New experimental and modeling based on the N-Wilson-NRF equation for surface tension of aqueous alkanolamine binary mixtures

In this work, surface tension of aqueous solutions of various alkanolamines; monoethanolamine (MEA), diethanolamine (DEA), diisopropanolamine (DIPA), N-methyldiethanolamine (MDEA) and Sulfolane at the temperature range of 298.15-348.15 K and mole fraction ranges of 0-1 are determined. In the studied temperature range, the experimental surface tension values of the binary mixtures increase as the water concentration increases and decrease as the temperature increases. In following, the surface tension results for the binary solutions were correlated simultaneously as a function of temperature and concentration. For this purpose based on a thermodynamic definition of surface tension and the expression of Gibbs free energy, a new surface tension equation is proposed. This new equation is developed by using the nonelectrolyte Wilson nonrandom factor (N-Wilson-NRF) model to represent the excess Gibbs free energy of the system. The model parameters obtained by correlating binary surface tension at two different approaches. In one approach the parameters are assumed as non-temperature dependent and in another approach, a linear temperature dependency is considered. The comparison between the results of the presented model with experimental data and four other models show that the new equation is simple and more accurate in the correlation of these studied systems.