Predictive model for the calculation of interfacial tension in nonideal electrolytic systems

A new model is proposed for the calculation of the interfacial tension between an organic solvent and concentrated aqueous solutions of electrolytes. The interfacial tension is derived from the isothermal Gibbs equation. The increase or decrease of interfacial tension with concentrations are modeled using a Langmuir-type adsorption equation and the strong non-ideality of the mixtures is taken. into account through the Mikulin equation. The model parameters are first determined with binary water-electrolyte solutions and are kept constant in the case of mixtures. The model has been applied to chloride solutions-chloride salts of various metals and hydrochloric acid-and compared with experimental data obtained by using the pendant drop technique and a Wilhelmy tensiometer. In all cases investigated, good agreement is observed, even in the case of stiff variations of interfacial tension with the electrolyte concentration and also at high concentrations Of electrolytes. (C) 1997 Academic Press.