OXIDANT EFFICIENCY IN THE DEGRADATION OF ORANGE G BY FENTON OXIDATION

L. I. DOUMIC; M. C. CASSANELLO; M.A. AYUDE; P. M. HAURE

Río de Janeiro

Encuentro; VI Encontro sobre Aplicações Ambientais de Processos Oxidativos Avançados; 2011

Among the Advanced Oxidation Processes, Fenton´s reaction is very appealing because of its simplicity and the low price, availability and small toxicity of its reagents. In an acidic aqueous system containing an organic substrate, the ferrous ion initiates and catalyses the decomposition of H2O2, resulting in the generation of hydroxyl radicals, OH•. Once radicals are formed, they can react either with an organic, leading to an oxidized species; with unreacted hydrogen peroxide or with other radicals, leading in this case to inactive molecular oxygen, or with the metal (scavenger reactions). The parasitic reactions affect the overall degradation efficiency and may cause significant increase of operational costs. In this work, homogeneous Fenton oxidation of Orange G (OG) is investigated. The effect of N2 or air bubbling and reaction temperature on Total Organic Carbon (TOC) and H2O2 decomposition and efficiency is addressed. Dissolved oxygen concentration is monitored as an indication of the efficient use of the H2O2 in the process. Homogeneous Fenton oxidation of an azo dye (OG) 0.3mM solution with [Fe+2](0.45mM) is studied under different experimental conditions. When the hydrogen peroxide is fed at the stoichiometric requirement, higher temperatues improve both the mineralization and the hydrogen peroxide efficiency. Increasing the oxidant concentration beyond the theoretical stoichiometric ratio mainly enhances side reactions, thus reducing the hydrogen peroxide efficiency. Air bubbling slightly enhances mineralization mostly due to the presence of oxygen during the earliest stage of the experiment.