Influence of the addition of Tween 20 on the phase behaviour of ionic liquids-based aqueous systems

• Tween 20 in aqueous solutions of sulfate-based ionic liquids was investigated.
• Salting-out capacity of potassium-based salts in aqueous solutions of ionic liquids.
• Several empirical correlation equations are able to map solubility curves.

The addition of a non-ionic surfactant (Tween 20) to 1-ethyl-3methyl imidazolium alkylsulfate (C2C1imCnSO4)-based aqueous biphasic systems was investigated in this work. The solubility curves of the systems {(C2C1imCnSO4 (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 (ΔhydG) 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.