The study of aqueous
two-phase systems (ATPSs) formed by ionic
liquids based on the choline cation and nonionic surfactants has received
attention in recent years because of the biodegradability and nontoxicity
of their components. In this work, liquid–liquid equilibrium
data were obtained for ATPSs composed of Triton X (Triton X-100, Triton
X-165, and Triton X-305), choline chloride, and water, at 298.15,
313.15, and 328.15 K. In general, these systems presented a top phase
rich in choline chloride and a bottom phase rich in surfactant, although
the phenomenon of phase inversion was observed for a specific thermodynamic
condition of the system formed by Triton X-165. It was observed that
increase of the temperature led to an increase of the biphasic region,
indicating an endothermic phase separation process. In addition, higher
hydrophobicity of the surfactant increased its ability to promote
phase segregation (the biphasic region increased in the following
order: Triton X-100 > Triton X-165 > Triton X-305). The reliability
of the equilibrium data was confirmed using the Othmer–Tobias
and Bancroft correlations.