Removal of Acid Orange 7 from water by electrochemically generated Fenton's reagent

The removal of azo dye Acid Orange 7 (AO7) from water was investigated by the electro-Fenton technology using electrogenerated hydroxyl radicals ((OH)-O-center dot) which leads to the oxidative degradation of AO7 LIP to its complete mineralization. H2O2 and Fe (II) ions are electrogenerated in a catalytic way at the carbon-felt cathode. AO7 decay kinetics and evolution of its oxidation intermediates were monitored by high-performance liquid chromatography. The absolute rate constant of AO7 hydroxylation reaction has been determined as (1.20 +/- 0.17) x 10(10) M-1 s(-1). The optimal Current value for the degradation of AO7 was found as 300 mA. AO7 degradation rate was found to decrease by increase in Fe3+ concentration beyond 0.1 mM. Mineralization of AO7 aqueous solutions was followed by total organic carbon (TOC) measurements and found to be 92%. Based on TOC evolution and identification of aromatic intermediates, short-chain carboxylic acids and inorganic ions released during treatment, a plausible mineralization pathway was proposed. (C) 2008 Elsevier B.V. All rights reserved.