Decolorization kinetics and mechanisms of mono azo dyes by CAB/HClO 4 /Ir(III) redox system


Adalagere Somashekar Manjunatha, K. Krishnaveni, P. R. Koushalya
Department of Chemistry, Don Bosco Institute of Technology, (Affiliated to Visvesvaraya Technological University -Belagavi), Mysore Road, Kumbalagodu, Bengaluru-560 074, India.
Anu Sukhdev
Department of Chemistry, Presidency University, Bengaluru-560 089, India.


Decolorization is proven to be the most efficient, eco-friendly and cost effective technique for the decolorization of dyes in wastewater. In this work, oxidative decolorization of azo dyes viz. Methyl orange (MO) and Ethyl Orange (EO) by CAB/ HClO4/Ir(III), was studied. Variation of dye, oxidant, catalyst and acid concentrations on the rate of decolourization was carried out. Under optimal experimental conditions, 85% decolorizations of dyes are achieved in 80 minutes and in the presence of Iridium tri chloride (Ir(III)), it has been drastically reduced to 20 minutes. Hence Ir(III), catalyst is proved to be an efficient homogenous catalyst in the present kinetic redox system. Kinetic rate law and mechanistic pathway have been deduced. Mass spectral analysis was utilized for the identification of degradation products. COD and phytotoxicity analysis revealed that degradation products were less toxic as compared to the original dyes.