Phase segregation in aqueous solutions of non-ionic surfactants using ammonium, magnesium and iron salts

• Ammonium, iron and magnesium salts were selected as efficient salting-out agents.
• Immiscibility regions were mapped together with the tie-lines.
• Suitable correlation models were employed to describe the solubility data.
• Phase segregation was investigated in terms of several thermodynamic parameters.

Aqueous Biphasic Systems (ABS) are suggested as a separation technique for a great diversity of compounds, making it necessary to characterise fully the solubility data of these kinds of systems. In this study, the non-ionic surfactants Tween 20 and Triton X-100 are proposed as candidates to form ABS, with different inorganic and organic salts ((NH4)2Fe(SO4)2, MgSO4, (NH4)2HPO4, (NH4)2SO4, (NH4)2C4H4O6) at T = 298.15 K. All the solubility data were obtained by means of the cloud point method and the salting-out ability of salts was also evaluated in terms of the Gibbs free energy of hydration (ΔhydG) and molar entropy of hydration (ΔhydS). The Merchuk equation and some variations of this model have been used for correlating the solubility curve. The extraction capacity k was evaluated in terms of tie-lines (TL) data.