Surface tension measurements of aqueous 1-alkyle-3-methylimidazolume tetrafluoroborate {[Cnmim][BF4] (n = 2, 4, 6)} solutions and modeling surface tension of ionic liquid binary mixtures using six various models

Abstract

The surface tension of three ionic liquids: [C2mim][BF4] (1-ethyl-3-methylimidazolium tetrafluoroborate), [C4mim][BF4] (1-butyl-3-methylimidazolium tetrafluoroborate) and [C6mim][BF4] (1-hexyl-3-methylimidazolium tetrafluoroborate) blended with water were measured at temperatures from (298.15 K to 338.15) K and whole range of mole fraction. The measurements show that studied systems are highly nonideal and surface tension decrease as temperature rises in a linear order. In following, to describe the surface tension of the solutions as a function of temperature and concentration, simultaneously, a new model based on thermodynamics was developed using the nonelectrolyte NRTL nonrandom factor (N-NRTL-NRF) equation. Also, a comprehensive dataset consist of 19 binary ionic liquid solutions with 989 data points at various conditions was collected. The new model, as well as five other models, were applied to the dataset and the performance of the six models was compared to experiments and to each other. The new model shows a deviation with the experiment as RMSD = 0.4559%.