Surface tension of mixtures containing ionic liquids based on an equation of state and on the geometric similitude concept

A model based on a cubic equation of state and on the geometric similitude concept is proposed to calculate the surface tension of pure substances and mixtures containing organic substances, water, and ionic liquids. The geometric similitude is observed between surface tension and density for liquid mixtures at different temperatures and concentrations. The parameters of the model have been estimated by fitting experimental pure component data obtained from the literature. The model has been extended to binary and ternary mixtures using simple mixing and combining mixing rules without interaction parameters, so the predictive capabilities of the model are guaranteed. Data for 90 binary mixtures (2660 data) and 12 ternary mixtures (467 data) are considered. The mixtures are composed of organic solvent + ionic liquid and water + ionic liquids. The temperature varies from 278.15 to 348.15 K in the whole composition range at atmospheric pressure. Various form of estimating the necessary pure component parameters are analyzed. Results show that the model is accurate for primary estimation in process design and process simulation.