Effects of pH on photochemical decomposition of perfluorooctanoic acid in different atmospheres by 185nm vacuum ultraviolet.
Effects of pH on photochemical decomposition of perfluorooctanoic acid in different atmospheres by 185nm vacuum ultraviolet.
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DOI：
10.1016/j.jes.2014.09.003
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发表时间：
2014-11
影响因子：
6.9
通讯作者：
Y. Wang;Pengyi Zhang
中科院分区：
文献类型：
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作者：
Y. Wang;Pengyi Zhang
全氟辛酸（PFOA）是一种持久性有机污染物，由于其在全球范围内存在且对大多数传统处理工艺具有抗性，因此受到越来越多的关注。185 nm真空紫外光降解是降解PFOA的有效方法之一。研究了pH值对PFOA在氮气和氧气气氛下分解的影响。PFOA水溶液初始pH值为4.5时，在氮气和氧气气氛下均能有效降解。但当pH值升高到12.0时，PFOA在氧气气氛中的分解受到很大抑制，而在氮气气氛中的分解则大大加速，半衰期很短（9 min）。此外，最初包含在PFOA分子中的氟原子几乎完全转化为氟离子。提出了两种分解途径来解释不同条件下PFOA的分解。在酸性和中性溶液中，PFOA主要通过直接光解而分解;而在碱性溶液和无氧条件下，PFOA的分解主要由水合电子引起。
Perfluorooctanoic acid (PFOA), a persistent organic pollutant, receives increasing concerns due to its worldwide occurrence and resistance to most conventional treatment processes. The photochemical decomposition by 185 nm vacuum ultraviolet (VUV) is one of the efficient methods for PFOA decomposition. The effects of pH on PFOA decomposition in nitrogen atmosphere or oxygen atmosphere were investigated. At its original pH (4.5) of PFOA aqueous solution, PFOA decomposed efficiently both in nitrogen and in oxygen atmosphere. However, when the pH increased to 12.0, PFOA decomposition was greatly inhibited in oxygen atmosphere, while it was greatly accelerated in nitrogen atmosphere with a very short half-life time (9 min). Furthermore, fluorine atoms originally contained in PFOA molecules were almost completely transformed into fluoride ions. Two decomposition pathways have been proposed to explain the PFOA decomposition under different conditions. In acidic and neutral solutions, PFOA predominantly decomposesviathe direct photolysis in both atmospheres; while in the alkaline solution and in the absence of oxygen, the decomposition of PFOA is mainly induced by hydrated electrons.