title: Mineralization of desmetryne by electrochemical advanced oxidation processes using a boron-doped diamond anode and an oxygen-diffusion cathode.
abstract: The mineralization of acidic aqueous solutions of the herbicide desmetryne has been studied by electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation with electrogenerated H(2)O(2) (AO-H(2)O(2)), electro-Fenton (EF) and photoelectro-Fenton (PEF) with UVA light. Electrolyses were conducted in an open and cylindrical cell with a boron-doped diamond (BDD) anode and an O(2)-diffusion cathode for H(2)O(2) generation. The main oxidizing species are ()OH radicals formed at the BDD surface in all treatments and in the bulk from Fenton's reaction between added Fe(2+) and electrogenerated H(2)O(2) in EF and PEF. A poor mineralization was attained using AO-H(2)O(2) by the slow oxidation of persistent by-products with ()OH at the BDD surface. The synergistic action of ()OH in the bulk enhanced the degradation rate in EF, although almost total mineralization was only achieved in PEF due to the additional ()OH generation and photolysis of intermediates by UVA irradiation. The effect of current, pH and herbicide concentration on the mineralization degree and mineralization current efficiency of each EAOP was examined. Desmetryne decay always followed a pseudo first-order kinetics, being more rapidly destroyed in the sequence AO-H(2)O(2)<EF<PEF. In all EAOPs, ammeline and cyanuric acid were identified as persistent heteroaromatic by-products and oxamic and formic acids were detected as generated carboxylic acids. The generation of cyanuric acid mainly by oxidation with ()OH at the BDD surface is the predominant path for desmetryne degradation. The initial nitrogen of desmetryne yielded NO(3)(-) ion in low proportion and NH(4)(+) ion in much lesser extent, suggesting that its major part was lost as volatile N-derivatives.
authors: Unitat de Química Industrial, Escola Universitàtia d'Enginyeria Tècnica Industrial de Barcelona, Universitat Politècnica de Catalunya, Comte d'Urgell 187, Barcelona, Spain.
authors: Núria
authors: N
authors: Borràs
authors: Conchita
authors: C
authors: Arias
authors: Ramon
authors: R
authors: Oliver
authors: Enric
authors: E
authors: Brillas
mesh_terms: D001895:Boron / Q000737:chemistry*; D018130:Diamond / Q000737:chemistry*; D004058:Diffusion; D055664:Electrochemical Techniques; D004566:Electrodes; D052918:Environmental Restoration and Remediation; D005296:Ferrous Compounds / Q000737:chemistry; D006540:Herbicides / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010782:Photolysis; D014227:Triazines / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D005296:Ferrous Compounds; D006540:Herbicides; D014227:Triazines; D017665:Hydroxyl Radical; C009232:semeron; D018130:Diamond; D006861:Hydrogen Peroxide; D001895:Boron; D010100:Oxygen