Estimation of Surface Tension of Ionic Liquid-Cosolvent Binary Mixtures by a Modified Hildebrand-Scott Equation

The correlation model of gas-liquid interfacial tension (surface tension) of nonaqueous mixtures containing ionic liquids (ILs) is still in its infancy. The purpose of this work is to develop a modified Hildebrand-Scott equation based on local composition concept and the group surface area parameters of UNIFAC model as well as to evaluate the capability of this model. The surface tension of 33 IL-cosolvent binary systems were correlated by the modified Hildebrand-Scott equation with two energy parameters and an overall average relative deviation of only 0.92%. The ILs in the study included imidazolium-based, pyridinium-based, and isoquinolinium-based ones, and the cosolvents included methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, acetonitrile, and tetrahydrofuran. Using the energy parameters obtained from the surface tension of a given IL-cosolvent binary system at 298.15 K, the surface tension of the same system at other different temperatures was predicted by the modified Hildebrand-Scott equation, with an overall average relative deviation of 1.06%.