A novel method for oxidative degradation of metanil yellow azo dye by hexacyanoferrate(III) ions.

In the present work, the degradation of metanil yellow, an azo dye, by hexacyanoferrate(III) ions (oxidant) in the aqueous alkaline medium has been investigated by kinetic-spectrophotometric method at λmax 435 nm of the reaction mixture. The effect of various parameters such as the concentration of dye, oxidant, and solution pH on the reaction rate has been determined. The results show that the rate of degradation increases linearly with the increase in concentrations of oxidant and dye at optimum pH of 9.0 and constant temperature of 40 ± 0.1°C. Thermodynamic parameters such as energy of activation, enthalpy of activation, entropy of activation, and energy of formation have been calculated by studying the reaction rate at four different temperatures, that is, 40-55°C. Based on the experimental results, a plausible reaction mechanism involving complex formation has been proposed and a rate law has been derived. UV-Vis and LC-MS methods of analysis of degradation products show the formation of simpler and less hazardous degradation products. PRACTITIONER POINTS: It is also observed that the time required for azo dye degradation by the present method is about ten times less than the reported methods. Thus degradation of azo linkage and formation of simple and less hazardous products (efficient degradation of dye) makes it a novel method.