Experimental and theoretical excess molar properties of aqueous choline chloride based deep eutectic solvents

Abstract

Deep eutectic solvents (DESs), an alternative to ionic liquids and conventional molecular organic solvents have attracted scientific attention because of their unique physico-chemical properties that can be tuned judiciously. These physico-chemical properties are altered if water, the most eco-friendly solvent is present as an impurity or as a cosolvent. The peculiar effect of water on the thermodynamic properties of DESs composed of choline chloride (CH) as an hydrogen bond acceptor (HBA) and ethylene glycol (EG), glycerol (GLY) and 1,4-butanediol (BD) as hydrogen bond donors (HBD) in the ratio of 1:2 are reported here. Densities of the aqueous solutions of CH:EG, CH:GLY and CH:BD were measured over the entire range of composition and temperature ranges from 293.15 K to 323.15 K at atmospheric pressure. Intermolecular interactions responsible for the negative excess molar volumes VmE for all the mixtures studied have been discussed. The non-ideal behavior of the studied mixtures have been evaluated through comparing the values of VmE with the Prigogine−Flory−Patterson (PFP) theory and extended real associated solution model (ERAS). These results will be further utilized in industrial processes as well as in the thermodynamic modeling of DES based systems.