title: Photocatalytic degradation of substituted phenylurea herbicides in aqueous semiconductor suspensions exposed to solar energy.
abstract: The photocatalyzed degradation of the biocides chlorotoluron, diuron, fluometuron, isoproturon and linuron (substituted phenylurea herbicides) was investigated in aqueous suspensions of ZnO, TiO2, WO3, SnO2 and ZnS at pilot plant scale under natural sunlight. Comparison of the five catalysts showed that ZnO is the most effective for catalyzing the removal of all the compounds studied. The primary degradation of the herbicides followed a pseudo-first order kinetics. In our conditions, the time required for 90% degradation ranged from 23 to 47min for isoproturon and linuron, respectively, when using the tandem ZnO/Na2S2O8. Eight transformation products were identified by HPLC-MS(2) during the experiments, although at the end of the photoperiod (240min), their concentrations were below detection limits. Based on derivative identification, the proposed metabolic pathways would involve N-demethylation and N-demethoxylation of the N-methoxy-N-methyl substituted ureas and N-demethylation of the N,N-dimethylurea-substituted compounds.
authors.affiliation: Departamento de Calidad y Garantía Alimentaria, Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario (IMIDA), C/Mayor s/n, La Alberca, Murcia, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Fenoll
authors.forename: Marina
authors.initials: M
authors.lastname: Martínez-Menchón
authors.forename: Ginés
authors.initials: G
authors.lastname: Navarro
authors.forename: Nuria
authors.initials: N
authors.lastname: Vela
authors.forename: Simón
authors.initials: S
authors.lastname: Navarro
mesh_terms: D006540:Herbicides / Q000032:analysis / Q000737:chemistry*; D008956:Models, Chemical; D010671:Phenylurea Compounds / Q000032:analysis / Q000737:chemistry*; D010782:Photolysis; D012666:Semiconductors; D013472:Sunlight; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D006540:Herbicides; D010671:Phenylurea Compounds; D014874:Water Pollutants, Chemical