Phase diagrams of aqueous biphasic systems composed of ionic liquids and dipotassium carbonate at different temperatures

•The phase diagrams for the ILs + K2CO3 aqueous biphasic systems were measured.•The binodal curves for the IL + K2CO3 aqueous biphasic systems were determined.•The effect of temperature on two phase formation was studied.•The ionic liquids [Bmim][NO3], [Hmim][NO3] and [Omim][NO3] were used.•The NRTL model was used for correlation of the experimental tie line data.

Phase diagrams of the {1-butyl-3-methylimidazolium nitrate ([Bmim][NO3])/1-hexyl-3-methylimidazolium nitrate ([Hmim][NO3]) + dipotassium carbonate (K2CO3)} aqueous biphasic systems (ABS) and the binodal curves of {1-octyl-3-methylimidazolium nitrate ([Omim][NO3]) + K2CO3} ABS were determined experimentally at different temperatures. The binodal data were correlated with the Merchuk equation. The effect of temperature and the alkyl chain length of ionic liquid (IL) on two phase formation were investigated. The experimental data reveals the biphasic region expands with reduction in temperature; however, the absolute value of slope of the tie-lines reduces with an increase in temperature. Moreover, the ability of the studied ILs to form two phase in the presence of K2CO3 salt are in the order of [Hmim][NO3] > [Omim][NO3] > [Bmim][NO3]. The experimental data are correlated with the NRTL model with a good accuracy.