Liquid–Liquid Equilibrium and Extraction Performance of Aqueous Biphasic Systems Composed of Water, Cholinium Carboxylate Ionic Liquids and K2CO3

Abstract

Ionic-liquid-based aqueous biphasic systems (IL-based ABS) have been broadly investigated for the separation of high-value compounds. Nevertheless, the large-scale application of IL-based ABS is still hampered by the high cost and hazardous features of most ILs used. Aiming at characterizing novel ABS composed of ILs with a more acceptable environmental footprint and enhanced biocompatibility, in this work, ABS formed by water, cholinium carboxylate ILs ([Ch][CnCO2], with n = 2 to 6), and K2CO3 were investigated. The respective ternary phase diagrams, including binodal curves, tie-lines, and critical points, were determined at (298 ± 1) K and atmospheric pressure. The capability to form ABS (or of the IL to be salted-out) increased with the increase of the alkyl chain length of the IL anion up to cholinium pentanoate; however, for longer anion alkyl chain lengths the ILs self-aggregation led to a decrease of the ILs ability to form ABS. Furthermore, the liquid–liquid equilibrium data experimentally determ...