A density functional theory based on the perturbed-chain polar statistical associating fluid theory (PCP-SAFT) is extended to mixtures. The Helmholtz energy functional is suitable for inhomogeneous fluid phases and is here applied to vapor− liquid systems. The attractive branch of the van der Waals attractions are treated with a perturbation theory of first order in a nonmean field approach. The radial distribution function is considered in the Percus−Yevick closure for chain fluids with a threefluid theory approach. This perturbation term is brought to consistency with the PCP-SAFT equation of state using the approach of Gloor et al. [Gloor, G.

The interfacial tensions of liquid−liquid mixtures are rarely measured, despite their importance, for example, in extraction processes. In this work, we applied classical density functional theory to liquid−liquid interfaces of binary mixtures and evaluated the predicted interfacial tensions. The functional was based on the statistical associating fluid theory with a polar perturbed-chain contribution to the dispersive term (PCP-SAFT). To ensure a good representation of the liquid−liquid equilibrium of the bulk phases, we applied two binary interaction parameters. Interfacial tensions were predicted without adjusting any model parameter to interfacial properties. For several methanol and ethylene glycol systems, we found good agreement with existing experimental data on interfacial tensions. Limitations in the accuracy of the Helmholtz energy functional were seen for aqueous liquid mixtures, for which phase equilibria were not modeled with sufficient agreement to experimental data, preventing a meaningful prediction of interfacial tensions.

We present an approach to calculate interfacial resistivities against mass and heat transfer at a vapor–liquid interface. Classical density functional theory is combined with the perturbed chain statistical associating fluid theory (PC-SAFT) equation of state to calculate continuous density profiles and (partial molar) enthalpy profiles across the interface. We follow the approach of Glavatskiy and Bedeaux [Glavatskiy, K.; Bedeaux, D. J. Chem. Phys. 2010, 133, 144709] where the resistivity for heat and mass transport and the coupled resistivities of an interface are obtained by integrating over local resistivities across an interface. This formalism is applied to pure component systems and to binary mixtures. We compare our results to previously published results from nonequilibrium molecular dynamic (NEMD) simulations for argon and n-octane. Two constant parameters have to be adjusted to NEMD simulations for each local resistivity profile. Very good agreement was found for both pure component systems. The results for binary mixtures are in very satisfying agreement to results from NEMD simulations. This study is the first to combine a physically based approach with integral relations not only for model fluids but also for real components and binary mixtures.