In this work, a new type of ionic-liquid-based aqueous two phase systems namely [1-ethyl-2,3dimethylimidazolium][ethylsulfate] ([emmim][eSO(4)]))-salt is introduced and investigated. Effect of various inorganic salts Na2CO3, Na2SO4 and K2HPO4 on the phase forming ability of [emmim][eSO(4)] 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][eSO(4)]-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-Huckel (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. (C) 2014 Elsevier B.V. All rights reserved.