TiO2-induced heterogeneous photodegradation of a fluorotelomer alcohol in air

Degradation of C(4)F(9)C(2)H(4)OH 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(4)F(9)C(2)H(4)OH in air flowing over TiO(2) produced CO(2), via C(4)F(9)CH(2)CHO, C(4)F(9)CHO, C(n)F(2n+1)COF (n = 2 and/or 3), and COF(2), in that order. X-ray photoelectron spectroscopy of the TiO(2) surface showed a decrease in the amount of fluorine bonded to carbon and an increase in the amount of F(-) as the degradation of C(4)F(9)C(2)H(4)OH in air proceeded. Of the carbon content in the initial C(4)F(9)C(2)H(4)OH (78.8 ppmv), 90.7% was transformed to CO(2), and the predominant fluorine species produced on the TiO(2) surface was F(-). Fluorotelomer unsaturated acids, which are considered to be toxic and have been observed in the biodegradation of FTOHs, did not form. 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. Although perfluoroalkyl substances such as PFCAs in water reportedly undergo little photodegradation over TiO(2), our data show that mineralization of C(4)F(9)C(2)H(4)OH in air can be achieved with TiO(2).