Effect of Ionic Liquids on the Solubility of Lithium Bromide in Aqueous Solution: Experimental Measurement and Prediction

The paper presents experimentally determined solubility results of lithium bromide in ionic liquid + water and assesses the effect of the addition of ionic liquids (ILs) on the solubility of lithium bromide (LiBr) in water. The solubility of LiBr in pure water has been determined and compared to the literature data. It is known that LiBr aqueous solutions are widely used as working fluids in low-temperature thermal energy recovery systems. However, the aqueous LiBr solution is easy to crystallize, which could cause equipment corrosion. One of the possibilities for improving the properties of the H₂O/LiBr refrigerant system is the use of an additive to increase the solubility of LiBr in water. Three ILs were selected as an additive: 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), 1-ethyl-3-methylimidazolium bromide ([EMIM]Br), and 1-butyl-3-methylimidazolium bromide ([BMIM]Br). In this study, new empirical parameters for the calculation of LiBr solubility in water were provided. A reasonable prediction of phase equilibrium data is made using the COSMO-SAC model. The NRTL equation is also calculated. The maximum deviation of COSMO-SAC is 7.56%, and the deviation of the other calculations is less than 2%. These experimental and theoretical findings offer valuable insights into the selection and optimization of working fluids in absorption cycle systems.