Phase Diagrams for the Aqueous Two-Phase Ternary System Containing the Ionic Liquid 1-Butyl-3-methylimidazolium Bromide and Tri-potassium Citrate at T = (278.15, 298.15, and 318.15) K

摘要

Liquid—liquid equilibria (LLE) for the aqueous 1-butyl-3-methylimidazolium bromide ([C4mim]Br) + tri-potassium citrate system have been experimentally determined at T= (278.15, 298.15, and 318.15) K. An empirical nonlinear expression developed by Merchuk was used for reproducing the experimental binodal data. In this work, the three fitting parameters of the Merchuk equation were obtained with the temperature dependence expressed in the linear form with (T — T0) K as a variable. The effect of temperature on the phase-forming ability in the investigated system has also been studied on the basis of a salting-out coefficient obtained from fitting the tie-line data to a Setschenow-type equation for each temperature. The values of the salting-out coefficients may reflect the extent of the preferential hydration of the ionic liquid. Furthermore, the kosmotropicity of tri-potassium citrate for the exclusion of [C4mim][Br] in an aqueous solution has been examined in comparison with the previously studied kosmotropic salts on the basis of the ionic viscosity B coefficients of salt constituent anions and the preferential hydration of the ionic liquid.