Phase Diagrams for Aqueous Two-Phase Systems Containing the 1-Ethyl-3-methylimidazolium Tetrafluoroborate/1-Propyl-3-methylimidazolium Tetrafluoroborate and Trisodium Phosphate/Sodium Sulfite/Sodium Dihydrogen Phosphate at 298.15 K: Experiment and Correlation

Liquid-liquid equilibrium data have been determined for 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emin]BF4)/1-propyl-3-methylimidazolium tetrafluoroborate ([Pmim]BF4) + trisodium phosphate (Na3PO4)/sodium sulfite (Na2SO3)/sodium dihydrogen phosphate (NaH2PO4) aqueous two-phase systems at T = 298.15 K, respectively. Two empirical equations were used to correlate binodal data. The Othmer-Tobias and Bancroft as well as Setschenow-type equations were used to correlate the tie-line data. The results show that good agreement was obtained with the experimental data. The effect of salt on the phase forming ability has been studied based on the effective excluded volume (REV) values from fitting the binodal data to the binodal model. The binodal curves and EEV both indicate that the salting-out effect of the three salts follow the order Na3PO4 > Na2SO3 > NaH2PO4, which can also be related to the Gibbs free energy of hydration of the ions (Delta(hyd)G) and [Pmim]BF4 is easier to be excluded the IL-rich phase than [Emim]BF4.