State Key Joint Laboratory of Environmental Simulation and Pollution Control, Department of Environmental Science and Engineering, Tsinghua University, Beijing 100084, PR China. wang
J Hazard Mater. 2011 Sep 15;192(3):1869-75. doi: 10.1016/j.jhazmat.2011.07.026. Epub 2011 Jul 18.
Heterogeneous photocatalytic decomposition of perfluoroocatanoic acid (PFOA) by TiO(2) under 254 nm UV light was investigated. Adding oxalic acid as a hole-scavenger significantly accelerated PFOA decomposition under nitrogen atmosphere. Fluoride ion, formic acid and six shorter-chain perfluorinated carboxylic acids (PFCAs) bearing C(2)-C(7) were identified as intermediates. When using perchloric acid (HClO(4)) as a replacement of oxalic acid to maintain the same pH of the reaction solution, PFOA did not decomposition efficiently. Compared with oxalic acid, potassium iodide (KI, another hole-scavenger) also led to a slower PFOA decomposition, while the addition of an electron acceptor (potassium persulfate, K(2)S(2)O(8)) obviously inhibited PFOA decomposition. This suggested that oxalic acid played more than one role in PFOA decomposition rather than simply providing acidity and acting as a hole-scavenger. The electron paramagnetic resonance (EPR) measurements confirmed the existence of carboxyl anion radicals (CO(2)(-)) in the photocatalytic process, which was a result of the reaction between oxalic acid and photogenerated hole. These findings indicated that PFOA decomposition was primarily induced by CO(2)(-) radicals, although photogenerated electron was also conducive to PFOA decomposition. A possible mechanism for PFOA decomposition was proposed.
研究了在 254nmUV 光下 TiO(2) 对全氟辛酸（PFOA）的非均相光催化分解。在氮气气氛下，添加草酸作为空穴清除剂可显著加速 PFOA 的分解。鉴定出氟离子、甲酸和六种含有 C(2)-C(7)的短链全氟羧酸（PFCAs）作为中间产物。当使用高氯酸（HClO(4)）代替草酸来保持反应溶液的相同 pH 值时，PFOA 不会有效分解。与草酸相比，碘化钾（KI，另一种空穴清除剂）也导致 PFOA 分解速度较慢，而添加电子受体（过硫酸钾，K(2)S(2)O(8))则明显抑制 PFOA 分解。这表明草酸在 PFOA 分解中扮演了不止一个角色，而不仅仅是提供酸度并充当空穴清除剂。电子顺磁共振（EPR）测量证实了在光催化过程中存在羧酸根阴离子自由基（CO(2)(-))，这是草酸与光生空穴之间反应的结果。这些发现表明，尽管光生电子也有利于 PFOA 的分解，但 PFOA 的分解主要是由 CO(2)(-)自由基诱导的。提出了一种 PFOA 分解的可能机制。
