链长和官能团对全氟有机酸降解路径的影响

Effect of carbon chain length and functional group on decomposition pathway of perfluorinated organic acids

考察了碳链长度和官能团对高强UV/SO3^2-体系降解全氟有机酸的影响,选取典型全氟有机酸PFOA和PFOS,探明其降解机制.结果表明,高强UV/SO3^2-体系可高效降解5种全氟有机酸.全氟有机酸的降解速率随着碳链长度的增加而增加.官能团对全氟有机酸的降解有重要影响,全氟羧酸在体系中的降解速率显著快于全氟磺酸.全氟羧酸是从与羧基相连的α碳上的氟原子开始,通过逐步脱CF2单元的形式生成短链全氟羧酸进行降解.全氟磺酸主要有三条降解路径:脱磺酸基、α位脱氟以及中心C—C键断裂.

Effect of carbon chain length and functional group on decomposition of perfluorinated organic acids by the high intensity UV/sulfite system was investigated in this study. Typical perfluorinated organic acids, such as PFOA and PFOS, were selected to reveal their decomposition mechanisms. The results showed five kinds of perfluorinated organic acids were efficiently decomposed in this system, and their decomposition rate increased with increase of carbon chain length. Functional group played an important role in decomposition of perfluorinated organic acids. Decomposition rate of perfluorocarboxylic acids was obviously faster than perfluorosulfonic acids. Decomposition of perfluorocarboxylic acids started from the fluorine atom at α-position bonding with carboxyl, and then underwent decomposition with stepwise elimination of CF2 to form short chain perfluorocarboxylic acids. Desulfonation, defluorination at α position and centermost C—C bond scission were three main decomposition pathways of perfluorosulfonic acids.