Exploring the Physicochemical Properties and PC-SAFT Modeling of a Mixture of Deep Eutectic Solvent (Choline Chloride and Butyric Acid) + Water

Abstract

This study reports measurement of density (ρ), speed of sound (u), and dynamic viscosity (η) of a choline chloride and butyric acid deep eutectic solvent (ChCl/BA DES) and investigates its physicochemical properties and its aqueous mixtures for the entire range of composition at T = 303.15−343.15 K. The density data are fitted by the second-degree polynomial equation in T, and the fourth-degree polynomial equation in the mole fraction of ChCl/BA DES (x1) is fitted well for both ρ and η. Excess molar volume (VE ) shows a positive deviation from ideality with the minimum centered at x1 ≈ 0.5. Viscosity deviation (Δη) exhibits a minimum at x1 ≈ 0.5, aligning with VE behavior and confirming mixture stability. Isentropic compressibility deviation (ΔκS) shows a negative deviation with a minimum at x1 ≈ 0.15. Excess properties (VE

, ΔκS and Δη) are correlated by the Redlich− Kister (R−K) polynomial equation. The molar volume (V), lattice energy (Upot), molar entropy (S0

), and intermolecular free length (Lf

) are evaluated to understand the derived thermodynamic properties. Temperature dependence of η is compared using Vogel−Fulcher−Tammann (VFT) and Arrhenius equations. The PC-SAFT equation of state quantitatively predicts ρ and VE of a pseudo-binary mixture composed of a DES and water with improved accuracy using the fitted approach.