Binary mixtures of HMIMPF₆ ionic liquid and n-butyl acetate cosolvent in the extraction of acetone from aqueous solutions

ABSTRACT

A remarkable disadvantage of pure ionic liquids, to be used as a solvent in different processes, is their high viscosity and density. Here, n-butyl acetate was used as a cosolvent in the liquid–liquid system of {water + acetone + 1-hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF₆) ionic liquid}. Mixtures of the ionic liquid and the cosolvent were used as the organic phase to extract acetone from aqueous phase. A drastic decrease in viscosity and a significant decrease in density of the ionic liquid were achieved in the presence of cosolvent. Accordingly, the liquid–liquid equilibrium of different provided systems was studied under temperature of 298.2 K and atmospheric pressure of 81.5 kPa. Binary phase regions and corresponding tie-lines and binodal curves were obtained for ternary and quaternary systems. Results show the extension of the binodal solubility region as well as enhancements up to 41.8% in the acetone separation factor. The tie-line data consistency was confirmed by the Othmer–Tobias and the Hand equations. Moreover, the nonrandom two-liquid model of activity coefficient was applied satisfactorily to reproduce the equilibrium data with a root-mean-square deviation of only 1.95%.

KEYWORDS:

• Cosolvent
• extraction
• ionic liquids
• liquid–liquid equilibrium
• NRTL model
• physical properties

Acknowledgment

The Bu-Ali Sina University authorities are acknowledged. Prof. A. Pfennig and M. Quaresima at University of Liege, Belgium, are also acknowledged for their useful advice and performing the viscosity measurements.

Additional information

Funding

The authors wish to acknowledge Iran National Science Foundation (INSF) for financial support of this work.