Phase behavior for 1-butyl-3-methylimidazolium tetrafluoroborate with sodium oxalate/succinate/formate aqueous two-phase systems at 298.15 and 308.15 K

Abstract

The liquid––liquid equilibrium (LLE) data and phase composition of the aqueous 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF₄) + sodium oxalate (Na₂C₂O₄), [Bmim]BF₄ + sodium succinate (Na₂C₄H₄O₄) and [Bmim]BF₄ + sodium formate (NaHCOO) mixtures have been measured at 298.15 and 308.15 K. The effect of salts and temperature on binodal curves were studied in this work and a significant relationship has been observed between the salting-out ability and the Gibbs energy of hydration of the ions. The binodal data obtained were correlated by the Pirdashti and Merchuk equations and the tie-line compositions were well-fitted by the Othmer-Tobias and Bancroft equations and the experimental tie-line data were well correlated with extended UNIQUAC model. Additionally, the effective excluded volume values were also determined to analyze the salting-out abilities of the three salts which follow the order of Na₂C₂O₄ > Na₂C₄H₄O₄ > NaHCOO.

Graphical Abstract

Keywords:

• Aqueous two-phase systems
• ionic liquid
• temperature
• anion
• ionic strength