Persulfate-induced photochemical decomposition of a fluorotelomer unsaturated carboxylic acid in water

The persulfate (S2O82−)-induced photochemical decomposition of C3F7CF=CHCOOH in water was investigated to develop a method to neutralize stationary sources of fluorotelomer unsaturated carboxylic acids (FTUCAs), which have recently been detected in the environment, and are considered to be more toxic than the environmentally persistent perfluorocarboxylic acids (PFCAs). Photolysis of S2O82− produced highly oxidative sulfate radical anions (SO4 −), which efficiently decomposed C3F7CF=CHCOOH to F− and CO2 via C3F7COOH. With an initial S2O82− concentration of 12.5 mM and irradiation from a 200-W xenon–mercury lamp, C3F7CF=CHCOOH at a concentration of 680 μM was completely decomposed within 5 min. When 8.00 mM S2O82− was used, the initial rate of C3F7CF=CHCOOH decomposition induced by 254-nm light irradiation was 45 times as high as that with photolysis alone. The apparent quantum yield for the C3F7CF=CHCOOH decomposition with 6.25 mM S2O82− and 254-nm light was 2.4, indicating that virtually all SO4 − anions produced by the photolysis of S2O82− contribute to the decomposition of C3F7CF=CHCOOH.