Some thermodynamic properties and computational study of DESs (choline chloride/ethylene glycol and choline chloride/malonic acid) in lithium nitrate + propylene carbonate solutions at T = 298.15 K

Abstract

Deep eutectic solvents (DESs) with propylene carbonate represent an appealing alternative for organic solvents and ionic liquids to dissolve lithium salts. The present research reports the effect of deep eutectic solvents {DESs (choline chloride/ethylene glycol with the molar ratio of 1.00:2.00) and (choline chloride/malonic acid with the molar ratio of 1.00:1.00) on the thermodynamic and transport properties of solutions of lithium nitrate (LiNO3) in propylene carbonate (PC). To evaluate solute–solvent interactions in the above systems first the volumetric, ultrasonic, and viscometric properties were studied. For this purpose, the density (d), speed of sound (C) and viscosity (η) were measured for the binary solutions of (LiNO3 + PC) and quaternary solutions containing (LiNO3 + PC) and DES in different mass fraction of, w = (0.05, 0.010, 0.015 and 0.020), at 298.15 K under ambient pressure. The measured data were used for calculation of the apparent molar volume (Vφ), standard partial molar volume (Vφ0), apparent molar isentropic compressibility (κϕ), partial molar isentropic compressibility (κφ0), partial molar volumes of transfer (ΔtrVφ0) and viscosity B-coefficient of (LiNO3 + PC + DES) solutions. Then, to evaluate the interaction energies, the density functional theory (DFT) of LiNO3 with DESs in PC has also been studied. The thermodynamic and transport investigations indicated that the choline chloride/ethylene glycol interactions are more favorable than choline chloride/malonic acid with LiNO3 in the presence of PC. Generally, the additions of these DESs on the solution of LiNO3 + PC lead to enhancing of the solute–solvent interactions. Also, the DFT results revealed that the interaction between the ChCl/EG with LiNO3 in PC is stronger than ChCl/MA with LiNO3 in PC confirming the result deduced from our experimental studies.