Kinetics & mechanism of oxidation of indigo carmine dye with potassium peroxydisulphate in micellar and sub –micellar medium

Abstract

Oxidation of Indigo carmine with potassium peroxydisulphate is investigated in presence of micelles under pseudo first order conditions in acidic medium. The reactants form suspensions with CTAB micelles under the established experimental conditions. There is no appreciable change in the rate with varying [Triton-X-100]. The reaction has shown first order kinetics with varying [Indigo carmine], [S₂O₈²⁻] and is independent of varying [H⁺] in presence of anionic SDS and neutral Triton-X-100 micelles. The ionic strength is maintained using sodium perchlorate, and there is no ionic strength effect on the rate of the reaction.The rate of the reaction is accelerated with varying [SDS], reaching a maximum under a sub-micellar concentration of 7.0 × 10⁻⁴ moldm⁻³. At higher SDS concentrations, the reaction rate is inhibited. The rate [surfactant] profile is showing a maximum, so the reaction is a typical bimolecular catalyzed reaction. The binding constant is determined by applying Piszkiewicz and Berezin kinetic models.