Thermodynamics and Kinetic Investigations on the Interactions between Malachite Green and Cetyltrimethylammonium Bromide

Malachite green (MG) is a widely -used textile dye. It fades in the presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB) in aqueous solutions and in oil/water/surfactant microemulsions. The surfactant was treated as a reactant in this study, as there were direct interactions between MG and CTAB in these solutions. By measuring the absorbance of different MG aqueous solutions and microemulsions at the maximum absorbance wavelength, and using the appropriate association models to analyze the experimental data, a good linear relationship was observed between MG and CTAB. Association constants were obtained and the value of the thermodynamics function of association Delta(r)G(m) was calculated. It was concluded from these results that microemulsion formation had an inhibitory effect on the association reaction.