title: Application of electrochemical advanced oxidation processes to the mineralization of the herbicide diuron.
abstract: Here, solutions with 0.185mM of the herbicide diuron of pH 3.0 have been treated by electrochemical advanced oxidation processes (EAOPs) like electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and UVA photoelectro-Fenton (PEF) or solar PEF (SPEF). Trials were performed in stirred tank reactors of 100mL and in a recirculation flow plant of 2.5L using a filter-press reactor with a Pt or boron-doped diamond (BDD) anode and an air-diffusion cathode for H2O2 electrogeneration. Oxidant hydroxyl radicals were formed from water oxidation at the anode and/or in the bulk from Fenton's reaction between added Fe(2+) and generated H2O2. In both systems, the relative oxidation ability of the EAOPs increased in the sequence EO-H2O2<EF<PEF or SPEF. The two latter processes were more powerful due to the photolysis of intermediates by UV radiation. In the stirred tank reactor, the PEF treatment with BDD was the most potent method, yielding 93% mineralization after 360 min at 100 mA cm(-2). In the flow plant, the SPEF process attained a maximum mineralization of 70% at 100 mA cm(-2). Lower current densities slightly reduced the mineralization degree in SPEF, enhancing the current efficiency and dropping the energy consumption. The diuron decay always obeyed a pseudo-first-order kinetics, with a much greater apparent rate constant in EF and SPEF compared to EO-H2O2. Oxalic and oxamic acids were detected as final carboxylic acids. Ammonium and chloride ions were also released, the latter ion being partially converted into chlorate and perchlorate ions at the BDD surface.
authors.affiliation: Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain; Departamento de Química, Laboratório de Eletrocatálise e Eletroquímica Ambiental, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo (FFCLRP, USP), Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil.
authors.forename: Angelo R F
authors.initials: AR
authors.lastname: Pipi
authors.affiliation: Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
authors.forename: Ignasi
authors.initials: I
authors.lastname: Sirés
authors.affiliation: Departamento de Química, Laboratório de Eletrocatálise e Eletroquímica Ambiental, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo (FFCLRP, USP), Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil.
authors.forename: Adalgisa R
authors.initials: AR
authors.lastname: De Andrade
authors.affiliation: Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain. Electronic address: brillas@ub.edu.
authors.forename: Enric
authors.initials: E
authors.lastname: Brillas
mesh_terms: D004237:Diuron / Q000737:chemistry*; D055664:Electrochemical Techniques; D004566:Electrodes; D006540:Herbicides / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D010084:Oxidation-Reduction; D010782:Photolysis; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification
chemical_list: C045076:Fenton's reagent; D006540:Herbicides; D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical; D004237:Diuron; D006861:Hydrogen Peroxide; D007501:Iron
keywords: Diuron; Electro-Fenton; Electrochemical oxidation; Solar photoelectro-Fenton; Water treatment