title: Photocatalytic transformation of sixteen substituted phenylurea herbicides in aqueous semiconductor suspensions: intermediates and degradation pathways.
abstract: The photocatalytic degradation of sixteen substituted phenylurea herbicides (PUHs) in pure water has been studied using zinc oxide (ZnO) and titanium dioxide (TiO(2)) as photocatalyst under artificial light irradiation. Photocatalytic experiments showed that the addition of these chalcogenide oxides in tandem with the oxidant (Na(2)S(2)O(8)) strongly enhances the degradation rate of these compounds in comparison with those carried out with ZnO and TiO(2) alone and photolytic tests. Comparison of catalysts showed that ZnO is the most efficient for the removal of such herbicides in optimal conditions and at constant volumetric rate of photon absorption in the photoreactor. Thus, the complete disappearance of all the studied compounds was achieved after 20 min of illumination in the ZnO/Na(2)S(2)O(8) system. The main photocatalytic intermediates detected during the degradation of PUHs were identified. The probable photodegradation pathways were proposed and discussed. The main steps involved: N-demethylation of the N,N-dimethylurea-substituted compounds followed of N-demethylation and N-demethoxylation of the N-methoxy-N-methyl-substituted ureas and hydroxylation of aromatic rings and their aliphatic side-chains of both, parent compounds and intermediates.
authors.affiliation: Departamento de Calidad y Garantía Alimentaria, Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario (IMIDA), C/Mayor s/n, La Alberca, 30150 Murcia, Spain. jose.fenoll@carm.es
authors.forename: José
authors.initials: J
authors.lastname: Fenoll
authors.forename: Paula
authors.initials: P
authors.lastname: Sabater
authors.forename: Gines
authors.initials: G
authors.lastname: Navarro
authors.forename: Gabriel
authors.initials: G
authors.lastname: Pérez-Lucas
authors.forename: Simón
authors.initials: S
authors.lastname: Navarro
mesh_terms: D002384:Catalysis; D006540:Herbicides / Q000737:chemistry* / Q000528:radiation effects; D008027:Light; D016877:Oxidants / Q000737:chemistry; D010671:Phenylurea Compounds / Q000737:chemistry* / Q000528:radiation effects; D010782:Photolysis; D012666:Semiconductors; D017670:Sodium Compounds / Q000737:chemistry; D013431:Sulfates / Q000737:chemistry; D013535:Suspensions; D014025:Titanium / Q000737:chemistry* / Q000528:radiation effects; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000528:radiation effects; D015034:Zinc Oxide / Q000737:chemistry* / Q000528:radiation effects
chemical_list: D006540:Herbicides; D016877:Oxidants; D010671:Phenylurea Compounds; D017670:Sodium Compounds; D013431:Sulfates; D013535:Suspensions; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium; C024625:sodium persulfate; D015034:Zinc Oxide