Abstract

One of the environmental concerns in the chemical industry is using organic solvents that are not environmentally friendly. Eutectic mixtures, also called deep eutectic solvents (DESs), have emerged as their substitutes due to favorable properties, including biodegradability, tunability, and low cost, among others. DESs show applications in extractions, biocatalysis, etc. To expand their uses, it is crucial to characterize their properties and understand their interactions with other solvents. In this study, the surface tension of DESs between 30 and 60 degrees C at 101.3 kPa was measured. The DESs were prepared using choline chloride or betaine as the hydrogen bond acceptor (HBA) and a glycol (ethylene glycol, 1,2-propanediol, 1,3-propanediol, or 1,4-butanediol) as the hydrogen bond donor (HBD) in different molar ratios. The surface tension of DESs + water mixtures was measured over the entire range of compositions. To assess the effect of temperature, HBD chain length, and water content, PC-SAFT coupled with the density gradient theory was used to model the surface tension. Furthermore, molecular dynamics simulations were conducted to gain a molecular understanding of the components at the interface. The molecular insights obtained from these simulations and the experimental data can help reduce the number of experiments when designing DESs for chemical processes.