Kinetics Study of Dye Decolorization by Oxidation in Aqueous and Aqueous Alcohol Medium

摘要

The kinetics of oxidation of methylene blue with potassium bromate was investigated by observing decolorization of methylene blue in aqueous, aqueous methanol and aqueous isopropanol solvent system. The rate of reaction was studied as function of concentrations of methylene blue and potassium bromate in acidic medium at temperature 303 and 313 K. The increase in concentration of potassium bromate enhances the rate of decolorization of methylene blue in acidic medium; no significant change in rate was observed with variation of methylene blue. The rate of decolorization was found to be fastest in aqueous methanol compared to aqueous isopropanol and slow in aqueous medium. From the investigation, it was observed the reaction follows pseudo-first-order kinetics. The kinetic data were used to propose the mechanism of reaction. Thermodynamic parameters, enthalpy of activation (Delta H*), entropy of activation (Delta S*) and Gibbs free energy of activation (Delta G*), were also calculated to support kinetic results.