Ionic liquids are organic salts with melting temperatures below 100°C. Their unique properties, such as a negligible vapor pressure, high chemical and thermal stabilities, wide liquidus temperature range, and the possibility of fine tuning their properties through appropriate cation/anion combinations make them viable candidates to replace the common organic and volatile solvents currently used in an extensive range of industrial applications. There are circa 600 organic solvents used by industry against the one million of possible combinations of ions or different ionic liquids. In particular, ionic liquids have been described as potential solvents for “clean” and tailored liquid-liquid extractions. Nevertheless, most of the liquid-liquid separation processes employing ionic liquids also require the use of a volatile molecular solvent. In this context, the search on novel biphasic liquid-liquid systems composed of two ionic liquids allows the creation of a new range of extraction systems constituted only by non-volatile solvents.<br/>The main goal of this work comprises the identification of ionic liquids pairs with limited solubility and that could lead to the development of novel liquid-liquid extraction processes. It was found that mixtures of cholinium- and phosphonium-based ionic liquids are not completely miscible in a wide range of temperatures. Their liquid-liquid phase diagrams were determined from (333.15 to 423.15) K by Nuclear Magnetic Resonance (NMR). Furthermore, the ions exchange amongst the two-phases was investigated since ionic liquids with non-common ions were used. It was found a significant ion exchange in the different systems, and that its extent closely correlates with the ionic liquids cation-anion interaction energies (determined in this work by Electrospray Ionization Mass Spectrometry).<br/>The novel biphasic mixtures investigated in this work expand the possibility of using two ionic liquids as non-volatile liquid-liquid systems in separation processes. Since both phases are composed of ionic liquids, they can be further tailored for a given separation process by adequately choosing their chemical structures.

Liquid-liquid equilibrium between two hydrophobic ionic liquids

254th National Meeting (2017)

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