[1-Ethyl-2,3-dimethyl-imidazolium][ethylsulfate]-based aqueous two phase systems: New experimental data and modeling

• Aqueous two phase partitioning system containing [emmim][eSO4] ionic liquid is introduced.
• Effect of salts and temperature on the phase forming of the IL–salt ATPSs are assessed.
• The salts have significant effect on the phase separation while the temperature effect is negligible.
• A symmetrical activity coefficient model comprising of PDH and Wilson-NRF equations is applied.
• The model successfully correlated all the data with an overall ARD of 0.0710.

In this work, a new type of ionic-liquid-based aqueous two phase systems namely [1-ethyl-2,3-dimethylimidazolium][ethylsulfate] ([emmim][eSO4])–salt is introduced and investigated. Effect of various inorganic salts Na2CO3, Na2SO4 and K2HPO4 on the phase forming ability of [emmim][eSO4] at different temperature (T/K = 288.15, 298.15 and 313.15) are assessed. The results indicate that the effect of temperature in comparison with salt effect is negligible and the ability of the salts to phase separation of the [emmim][eSO4]-based aqueous two phase systems, follows the order Na2CO3 ≥ Na2SO4 > K2HPO4. Moreover, the experimental data are successfully correlated using a new thermodynamic model based on symmetrical activity coefficient model with an overall average relative deviation (ARD) of 0.0710. In this model, the long-range contribution is accounted by Pitzer–Debye–Hückel (PDH) equation while the short-range contribution is considered by nonelectrolyte Wilson non-randomness-factor (Wilson-NRF) model. The result of the correlation shows that the applied model could successfully correlate the phase behavior of the ionic liquid-based aqueous two phase systems.

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