Inspired by the lack of characterization of natural eutectic and deep eutectic (DES) systems, we studied the solid-liquid equilibria (SLE) of binary and ternary mixtures involving choline chloride and sugars. The densities, viscosities and solvatochromic parameters for the binary systems containing choline chloride, [Ch]Cl, were measured at the eutectic composition, and the water impact on these properties was also investigated in order to address the tailoring of their properties using water. Mixtures of sugars are shown to present an ideal behavior, while their binary mixtures with choline chloride present negative deviations to the ideality, particularly in the sugar solubility curve. Aiming to develop a predictive model to design new sugar based DES, the [Ch]Cl + sugars phase diagrams were used to tune the COnductor-like Screening MOdel for Real Solvents (COSMO-RS) parameters, which was after applied in the estimation of the eutectic points of new ternary DES. The predictions quality was checked experimentally, proving that COSMO-RS can be a useful tool for the design of deep eutectic solvents.

The potential of HESs as environmentally benign and tunable media for the solvent extraction of metal ions is presented.

Despite some promising potential applications of eutectic systems containing choline chloride and a polyalcohol, a detailed investigation of the thermodynamic behavior of these systems is still missing. In this work, the solid-liquid equilibria phase diagrams of binary systems containing choline chloride, and one from six different polyalcohols (ethylene glycol, 1,3-propanediol, glycerol, meso-erythritol, xylitol and sorbitol), were measured in the full composition. Excepting the mixtures with glycerol or ethylene glycol a quasi-ideal behavior in the [Ch]Cl solubility curve is observed. In the polyalcohol solubility curve, the mixtures present small negative deviations from ideality, excepting[Ch]Cl+ethylene glycol, which is slightly positive. The solid−liquid phase diagrams show a large liquidus composition window, and not a fixed stoichiometry for the eutectic points, where the mixtures can be used as solvents close, or below, room temperature. Aiming at their application, viscosities and densities were measured at the eutectic point in the temperature range from 278.15 to 373.15 K. All systems present densities and viscosities higher than water, which are directly related to the strong interactions between the components. Solvatochromic parameters were measured to characterize the solvents and they show how to achieve solvent tunability by varying the polyalcohol mole fraction.