title: Efficiency and degradation products elucidation of the photodegradation of mefenpyrdiethyl in water interface using TiO2 P-25 and Hombikat UV100.
abstract: The photodegradation of mefenpyrdiethyl (MFD), an herbicide safener, was investigated in aqueous suspensions by using Degussa P-25 and Hombikat UV100 titanium oxide under simulated sunlight irradiation. The effects of initial concentration of the herbicide, pH, catalysts and hydrogen peroxide doses as well as their combinations were studied and optimized. Accordingly, the kinetic parameters were determined and the effectiveness of the processes was assessed by calculating the rate constants. A pseudo first-order kinetics was observed. Under experimental conditions, the degradation rate constants were strongly influenced using P-25 and no noticeable effect was observed for Hombikat UV100. DFT calculations with B3LYP/6-311+G(2d,p)//B3LYP/6-31+G(d,p) level of theory were performed to check whether significant conformational changes occur when the charge state of the MFD substrate changesand whether these changes could play a role in the dependency of photodegradation rate constant on the studied pH. High resolution mass spectrometry (FT-ICR/MS) was implemented to identify the main degradation products.
authors.affiliation: Department of BioGeoChemistry and Analytik, German Research Center for Environmental Health, Helmholtz Center Munich, Ingoldstädter Landstrasse 1, D-85764 Neuherberg, Germany. amina.chnirheb@helmholtz-muenchen.de
authors.forename: Amina
authors.initials: A
authors.lastname: Chnirheb
authors.forename: Mourad
authors.initials: M
authors.lastname: Harir
authors.forename: Basem
authors.initials: B
authors.lastname: Kanawati
authors.forename: Azzouzi Mohammed
authors.initials: AM
authors.lastname: El
authors.forename: Istvan
authors.initials: I
authors.lastname: Gebefügi
authors.forename: Philippe
authors.initials: P
authors.lastname: Schmitt-Kopplin
mesh_terms: D002384:Catalysis; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D010575:Pesticides / Q000737:chemistry*; D055668:Photochemical Processes; D011720:Pyrazoles / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: C555731:1-(2, 4-dichlorophenyl)-4, 5-dihydro-5-methyl-1H-pyrazole-3,5-dicarboxylic acid diethyl ester; D010575:Pesticides; D011720:Pyrazoles; D014874:Water Pollutants, Chemical; D014867:Water; C009495:titanium dioxide; D014025:Titanium