School of Environmental and Municipal Engineering, Qingdao Technological University, Qingdao 266033, China.
J Environ Sci (China). 2012;24(4):774-80. doi: 10.1016/s1001-0742(11)60818-8.
Perfluorooctanoic acid (PFOA) is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical (HO*) due to its stable chemical structure and the high electronegativity of fluorine. Photocatalytic reduction of PFOA with beta-Ga2O3 in anoxic aqueous solution was investigated for the first time, and the results showed that the photoinduced electron (e(cb-)) coming from the beta-Ga2O3 conduction band was the major degradation substance for PFOA, and shorter-chain perfluorinated carboxylic acids (PFCAs, CnF2n+i1COOH, 1 < or = n < or = 6) were the dominant products. Furthermore, the concentration of F- was measured by the IC technique and defluorination efficiency was calculated. After 3 hr, the photocatalytic degradation efficiency was 98.8% and defluorination efficiency was 31.6% in the presence of thiosulfate and bubbling N2. The degradation reaction followed first-order kinetics (k = 0.0239 min(-1), t1/2 = 0.48 hr). PFCAs (CnF2n+1COOH, 1 < or = n < or = 7) were detected and measured by LC-MS and LC-MS/MS methods. It was deduced that the probable photocatalytic degradation mechanism involves e(cb-) attacking the carboxyl of CnF2n+1COOH, resulting in decarboxylation and the generation of CnF2n+1*. The produced CnF2n+1* reacted with H2O, forming CnF2n+1OH, then CnF2n+1OH underwent HF loss and hydrolysis to form CnF2n+1COOH.
全氟辛酸（PFOA）是一种新发现的有害持久性有机污染物，由于其稳定的化学结构和氟的高电负性，它不易被羟基自由基（HO*）分解。首次研究了β-Ga2O3在缺氧水溶液中光催化还原 PFOA 的情况，结果表明，来自β-Ga2O3导带的光致电子（e(cb-))是 PFOA 的主要降解物质，短链全氟羧酸（PFCAs，CnF2n+i1COOH，1 < or = n < or = 6)是主要产物。此外，通过 IC 技术测量 F-的浓度并计算脱氟效率。在存在硫代硫酸盐和鼓泡 N2 的情况下，3 小时后，光催化降解效率为 98.8%，脱氟效率为 31.6%。降解反应遵循一级动力学（k = 0.0239 min(-1), t1/2 = 0.48 小时）。通过 LC-MS 和 LC-MS/MS 方法检测并测量了 PFCAs（CnF2n+1COOH，1 < or = n < or = 7）。推断出可能的光催化降解机制涉及 e(cb-)攻击 CnF2n+1COOH 的羧基，导致脱羧和生成 CnF2n+1*。生成的 CnF2n+1*与 H2O 反应，形成 CnF2n+1OH，然后 CnF2n+1OH 经历 HF 损失和水解形成 CnF2n+1COOH。
