Thermodynamic study of the aqueous pseudo-binary mixtures of betaine-based deep eutectic solvents at T = (293.15 to 313.15) K

ABSTRACT

This work investigates physicochemical properties of betaine/propylene glycol (Bet/PG) and betaine/ethylene glycol (Bet/EG) DESs in water by measuring their densities in neat state and aqueous mixtures over the entire composition range at T = (288.15–318.15) K under atmospheric pressure (≈ 85 kPa). The obtained values of density were used to compute the excess molar volumes ($V^E$), molar volume (V_m), apparent molar volume ($V_{\phi ,DES}$), limiting apparent molar expansibility (${\varphi }_{E,1}^0$) and the isobaric thermal expansion coefficient (${\alpha }_{p,m}$). The solute-solvent interactions in the investigated solutions are evaluated on the basis of these important physicochemical properties. The results indicated that two studied DESs act as a structure-making solute in water over the whole temperature range using Hepler’s constant. Finally, the experimental densities were correlated with some models including Jouyban-Acree, Jouyban-Acree-van’t Hoff, modified Jouyban-Acree-van’t Hoff, Redlich-Kister and Emmerling. The Redlich-Kister expression and Jouyban-Acree model were also used for representation of $V^E$ values.

KEYWORDS:

• Betaine-based deep eutectic solvents
• measurement and correlation of densities
• excess molar volumes
• solute-solvent interactions
• hepler’s constant

Acknowledgements

P. Jafari would like to thank a postdoctorate grant (64248) of Tabriz University of Medical Sciences (Iran) for supporting this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Tabriz University of Medical Sciences [64248].