title: Light-induced degradation of perfluorocarboxylic acids in the presence of titanium dioxide.
abstract: The UV-photon-induced degradation of heptafluorobutanoic acid was investigated in acidic aqueous solutions in the presence of titanium dioxide. Heptafluorobutanoic acid could be degraded with this photocatalyst in a light-induced reaction generating carbon dioxide and fluoride anions. Carbon dioxide evolution in a significant amount occurred only in the presence of molecular oxygen and the photocatalyst. The light-induced degradation of trifluoroacetic acid, pentafluoropropanoic acid, nonafluorobutanoic acid, pentadecafluorooctanoic acid, nonafluorobutanesulfonic acid, and heptadecafluorooctanesulfonic acid in the presence of titanium dioxide was also studied. The perfluorocarboxylic acids under investigation are degraded to generate CO(2) and fluoride anions while both perfluorinated sulfonic acids are persistent under the experimental conditions employed in this study. For all compounds photonic efficiencies of the mineralization reaction were estimated to be smaller than 1x10(-5). To increase the photocatalytic activity mixed systems containing homogeneous phosphotungstic acid and heterogeneous titanium dioxide catalysts were also investigated. In the mixtures of these two photocatalysts, the formation rate of CO(2) increased with illumination time.
authors.affiliation: Frontier Research Center for the Global Environment Science, Meisei University, 2-1-1 Hodokubo, Hino-shi, Tokyo 191-8506, Japan.
authors.forename: Ralf
authors.initials: R
authors.lastname: Dillert
authors.forename: Detlef
authors.initials: D
authors.lastname: Bahnemann
authors.forename: Hisao
authors.initials: H
authors.lastname: Hidaka
mesh_terms: D017738:Alkanesulfonic Acids / Q000737:chemistry / Q000528:radiation effects; D002210:Caprylates / Q000737:chemistry / Q000528:radiation effects; D002384:Catalysis; D004785:Environmental Pollutants / Q000737:chemistry / Q000528:radiation effects; D052918:Environmental Restoration and Remediation / Q000379:methods; D005466:Fluorocarbons / Q000737:chemistry / Q000528:radiation effects*; D010772:Phosphotungstic Acid / Q000737:chemistry; D010782:Photolysis; D014025:Titanium / Q000737:chemistry*; D014269:Trifluoroacetic Acid / Q000737:chemistry / Q000528:radiation effects; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000528:radiation effects
chemical_list: D017738:Alkanesulfonic Acids; D002210:Caprylates; D004785:Environmental Pollutants; D005466:Fluorocarbons; D014874:Water Pollutants, Chemical; D010772:Phosphotungstic Acid; C009495:titanium dioxide; C033094:perfluorobutyric acid; C033093:perfluoropropionic acid; C023036:perfluorooctanoic acid; C076994:perfluorooctane sulfonic acid; D014025:Titanium; D014269:Trifluoroacetic Acid