Interaction of Cationic and Anionic Surfactants in Pure Water and Methanol-Water Mixed Solvent Media

Abstract

The properties of anionic-rich and cationic-rich mixtures of DTAB (Dodecyltri-methylammonium bromide) and SDS (Sodiumdodecyl sulfate) in pure water and methanol-water mixed solvent media were studied by measuring the conductivity, density and surface tension at room temperature. Various physico-chemical properties like cmc, thermodynamic parameters (∆Gm, α) and surface activity parameters (Гmax, Amin) were evaluated. The result showed that sharp increased in conductance with increasing the concentration of surfactant mixtures, were found to decrease with increasing methanol content in the solvent composition. The density was almost increased and surface tension was initially decreased with increasing concentration of surfactants for both the anionic-rich and the cationic-rich mixtures. With increasing methanol content in the solvent composition, critical micelle concentration (cmc) of the mixed surfactants increased for conductance, density and surface tension measurements. The degree of micellar dissociation (α) was found to be increased whereas the surface excess concentration (Гmax) was found to be decreased. However, the increase in minimum area per molecule was seen with increasing in volume fraction of the methanol for both the anionic-rich and cationic-rich systems.