Decomposition of Environmentally Persistent Fluorinated Compounds Using Sulfate Radial Anions

研究了过硫酸盐在水/液CO_2双相体系中对持久性和生物蓄积性长链（C_<11>）全氟羧酸（PFCAs）的热化学分解，建立了中和长链PFCAs固定源的技术。长链PFCAs相对不溶于水，但可溶于液态CO_2；因此，在水相光反应体系中引入液态CO_2可减少PFCA胶体颗粒的干扰。采用双相体系分解PFCAs时，反应程度是无CO_2时的6.4 ~ 51倍，主要产物为f离子。此外，本文还研究了TiO_2颗粒对空气中C_4F_9C_2H_4OH的气固非均相光化学降解氟端聚体醇（FTOHs）的作用，氟端聚体醇可能是环境中全氟羧酸（PFCAs）的前体。在TiO_2上方的空气中，C_4F_9C_2H_4OH的光照射（>290 nm）依次通过C_4F_9C_2H_4OH、C_4F_9CHO、C_nF_<2n+1>COF （n = 2和/或3）和COF_2产生CO_2。空气中相对湿度的增加加速了反应中间体的分解，导致CO_2和F-的生成增加。这表明湿度是抵消室内空气中FTOHs的关键因素。此外，还研究了亚临界水中全氟辛烷磺酸（PFOS）及相关化学物质的分解。虽然这些化学物质在纯亚临界水中表现出很少的反应活性，但在反应体系中加入零价铁促进了分解形成F-离子。该方法已成功地应用于半导体制造中抗反射涂层剂中全氟辛烷磺酸的分解。

hotochemical decomposition of persistent and bioaccumulative long-chain (C_<11>) perfluorocarboxylic acids (PFCAs) with persulfate ion in an aqueous/liquid CO_2 biphasic system was examined to develop a technique to neutralize stationary sources of the long-chain PFCAs. The long-chain PFCAs are relatively insoluble in water but are soluble in liquid CO_2 ; therefore, introduction of liquid CO_2 to the aqueous photoreaction systeth reduces the interference of colloidal PFCA particles. When the biphasic system was used to decompose these PFCAs, the extent of reaction was 6.4-51 times as high as that achieved in the absence of CO_2, and F-ions were produced as a major product.In addition, degradation of C_4F_9C_2H_4OH in air over TiO_2 particles was examined in this first report of gas-solid heterogeneous photochemical degradation of fluorotelomer alcohols (FTOHs), which may be precursors of perfluorocarboxylic acids (PFCAs) in the environment. Photoirradiation (>290 nm) of C_4F_9C_2H_4OH in air flowing over TiO_2 produced CO_2, via C_4F_9C_2H_4OH, C_4F_9CHO, C_nF_<2n+1>COF (n = 2 and/or 3), and COF_2, in that order. Increased relative humidity in the air accelerated the decomposition of the reaction intermediates, which led to increased CO_2 and F- formation. This result indicates that humidity is a key factor for counteracting FTOHs in indoor air.Furthermore, decomposition of perfluorooctanesulfonate (PFOS) and related chemicals in subcritical water was investigated. Although these chemicals demonstrated little reactivity in pure subcritical water, addition of zerovalent iron to the reaction system enhanced the decomposition to form F- ions. This method was successfully applied to the decomposition of PFOS contained in an antireflective coating agent used in semiconductor manufacturing.