Oxidative Decolourisation of Food Dye, Quinoline Yellow in the Presence of Sodium Hydroxide and in Hydrochloric Acid Catalyzed By H⁺: A Kinetic and Mechanistic Approach

Background: Synthetic dyes have attracted significant attention in the leather tanning, textile, paper and pulp as well as in the food industry. As most of the synthetic dyes are nonecofriendly, numerous methods have been devised to treat such water in low cost. Oxidation kinetics of food dye i.e. Quinoline Yellow (QY) by Chloramine-T (CAT) in both acidic and alkaline media has been investigated using conventional spectrophotometric technique. Method: The experimental rate law was found to be –d[CAT]/dt = k[QY][CAT]1[H+]y[PTS]-Z, –d[CAT]/dt= k[QY][CAT]1[OH-]-y[PTS]-Z in acid and alkaline medium, respectively. Result: Increasing ionic strength had no effect on the rate of the reaction and also the solvent isotopic effect was examined. The dielectric effect and reduction product, ptoluenesulphonamide (PTS) was negative. The reaction was studied at different temperatures and the activation parameters were computed. The result of this study helped in deducing the plausible mechanism and rate law.