title: Efficient degradation of methabenzthiazuron photoinduced by decatungstate anion in water: kinetics and mechanistic studies.
abstract: This study concerns the elimination of methabenzthiazuron (MBTU) photocatalysed by sodium decatungstate salts W10O32(4-)·(DTA) in aqueous solution under irradiation at 365 nm. Ninety percentage of MBTU (10(-4) M) is mineralised in the presence of the photocatalyst (2×10(-4) M) after 7 d under exposure and the formation of nitrate, sulphate and ammonium confirmed this phenomenon. In aerated conditions, the photodegradation rate of MBTU clearly increased in the presence of DTA by a factor of 40 when compared to direct photolysis with ΦMBTU=2.5×10(-2) and t1/2 (MBTU)=1.4 h. Oxygen appeared essential since 2 times inhibition of MBTU disappearance and the photocatalytic cycle interrupt were observed in the absence of oxygen. The degradation mechanism has been elucidated through the photoproducts identification by LC-ESI-MS analysis. Two processes were implied in the degradation: electron transfer and H atom abstraction reactions both involving W10O32(4-∗) excited state species. In the primary steps of the degradation, the aromatic ring hydroxylation was observed by electron transfer leading to OH-MBTU isomers and H atom abstraction reaction gave benzthiazuron and a supposed demethylated product. Secondary oxidations permitted the hydroxylation of both products.
authors.affiliation: Laboratoire des Techniques Innovantes pour la Préservation de l'Environnement, Université Mentouri, 25000 Constantine, Algeria.
authors.forename: A
authors.initials: A
authors.lastname: Allaoui
authors.forename: M A
authors.initials: MA
authors.lastname: Malouki
authors.forename: P
authors.initials: P
authors.lastname: Wong-Wah-Chung
mesh_terms: D000838:Anions / Q000737:chemistry; D052160:Benzothiazoles / Q000737:chemistry*; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D052918:Environmental Restoration and Remediation; D007700:Kinetics; D008782:Methylurea Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010782:Photolysis; D021241:Spectrometry, Mass, Electrospray Ionization; D017973:Tungsten Compounds / Q000737:chemistry*; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000838:Anions; D052160:Benzothiazoles; D008782:Methylurea Compounds; D017973:Tungsten Compounds; D014874:Water Pollutants, Chemical; C025399:sodium tungstate(VI); C011912:methabenzthiazuron