title: Degradation of clofibric acid in acidic aqueous medium by electro-Fenton and photoelectro-Fenton.
abstract: Acidic aqueous solutions of clofibric acid (2-(4-chlorophenoxy)-2-methylpropionic acid), the bioactive metabolite of various lipid-regulating drugs, have been degraded by indirect electrooxidation methods such as electro-Fenton and photoelectro-Fenton with Fe(2+) as catalyst using an undivided electrolytic cell with a Pt anode and an O(2)-diffusion cathode able to electrogenerate H(2)O(2). At pH 3.0 about 80% of mineralization is achieved with the electro-Fenton method due to the efficient production of oxidant hydroxyl radical from Fenton's reaction between Fe(2+) and H(2)O(2), but stable Fe(3+) complexes are formed. The photoelectro-Fenton method favors the photodecomposition of these species under UVA irradiation, reaching more than 96% of decontamination. The mineralization current efficiency increases with rising metabolite concentration up to saturation and with decreasing current density. The photoelectro-Fenton method is then viable for treating acidic wastewaters containing this pollutant. Comparative degradation by anodic oxidation (without Fe(2+)) yields poor decontamination. Chloride ion is released during all degradation processes. The decay kinetics of clofibric acid always follows a pseudo-first-order reaction, with a similar rate constant in electro-Fenton and photoelectro-Fenton that increases with rising current density, but decreases at greater metabolite concentration. 4-Chlorophenol, 4-chlorocatechol, 4-chlororesorcinol, hydroquinone, p-benzoquinone and 1,2,4-benzenetriol, along with carboxylic acids such as 2-hydroxyisobutyric, tartronic, maleic, fumaric, formic and oxalic, are detected as intermediates. The ultimate product is oxalic acid, which forms very stable Fe(3+)-oxalato complexes under electro-Fenton conditions. These complexes are efficiently photodecarboxylated in photoelectro-Fenton under the action of UVA light.
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.forename: Conchita
authors.initials: C
authors.lastname: Arias
authors.forename: Pere Lluís
authors.initials: PL
authors.lastname: Cabot
authors.forename: Francesc
authors.initials: F
authors.lastname: Centellas
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Garrido
authors.forename: Rosa María
authors.initials: RM
authors.lastname: Rodríguez
authors.forename: Enric
authors.initials: E
authors.lastname: Brillas
mesh_terms: D002995:Clofibric Acid / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods; D008401:Gas Chromatography-Mass Spectrometry; D006861:Hydrogen Peroxide / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010777:Photochemistry / Q000379:methods; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D014876:Water Pollution / Q000517:prevention & control*
chemical_list: C045076:Fenton's reagent; D014874:Water Pollutants, Chemical; D002995:Clofibric Acid; D006861:Hydrogen Peroxide; D007501:Iron