Phase equilibrium and ionic liquid partitioning in aqueous two-phase system composed of alcohol and small molecule compound

In this study, liquid–liquid equilibrium data of an aqueous two-phase system (ATPS) composed of alcohols (ethanol, 1-propanol, or 2-propanol) and small-molecule organic compound (sodium citrate, sodium tartrate, sucrose, maltose, and lactose) was extensively investigated at 298.1 K ± 0.1 K. The binodal curves were summarized through the empirical nonlinear equations with the lowest standard deviation. The contents of alcohols and organic salts in ATPS were accurately determined by gas chromatography and ultraviolet spectrophotometer. The phase-forming abilities of alcohols were ranked in the following order, 1-propanol > 2-propanol > ethanol, respectively. The ATPS composed of saccharides was difficult to form two phases due to the high viscosity. The salting-out abilities of sodium citrate (C6H5Na3O7) were better than sodium tartrate. 1-propanol/ C6H5Na3O7 ATPS had larger biphase areas, it was further applied to concentrate various ionic liquids including [C2mim]BF4, [C4mim]BF4, [C4mim]Cl and [C8mim]Cl. The results showed that alcohol/organic salt ATPS had a better extraction rate to imidazole-type ionic liquids. Ionic liquids were mainly distributed in the top phase (alcohol-rich phase).