RESEARCH • CHEMISTRY

Reactive dyes are the largest single group of dyes used in the textile industry and have been selected for our study because refractory azo-dye compounds used in the texture industry are commonly detected in texture wastewater. In this study the oxidative degradation of methyl orange, one of azo-dyes, with hexacyanoferrate(abbreviated as MO and HCF respectively)(III) in aqueous alkaline media at constant ionic strength and temperature has been studied spectrophotometrically. The results show that the reaction rate follows first order kinetics with respect to hexacyanoferrate(III), methyl orange and hydroxide ions concentration. The linear plots between log (-dc/dt) and µ suggest positive salt effect i.e. involvement of two similarly charged species in the rate determining effect. Thermodynamic parameters were evaluated by studying the reaction at four different temperatures between 400 to 550 under pseudo order conditions. Large value of energy of activation suggests low rate of degradation of methyl orange. A mechanism for dye oxidation in alkaline media is also proposed