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Pure Appl. Chem., 2008, Vol. 80, No. 6, pp. 1325-1335

Ternary mixtures of phosphonium ionic liquids + organic solvents + water

Shahana A. Chowdhury1, Janet L. Scott1 and Douglas R. MacFarlane2

1 ARC Special Research Centre for Green Chemistry, Monash University, Clayton, Victoria 3800, Australia
2 School of Chemistry, Monash University, Clayton, Victoria 3800, Australia

Abstract: Ionic liquids (ILs) and water are both potentially green solvents that are useful in a variety of extraction processes. This report presents the ternary phase diagrams and tie-line data of trihexyl(tetradecyl)phosphonium dicyanamide [P6,6,6,14][DCA], phosphonium bis(2,4,4-trimethylpentyl)phosphinate [P6,6,6,14][((CH3)3C5H8)2PO2], and 1-ethyl-3-methylimidazolium ethylsulfate [emim][C2H5SO4] ILs in organic solvents (ethanol, acetonitrile, toluene) and water. [P6,6,6,14][DCA] and [P6,6,6,14][((CH3)3C5H8)2PO2] tended to yield emulsions when combined with water and ethanol, while [emim][C2H5SO4] combined with toluene and water provided two clear phases of reasonable viscosity. The compositions of the ternary mixtures were determined to obtain the tie-lines. A noticeable difference was observed for the tie-lines of the same IL (e.g., [P6,6,6,14][DCA]) with different organic solvents (ethanol and acetonitrile) and water mixtures. In all cases, the addition of ethanol eventually produced a single phase.