Visible light-induced decomposition of a fluorotelomer unsaturated carboxylic acid in water with a combination of tungsten trioxide and persulfate

• C3F7CFCHCOOH was not decomposed by visible light and either TiO2 or WO3 under O2.
• Irradiation in the presence of WO3 and K2S2O8 clearly decomposed C3F7CFCHCOOH.
• The photochemical decomposition of C3F7CFCHCOOH was greater under argon than under O2.
• Under O2, formed H2O2 may have interfered with the photochemical decomposition.

Photochemical decomposition of a fluorotelomer unsaturated carboxylic acid, C3F7CFCHCOOH (1), in the presence of WO3 and an electron acceptor (S2O82- or H2O2) in water under visible-light irradiation was investigated. Under an O2 atmosphere, 1 was not decomposed either by TiO2 (P25) or WO3 alone. A combination of WO3 and H2O2 also resulted in almost no decomposition of 1. In contrast, irradiation in the presence of a combination of WO3 and S2O82- (potassium salt) efficiently decomposed 1 to F−, CO2, C3F7COOH, and C2F5COOH. The decomposition of 1 was affected by the counter cation of S2O82-: the decomposition extent was higher with K2S2O8 than with (NH4)2S2O8. The decomposition of 1 was further enhanced when the reaction in the presence of WO3 and K2S2O8 was carried out under an argon atmosphere. Under O2, the amount of H2O2 formed in the reaction solution was an order of magnitude higher than the amount formed under argon. This fact suggests that the decrease in the decomposition of 1 under O2 can be ascribed to the formation of H2O2, which consumed S2O82- and SO4-.

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