Measurement and correlation of phase equilibria in aqueous two-phase systems containing functionalized magnetic ionic liquids and potassium phosphate at different temperatures

Functionalized magnetic ionic liquids ([C2TMG][TEMPO-OSO3], [C3TMG] [TEMPO-OSO3], [C4TMG][TEMPO-OSO3]) and K3PO4 were used as phase forming compounds of aqueous two-phase system at three temperatures (278.15 K, 298.15 K and 318.15 K). The effects of temperature and magnetic ionic liquid (MIL) species on the binodal curves were investigated. Three classical empirical equations were used for the correlations of the binodal curves. They have shown satisfactory performances in data fitting. An increase of the two-phase separation ability was observed when the temperature decreased. Additionally, all these three MILs have preferable phase forming ability as well as wide range of two-phase area in the binodal curve for our systems. This is strongly expected in practical applications. Furthermore, tie line data were experimentally acquired for the three MILs at 298.15 K. Three empirical formulas including Othmer-Tobias, Bancroft equations as well as an equation derived from binodal theory were used to fit the tie-line data with successful correlation. These aqueous two-phase equilibrium data should be useful in the areas of separation, purification and analysis.