Metanil yellow (MY) is a mono azo dye and used as a colorant agent in many food industries. It is extensively used in the developing countries as a colorant in sweet meat, ice-creams, soft drinks, and beverages.The kinetics of the oxidative degradation of an azo dye MY was investigated in aqueous solution using dirhodium(II) caprolactamate, Rh2(cap)4, as a catalyst in the presence of H2O2 as oxidizing agent.The reaction process was followed by UV/Vis spectrophotometer. The decolorization and degradation kinetics were investigated and both followed a pseudo-first-order kinetic with respect to the [MY]. The effects of various parameters such as H2O2 and dye concentrations, the amount of catalyst and temperature have been studied. The studies show that Rh2(cap)4 is a very effective catalyst for the formation of hydroxyl radicals HO• which oxidized and degraded about 92% of MY into CO2 and H2O after 24 h as measured by total carbon analyzer.
Though there are very few reports on the study of oxidation/degradation of MY, there are no reports dealing with the oxidative decolorization of MY with any oxidants from the kinetic and mechanistic view points. Hence the mechanism and rate law were obscure.