Modeling Interfacial Tension in Liquid–Liquid Systems Containing Electrolytes

Abstract

A comprehensive model has been developed for calculating the interfacial tension (σ) in liquid–liquid systems with or without electrolyte components. The model consists of an equation for computing the interfacial tension of two-liquid-phase nonelectrolyte systems and an expression for the effect of the electrolyte concentration. The dependence of the interfacial tension on the electrolyte concentration was derived by combining the Gibbs equation with a modified Langmuir adsorption isotherm that represents the interfacial excess of the solute species. The Langmuir adsorption formalism was extended by introducing the effects of binary interactions between solute species (ions or molecules) on the interface. The equation for the interfacial tension of nonelectrolyte liquid–liquid systems was derived using a general thermodynamic framework that was empirically extended by introducing an effective interfacial area that is defined for each component and takes into account the effects of other components at the...