Mineralization of desmetryne by electrochemical advanced oxidation processes using a boron-doped diamond anode and an oxygen-diffusion cathode.

Núria Borràs, Conchita Arias, Ramon Oliver, Enric Brillas

Unitat de Química Industrial, Escola Universitàtia d'Enginyeria Tècnica Industrial de Barcelona, Universitat Politècnica de Catalunya, Comte d'Urgell 187, Barcelona, Spain.

Chemosphere 2011 Nov

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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)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. Copyright © 2011 Elsevier Ltd. All rights reserved.

Citation

Núria Borràs, Conchita Arias, Ramon Oliver, Enric Brillas. Mineralization of desmetryne by electrochemical advanced oxidation processes using a boron-doped diamond anode and an oxygen-diffusion cathode. Chemosphere. 2011 Nov;85(7):1167-75