[1-Ethyl-3-Methyl-Imidazolium][EthylSulfate]-based aqueous two phase systems: New experimental data and new modelling

• A new class of ATPS of [emim][eSO4] and salts at various temperature are introduced.
• Ability of salts on extraction of IL-based ATPS versus temperature are investigated.
• The cation of salt presents the major effect on the phase forming of the ATPS.
• A new model based on a symmetrical reference state is applied.
• The model consisting of PDH and NRTL-NRF models.

Ionic liquids (ILs), a class of organic salts comprising entirely of ions, are considered as a novel replacement for many traditional organic compounds. Among the various ILs, the alkyl-sulfate derivatives have the great advantages such as synthesizing easily in a halide-free way at a reasonable cost with relatively low viscosity and considering as a promising IL in aqueous two-phase systems (ATPSs). In this work, a new ATPS is introduced through the aqueous salt–IL solution. The effect of various inorganic salts such as K2HPO4, Na2SO4 and Na2CO3 are investigated on the phase separation of [1-Ethyl-3-Methyl-Imidazolium][Ethyl-Sulfate] ([emim][eSO4])-based ATPSs at T = (288.15, 298.15, and 313.15) K. The results showed that the ability of phase separation of the salt–IL based ATPS follows the order Na2CO3 > Na2SO4 > K2HPO4. The experimental results are correlated successfully using a new model comprising the symmetrical Pitzer–Debye–Hückel (PDH) equation as a long-range contribution and non-random two liquid non-random factor (NRTL-NRF) equation as a short-range contribution. The new model is applied successfully to correlate the aqueous two-phase systems of {[1-Ethyl-3-Methyl-Imidazolium][Ethyl-Sulfate] ([emim][eSO4])} + salt solutions.