Oxidative decolorization of indigo caramine dye with chloramine-T catalyzed by cobalt(II)

Decolorization of indigo caramine dye by oxidation process using chloramine-T as oxidant and Co(II) as catalyst in acidic buffer media, pH 5.8 has been kinetically studied at 300 K. Decolorization of indigo caramine dye was followed spectrophotometrically. Decolorization and oxidation led to a decrease in Chemical Oxygen Demand of the dye. The Co(II)-catalyzed reaction shows first-order dependence of the rate on chloramine-T and indigo caramine concentrations. It also shows fractional order dependence on Co(II)] and H⁺]. Addition of halide ions or reduction product of chloramine-T toluenesulfonamide, and variation of ionic strength and dielectric constant of the medium do not have any significant effect on the reaction rate. Activation parameters are evaluated from the Arrhenius plot, and a mechanism is proposed for the reaction.