The addition of a non-ionic surfactant (Tween 20) to 1-ethyl-3methyl imidazolium alkylsulfate (C(2)C(1)imC(n)SO(4))-based aqueous biphasic systems was investigated in this work. The solubility curves of the systems {(C(2)C(1)imC(n)SO(4) (n = 2 and 8) + Tween 20) + high charge density salt (K3PO4/K2CO3/K2HPO4) + H2O} were carried out at T = 298.15 K. The obtained experimental data were correlated by using three empirical equations. The molar Gibbs free energy of hydration (Delta(hyd)G) is a valuable parameter to analyse the segregation capacity provided by the inorganic salts. Additionally, the efficiency of the separation capacity was discussed in terms of the salting out potential of the selected salts and the presence of Tween 20. Othmer-Tobias and Bancroft equations have been used to correlate the experimental tie-line data. (C) 2014 Elsevier Ltd. All rights reserved.