-TA 本身在直接紫外辐射下的行为的报道。本研究考察了 HFPO-TA 在水溶液中紫外光照射下的光转化行为。在 72 小时的光反应后，在环境条件下，降解率达到 75%，脱氟率达到 25%。水分解产生的具有还原活性的物质，即水合电子和活性氢原子，在 HFPO-TA 的降解中起主要作用，这通过不同的反应气氛和猝灭实验得到了证实。基于产物的鉴定和理论计算，提出了可能的降解途径。一般来说，HFPO-TA 会转化为较短链的 PFASs，包括六氟丙烯氧化物二聚酸（HFPO-DA）、全氟丙酸（PFA）和三氟乙酸（TFA）。这项研究为 HFPO-TA 的光降解过程提供了基础信息，对于开发 HFPO-TA 和其他具有类似结构的替代品的新型修复技术至关重要。
