Salting-Out Effect, Preferential Exclusion, and Phase Separation in Aqueous Solutions of Chaotropic Water-Miscible Ionic Liquids and Kosmotropic Salts: Effects of Temperature, Anions, and Cations

The phase diagrams and the liquid−liquid equilibrium (LLE) data of 1-butyl-3-methylimidazolium chloride ([C 4 mim]Cl) + tripotassium citrate and 1-butyl-3-methylimidazolium bromide ([C 4 mim]Br) + trisodium citrate aqueous two-phase systems (ATPS’s) were determined experimentally at T = (278.15, 298.15, and 318.15) K. The Merchuk equation with three dependent-temperature adjustable parameters was used for reproducing the binodal curves. In the studied systems, the salting-out effect caused by the addition of the inorganic salts to the aqueous solutions of the water-miscible ionic liquids (ILs) was investigated. The effects were analyzed using the corresponding composition phase diagrams. The effect of temperature on the phase-forming ability in the investigated systems was also evaluated based on a salting-out coefficient obtained from fitting the tie-line data to a Setschenow-type equation. The values of the salting-out coefficients may reflect the extent of the preferential hydration of the IL. Furthermore, the salting-out effect and the consequent phase separation in the investigated ATPS’s were interpreted taking into account the complex and competing nature of the interactions between the solutes and water. Finally, the intensity of the phase-forming ability in the [C 4 mim]X (X = Cl − or Br − ) + salt ATPS’s was also examined on the basis of the ionic viscosity B -coefficients of the Jones−Dole equation.