Experimental investigation and modeling of thermophysical and extraction properties of choline chloride + DL-malic acid based deep eutectic solvent

The ability of non-toxic and biodegradable deep eutectic solvent (DES) choline chloride + DL-malic acid in mole ratio 1:1, for the breaking of the azeotropes heptane + methanol and toluene + methanol by means of liquid––liquid extraction was evaluated. Ternary liquid–liquid equilibrium experi­ments were performed at 298.15 K and at atmospheric pressure. Densities, viscosities and refractive indices of DES + methanol and water + DES systems were experimentally determined over a wide temperature range and at atmo­spheric pressure. Additionally, the viscosities of DES + glycerol mixture were -determined at temperatures up to 363.15 K to check how much the addition of glycerol decreases high viscosities of DES. The results indicate that the addi­tion of small amounts of water or glycerol as a third component significantly decreases the viscosity of the investigated deep eutectic solvent. Based on the selectivity and distribution ratio values, the extraction ability of the inves­tigated deep eutectic solvent, in comparison with the conventionally used sol­vents, yields promising results. Non-random two-liquid (NRTL) and universal quasichemical (UNIQUAC) models were satisfactorily applied for correlation of experimental phase equilibrium data for two ternary mixtures.