Decomposition of a Di Azo Dye in aqueous solutions by

Abstract

This study examined the photolytic degradation of C.I. Acid Red 73 AR73 diazo dye, in aqueous solution by combined UV, hydrogen peroxide and KMnO4. A continuous circulated photoreactor equipped with a low pressure mercury lamp 15 W, emission 253.7 nm was used. In the first step, potassium permanganate was used for decolourisation of AR73 dye solution. The effect of the key operating variables such as initial dye concentration, permanganate amount, pH and temperature were studied. In order to avoid the overdose of KMnO4, the stoichiometric amount of permanganate required for 1 mol of AR73 complete colour removal was determined 2.79 mol. Dye degradation efficiency was studied by monitoring Total Organic Carbon TOC at different UV irradiation times. In the acidic solution, 100 of AR73 colour removal and near 10 dye mineralization have been observed in no more than 5 minutes. In the second step, after decolourisation period, UV/H2O2 system was applied for mineralization of the dye solution. In the best operational conditions, after 180 minutes of UV irradiation time, we have observed 90 of dye mineralization. In the third step, the results of this method were compared with which obtained by using UV/H2O2 system without KMnO4 oxidative pre-treatment. It was found that under the same irradiation time 180 min, KMnO4/UV/H2O2 process is about 10 more effective for mineralization of AR73 dye solution.