Ozonation of reactive dye, Procion red MX-5B catalyzed by metal ions

Ozonation of aqueous solution of Procion redMX-5B, a commercial azo reactive dyewas investigated. The effect of various experimental variables on decolorization and degradation of the dye has been studied. Color removal was faster than organic removal. Dye mineralization was evident by the generation of sulphate, chloride, nitrate, oxalic and acetic acid during ozonation. The decolorization and organic removal followed pseudo-first-order kinetics. Among the metal ions studied, manganese catalyzed ozonation showed better decolorization and organic removal. Fourier transform infrared (FTIR) spectroscopy results indicated the disappearance of bands for aromatics and appearance of bands due to carboxylic acids in the ozonated samples. Acetyl benzoic acid, diethyl phthalate and phthalic anhydride were identified as intermediates by gas chromatography mass spectra (GC/MS). Based on these findings a tentative pathway for the degradation MX-5B was postulated

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 Fe2þ, 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 Fe2þ 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 grou