INTERFACIAL-TENSION OF OIL BRINE SYSTEMS IN THE PRESENCE OF SURFACTANT AND COSURFACTANT

The aim of the present paper is to theoretically examine the variation of the interfacial tension between bulk oil and water phases in the presence of salt, surfactant, and cosurfactant. Here, a simple multicomponent adsorption isotherm is derived that takes into account the different sizes of the solutes and the interactions among them and the solvent. These simple adsorption isotherm equations yield both the interfacial tension and the surface phase concentrations as a function of bulk phase concentrations. The surfactant concentrations are chosen to be less than their respective critical micelle concentrations so that micellization in the bulk aqueous phase can be neglected. The interfacial tension has been calculated as a function of the concentrations of the surfactant, cosurfactant, and salt. This analysis can be applied to both nonionic and ionic surfactants.