Experimental and theoretical assessing the salts effect on the equilibrium of water + acetone + HMIMPF6 ionic liquid system

• Effects of conventional salts on the LLE of water + acetone + HMIMPF6 ionic liquid were examined.
• The binodal curves were determined by cloud point measurement method.
• Presence of salts gives high enhancements in separation of acetone from aqueous phase.
• The consistency of LLE tie-lines were assessed with the improved Eisen-Joffe equation.
• The NRTL and UNIQUAC models were applied satisfactorily to correlate the equilibrium data.

The influence of naturally occurring monovalent NaCl and divalent Na2SO4 salts with anions at near extremes of Hafmester series on liquid–liquid equilibrium (LLE) of the chemical system of {water + acetone + 1-Hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF6) ionic liquid} was studied. The conditions were 298.2 K, atmospheric pressure of 81.5 kPa and salts mass fractions in initial aqueous solutions of 0.05 and 0.10. Results show that salting-out effect was significant, so that enhancements in the acetone distribution coefficient was achieved within (21.67–35.54)% for NaCl and (51.84–92.37)% for Na2SO4. The stronger anion activity and the lack of anion exchange with the used ionic liquid can be the reasons for the stronger effect of the latter salt. The consistency of the experimental data were examined with the improved Eisen-Joffe equation. For modeling purpose, the NRTL and UNIQUAC equations were satisfactorily applied to correlate the phase equilibria. In the presence of NaCl and Na2SO4 salts, the root mean square deviations of compositions, for NRTL equation were 0.0346 and 0.0634 and for UNIQUAC equation 0.1093 and 0.0328, respectively.

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