Kinetic investigation of an azo dye oxidation by hydrogen peroxide in aqueous surfactant solution

Abstract

In this study, the oxidation of resorcinol based an azo dye, 5-methyl-4-(2-thiazolylazo)resorcinol (5-Me-TAR) by hydrogen peroxide has been investigated from kinetic, spectroscopic and thermodynamic point of view to examine the influence of a cationic surfactant such as cetylpyridiniumchloride (CPC). Activation energy (298.15–313.15 K) and entropy (298.15 K) of the reaction were calculated as 67 kJ/mol and −72 J mol −1 K −1 in borate buffer, respectively. However, the addition of CPC into 5-Me-TAR solutions at different pH values always reduced the intensity of its azo form, the intensity of its hydrazone form increased. The oxidation of dye proceeds via perhydroxyl anion and hydrazone tautomeric form and oxidation rate was accelerated by the presence of CPC either in micellar or premicellar regions.