Measurement and correlation of osmotic coefficients of aqueous solutions of imidazolium-based ionic liquids at different temperatures

Ionic liquids (ILs) are new class of organic salts purely ionic, saltlikematerials with a melting point below 100oC. Their importantproperties are negligible vapor pressure, good thermal stability, awide liquid range, suitable viscosity and nonflammable. They canreplace for toxic, flammable traditional volatile organic solvents inmany research and industrial applications.Osmotic coefficients for ionic liquid containing systems are of greatimportance in design of chemical processes such as separationprocesses, special distillation processes, e.g., extractive,understanding molecular interactions between ionic liquids andsolvent, applicability of thermodynamic models specific to ILcontainingsystems, prediction of VLE behaviour of ionic liquidsmixtures and heat transfer media.In this work we have measured osmotic coefficient data of aqueoussolutions of two ionic liquids 1-butyl-3-methylimidazolium chloride[BMIm]Cl, and 1-butyl-3-methylimidazolium iodide [BMIm]I,using vapor pressure osmometry (VPO) method at temperatures T =(298.15 to 328.15) K in interval 10 K. Theses data have beencorrelated with Clegg-Pitzer [3] and one local composition model,the MSA-NRTL models [4] using nonlinear least square method.