Decomposition of Environmentally Persistent Fluorinated Compounds Using Sulfate Radial Anions

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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.