The physicochemical and thermodynamic properties of the choline chloride-based deep eutectic solvents

Abstract

This paper reports the physicochemical (density, dynamic viscosity, electrical conductivity and refractive index) and the thermodynamic (thermal expansion coefficient, molecular volume, lattice energy and heat capacity) properties of several choline chloride (ChCl) based deep eutectic solvents (DESs), with 1:2 mole ratio, respectively: ChCl:propylene glycol, ChCl:1,3-dimethylurea and ChCl:thiourea, at atmospheric pressure as a function of temperature over the range of 293.15?363.15 K. Their properties were also compared with those of some already characterized ChCl-based DESs, namely ChCl:ethylene glycol, ChCl:glycerol and ChCl:urea (1:2 mole ratio). Density, viscosity and refractive index of all DESs decrease with the increasing temperature while the electrical conductivity increases. Viscosity and conductivity of the tested DESs were fitted by both Arrhenius-type and Vogel?Tamman?Fulcher equations. The changes of molar enthalpy, entropy and Gibbs energy of activation, determined using the Eyring theory, demonstrated the interactional factor as predominant over the structural factor for all DES systems. The fractional Walden rule, used to correlate molar conductivity and viscosity, showed an excellent linear behaviour. It was shown that ChCl:propylene glycol DES had properties similar to ChCl:ethylene glycol and ChCl:glycerol DESs. However, the properties (density, viscosity and electrical conductivity) of ChCl:1,3-dimethylurea and ChCl: :thiourea DESs were inferior to those of the ChCl:urea DES. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45001]

Reduction of the Coefficient of Friction of Steel-Steel Tribological Contacts by Novel Graphene-Deep Eutectic Solvents (DESs) Lubricants

“…Values of physical properties including viscosity, conductivity, density and surface tension have been taken from similar works reported previously in the literature. Table 1 shows the physical properties of the DES used in present study [11,[27][28][29]. As can be seen, viscosity of ChCl-urea > EG > ChCl-malic, which can be attributed to the formation of stronger hydrogen bonds in deep eutectic solvents (DESs) with urea-based compounds.…”

Purification of motor fuels by means of extraction using deep eutectic solvent based on choline chloride and glycerol

“…The refractive index of ChCl-Gly 1:2 at 25 ∘ C amounts to 1.4838 which is similar to 1.48675 as reported by Leron et al 37 On the other hand, Troter et al published values for ChCl-Gly 1:2 higher than 1.48. 38…”

The extraction of quercetin from waste onion (Allium cepa L.): Tunic by the aqueous solutions of different deep eutectic solvents

“…The properties of the prepared DESs at room temperature are given in Table 1. The physical and thermodynamic properties of the ChCland citric acid-based DESs can be found elsewhere [6,20].…”

“…In recent years, deep eutectic solvents (DESs) have been used in different extraction processes. DESs are usually prepared by combining organic halide salts with a complexing organic agent (usually a hydrogen bond donor) in proper ratios, and are liquid at temperatures below 100 °C [6]. Beneficial properties of DESs are easy preparation, high purity, low cost, non-volatility at ambient condition, chemical and thermal stability, non-flammability, non-toxicity, biodegradability and good solubility of several organic compounds [7][8].…”