Application of the UNIFAC model for prediction of surface tension and thickness of the surface layer in the binary mixtures

The relative Gibbs adsorption, the surface mole fraction and the thickness of liquid–vapor interfaces as a function of composition have been evaluated using the UNIFAC model. [Display omitted] ► The activity coefficients of surface and bulk phases have been calculated by UNIFAC methods. ► Molar surface areas are evaluated based on Paquette areas and Rasmussen areas model. ► Surface mole fraction and relative Gibbs adsorption parameters have been calculated. ► The thickness of surface layer of mixtures has been calculated by UNIFAC method. Surface properties of binary mixtures of (alkanol with acetonitrile) have been measured by surface tension method at T = 298.15 K and atmospheric pressure. The UNIFAC method is used for calculation activity coefficients of surface and bulk phases. Also, the surface tension has been predicted based on the Suarez method. This method combines a model for the description of surface tension of liquid mixtures with a UNIFAC group contribution method for the calculation of activity coefficient. Two techniques for calculation of molar surface areas, based on Paquette areas and Rasmussen areas are tested. On comparing the computed values of surface tension by the present approaches with experimental data, satisfactory results have been observed. In addition, the relative Gibbs adsorption and the surface mole fraction have been evaluated using this model. It is possible to calculate the thickness of liquid–vapor interfaces starting from surface tension data. A novel procedure is developed to obtain the thickness of liquid–vapor interfaces as a function of composition in binary systems.