Decolorization and degradation of H-acid and other dyes using ferrous–hydrogen peroxide system

In this study, advanced oxidation process utilizing Fenton’s reaction was investigated for the decolorization and degradation of two commercial dyes viz., Red M5B, Blue MR and H-acid, a dye intermediate used in chemical industries for the synthesis of direct, reactive and azo dyes. Effect of Fe2+, H2O2, pH, and contact time on the degradation of the dyes was studied. Maximum color and COD removal was obtained for Red M5B, H-acid and Blue MR at 10–25 mg/l of Fe2+ dose and 400–500 mg/l of H2O2 dose at pH 3.0. The initial oxidation reaction was found to fit into first order rate kinetics and the rate of oxidation of H-acid was higher than the other dyes. Release of chloride and sulfate from the Fenton’s treated Red M5B dye and sulfate from H-acid and Blue MR indicates that the dye degradation proceeds through cleavage of the substituent group.