Measurement and correlation of thermophysical properties in aqueous solutions of some novel bio-based deep eutectic solvents (lactic acid/amino acids) at T = (298.15 to 313.15) K

Abstract

Thermodynamic properties of novel bio-based deep eutectic solvents (DESs) and their mixture with other solvents is of great importance in extraction and pharmaceutical sciences. In the present study new class of these neoteric sustainable solvents composed of amino acids and lactic acid have been prepared, density and speed of sound data for neat lactic acid/alanine, lactic acid/glycine and lactic acid/histidine and their aqueous mixture have been measured over the entire composition range at T = (298.15, 303.15, 308.15 and 313.15) K. Based on these data, some of the thermodynamic properties including the excess molar volumes (VE), apparent molar volume (Vϕ), excess isobaric thermal expansion (αp,mE), the excess molar isentropic compressibility (κEs,m) and limiting apparent molar expansibility (ϕE,10) have been calculated. For all of the studied systems above, these important properties have been analysed based on various solute-solvent interactions, occurring between the components of the mixtures. Furthermore, it has been found that all the investigated DESs act as a structure-breaker in water over the whole temperature range using Hepler’s constant. The properties have been correlated by the Redlich-Kister type equations.