Liquid–liquid equilibria for 1-butyl-4-methylpyridinium tetrafluoroborate and inorganic salts aqueous two-phase systems

Abstract

Liquid–liquid equilibria were determined at 305.15 K for aqueous two-phase systems (ATPSs) containing 1-butyl-4-methylpyridinium tetrafluoroborate + inorganic salts (NaH2PO4·2H2O, (NH4)2SO4, Na2SO4, and Na2HPO4·12H2O) + water. Four nonlinear equations were used to correlate the binodal data, and the binodal curves were used to describe and display the effect of different experimental salts on phase separation. Furthermore, a simple, two-parameter equation, along with the Othmer–Tobias and Bancroft equations, was used to correlate the tie-line data. All the results showed good agreement between the fitting equations and the experimental data. The effect of temperature on the binodal curves and tie-lines for 1-butyl-4-methylpyridinium tetrafluoroborate + Na2SO4 + water systems was studied at T = 298.15, 311.15 and 338.15 K. Additionally, the effect of Gibbs energy on the salting-out ability of the different inorganic salts was discussed. From this study, we concluded that these salting-out abilities decline in the following order: Na2HPO4 > Na2SO4 > (NH4)2SO4 > NaH2PO4. These data may be helpful for the further investigation of ATPSs based on the ionic liquid 1-butyl-4-methylpyridinium tetrafluoroborate. In summary, our study determined the basic extraction data for this aqueous two-phase system and developed a fundamental method for the further study of material separation.