title: Photocatalytic decomposition of crotamiton over aqueous TiO(2) suspensions: determination of intermediates and the reaction pathway.
abstract: The photocatalytic degradation of crotamiton in aqueous solution using TiO(2) was investigated. To investigate the effect of initial pH, the photodegradation behaviors of three types of pharmaceuticals were compared (crotamiton, clofibric acid, sulfamethoxazole). The degradation rates of crotamiton in the pH range 3-9 were nearly equal, but those of clofibric acid and sulfamethoxazole were affected by pH. At pH>6.5, TiO(2) particles, clofibric acid and sulfamethoxazole had negative charge, therefore, the repulsive force between TiO(2) particles and anionic pharmaceuticals occurred and a low reaction rate at high pH was observed. The effect of UV intensity and TiO(2) concentration on photodegradation efficiency was also investigated. Linear and logarithmical relationships between UV intensity, TiO(2) concentration and the reaction rate constant were confirmed. Furthermore, the structures of photodegradation intermediates formed concomitantly with the disappearance of crotamiton were estimated. Seven intermediates were characterized by LC/MS/MS analyses, and it was assumed that the photocatalytic degradation of crotamiton was initiated by the attack of electrophilic hydroxyl radicals on aromatic rings and alkyl chains.
authors.affiliation: Research and Education Faculty, Natural Sciences Cluster, Agriculture Unit, Kochi University, 200 Monobe Otsu, Nankoku, Kochi, Japan. jm-fukahori@kochi-u.ac.jp
authors.forename: Shuji
authors.initials: S
authors.lastname: Fukahori
authors.forename: Taku
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Ryusei
authors.initials: R
authors.lastname: Ito
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Funamizu
mesh_terms: D002384:Catalysis; D002853:Chromatography, Liquid; D002995:Clofibric Acid; D006863:Hydrogen-Ion Concentration; D010782:Photolysis; D013420:Sulfamethoxazole / Q000737:chemistry; D053719:Tandem Mass Spectrometry; D014025:Titanium / Q000737:chemistry*; D014052:Toluidines / Q000737:chemistry* / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D014052:Toluidines; C009495:titanium dioxide; D002995:Clofibric Acid; D014025:Titanium; C005553:crotamiton; D013420:Sulfamethoxazole