title: Solar photoelectro-Fenton degradation of the herbicide 4-chloro-2-methylphenoxyacetic acid optimized by response surface methodology.
abstract: A central composite rotatable design and response surface methodology (RSM) were used to optimize the experimental variables of the solar photoelectro-Fenton (SPEF) treatment of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA). The experiments were made with a flow plant containing a Pt/air-diffusion reactor coupled to a solar compound parabolic collector (CPC) under recirculation of 10 L of 186 mg L(-1) MCPA solutions in 0.05 M Na(2)SO(4) at a liquid flow rate of 180 L h(-1) with an average UV irradiation intensity of about 32 Wm(-2). The optimum variables found for the SPEF process were 5.0 A, 1.0mM Fe(2+) and pH 3.0 after 120 min of electrolysis. Under these conditions, 75% of mineralization with 71% of current efficiency and 87.7 k Wh kg(-1) TOC of energy consumption were obtained. MCPA decayed under the attack of generated hydroxyl radicals following a pseudo-first-order kinetics. Hydroxyl radicals also destroyed 4-chloro-2-methylphenol, methylhydroquinone and methyl-p-benzoquinone detected as aromatic by-products. Glycolic, maleic, fumaric, malic, succinic, tartronic, oxalic and formic acids were identified as generated carboxylic acids, which form Fe(III) complexes that are quickly photodecarboxylated by the UV irradiation of sunlight at the CPC photoreactor. A reaction sequence for the SPEF degradation of MCPA was proposed.
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: Sergi
authors.initials: S
authors.lastname: Garcia-Segura
authors.forename: Lucio Cesar
authors.initials: LC
authors.lastname: Almeida
authors.forename: Nerilso
authors.initials: N
authors.lastname: Bocchi
authors.forename: Enric
authors.initials: E
authors.lastname: Brillas
mesh_terms: D008456:2-Methyl-4-chlorophenoxyacetic Acid / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D006540:Herbicides / Q000737:chemistry*; D007700:Kinetics; D010777:Photochemistry; D012996:Solutions; D013472:Sunlight
chemical_list: D006540:Herbicides; D012996:Solutions; D008456:2-Methyl-4-chlorophenoxyacetic Acid