Experimental Determination and Correlation of Density and Viscosity for the Acetonitrile–Water Azeotropic System Containing [EMIM][OAc] and Glycolic Acid/Choline Chloride Deep Eutectic Solvent at Atmospheric Pressure

To enhance the separation efficiency of the acetonitrile–water azeotrope, the densities and viscosities of the azeotropic mixture with two entrainers─1-ethyl-3-methylimidazolium acetate ([EMIM][OAc], an ionic liquid) and a deep eutectic solvent (DES, denoted as GC3:1) prepared by glycolic acid and choline chloride at a molar ratio of 3:1─were experimentally determined at atmospheric pressure. Density measurements were performed over a wide composition range at temperatures from 283.15 to 333.15 K, while viscosity measurements were carried out at 293.15–333.15 K under the same composition range. Thermodynamic parameters including excess molar volume were calculated from the experimental density data. The experimental density and viscosity data were well correlated using empirical linear models, with high correlation coefficients. The addition of either entrainer significantly increased both the density and viscosity of the acetonitrile–water azeotrope. This work provides essential thermophysical data and thermodynamic parameters for acetonitrile recovery via extractive distillation, which offers valuable guidance for entrainer screening and process optimization in industrial applications.