Quantitative Analysis of Dye Decolourization Reactions in Mixed Micellar Systems of Sodium Dodecyl Sulfate with Tween-20, Tween-80, and Triton X-100

Abstract

The reaction of triphenylmethane dye (ethyl violet) with hydroxyl ion has been investigated in absence and presence of micelles. In micellar solutions, the solubilization of dye carbocation is observed. The reaction rate constant follows pseudo-first order kinetics with respect to the nucleophile. In presence of sodium dodecyl sulfate (SDS) micelles, an inhibitory effect is observed due to repulsion of the nucleophile to the strongly bound dye carbocation in the negatively charged SDS aggregate. The presence of nonionic surfactant reduces the inhibitory effect of the anionic SDS micelles. Quantitative analysis of the micellar data obtained has been done by applying a positive cooperativity model of enzyme catalysis. The value of n (index of cooperativity) has been found to be greater than 1 for all systems under study. The presence of solvents such as ethanol, n-propanol, and n-butanol reduces the inhibitory effect of the micelles.