Oxidative degradation of direct orange 61 by electro-Fenton process using a carbon felt electrode: Application of the experimental design methodology

The degradation of an azo dye, the direct orange 61 (DO 61), has been studied by electro-Fenton process using a Pt anode and a carbon felt cathode. The great oxidation ability of this process is due to the large production of hydroxyl radicals ((OH)-O-center dot) in the medium from electrochemically assisted Fenton's reaction which takes place between electrogenerated H2O2 and Fe2+ formed by cathodic reduction of O-2 and Fe, respectively. These radicals are able to oxidize any organics until their mineralization. A factorial experimental design was used for determining the influent parameters on the DO 61 degradation in aqueous medium by electrochemically generated (OH)-O-center dot radicals. The results obtained have shown that the current intensity and the dye initial concentration were the main influent parameters on the degradation rate. Thus, under the obtained conditions, kinetic analysis of DO 61 degradation showed a pseudo-first order reaction. The optimal experimental parameters for DO 61 mineralization have been investigated by the use of Doehlert matrix. It has been demonstrated that under the optimal conditions determined by this method, electro-Fenton process can lead to a complete mineralization of the dye solution after 6 h (98% of TOC removal) giving carboxylic acids and inorganic ions as final end-products before mineralization. The results show the efficiency of the electro-Fenton process to remove organic pollutants from aqueous medium. (C) 2007 Elsevier B.V. All rights reserved.