State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, PR China.
Water Res. 2010 May;44(9):2939-47. doi: 10.1016/j.watres.2010.02.019. Epub 2010 Feb 26.
Globally distributed and highly stable, perfluorooctanoic acid (PFOA) has prompted much concern regarding its accumulation in the natural environment and its threats to ecosystems. Therefore, it is desirable to develop an effective treatment against PFOA pollution. In this study, a photo-reduction method is developed and evaluated for the decomposition of perfluorooctanoic acid (PFOA) in aqueous phase with potassium iodide (KI) as a mediator. The experiment was conducted under 254 nm irradiation at room temperature and pH 9 under anaerobic conditions. Ultraviolet photolysis of iodide solutions led to the generation of hydrated electrons (e(aq)(-), E(aq/e) degrees = -2.9 V), which contributed to the defluorination of PFOA. Defluorination was confirmed by fluoride release of 98%, indicating almost complete defluorination of PFOA. Kinetic analysis indicated that the PFOA decomposition fit the first-order model with a rate constant of 7.3 x 10(-3) min(-1). Besides fluoride ions, additional intermediates identified and quantified include formic acid, acetic acid, and six short-chain perfluorocarboxylic acids (C1-C6). Furthermore, small amounts of CF(3)H and C(2)F(6) were also detected as reaction products by using GC/MS. With observation of the degradation products and verification via an isotopic labeling method, two major defluorination pathways of PFOA are proposed: direct cleavage of C-F bonds attacked by hydrated electrons as the nucleophile; and stepwise removal of CF(2) by UV irradiation and hydrolysis. This method was applied to the decomposition of PFOA in wastewater issued from a fluorochemical plant and proved to be effective.
全氟辛酸（PFOA）在全球范围内广泛分布且极为稳定，其在自然环境中的积累及其对生态系统的威胁引起了广泛关注。因此，开发一种有效处理 PFOA 污染的方法是很有必要的。本研究提出了一种光还原法，利用碘化钾（KI）作为媒介剂，在水相中分解全氟辛酸（PFOA）。实验在室温下、pH 值为 9 且无氧条件下，通过 254nm 照射进行。碘化物溶液的紫外光解会生成水合电子（e(aq)(-)，E(aq/e)°=-2.9V），这有助于 PFOA 的脱氟。通过释放 98%的氟化物来证实脱氟，表明 PFOA 几乎完全脱氟。动力学分析表明，PFOA 的分解符合一级模型，速率常数为 7.3×10(-3)min(-1)。除了氟离子，还鉴定和定量了其他中间体，包括甲酸、乙酸和六种短链全氟羧酸（C1-C6）。此外，还通过 GC/MS 检测到少量 CF(3)H 和 C(2)F(6)作为反应产物。通过观察降解产物并通过同位素标记法进行验证，提出了 PFOA 的两种主要脱氟途径：水合电子作为亲核试剂直接攻击 C-F 键的断裂；以及通过 UV 照射和水解逐步去除 CF(2)。该方法应用于氟化工厂废水的 PFOA 分解，证明是有效的。
