A molecular thermodynamic model for interfacial tension in surfactant-oil-water system

An interfacial equation of state based on perturbation theory for surfactan t-oil-water system has been developed. By combining the interfacial equatio n of state with Boudh-Hir and Mansoori's model, a molecular thermodynamic m odel has been proposed. The interfacial tension of surfactant-oil-water sys tems can be calculated from the surface tensions of pure oil and water by t his model. The interfacial tension data for sodium dodecyl sulphate-heptane -water system, polyoxyethylene n-octylphenol-heptane-water system and hexad ecyl trimethyl ammonium bromide-heptane-water system have been correlated. By using the adjustable parameters obtained, the interfacial tensions of th ese systems at other temperatures have been predicted. Both the correlated and the predicted values are satisfactory.