Physicochemical Properties of N,N-Diethylethanolammonium Chloride/Ethylene Glycol-Based Deep Eutectic Solvent for Replacement of Ionic Liquid

Abstract

Ionic liquids (ILs) that are used in the market nowadays have high complexity of processing, high viscosity, and high toxicity in comparison to deep eutectic solvent (DES). Deep eutectic solvent is typically used in thermal energy storage, separation and extraction process or electrochemistry field. This study focuses on determining the physicochemical properties of DES, which are thermal conductivity, viscosity, and surface tension. DES was prepared by mixing hydrogen-bond donor (HBD) compounds (ethylene glycol) and hydrogen-bond acceptor (HBA) compounds (N,N-diethylethanolammonium chloride) at different molar compositions. The data show that the molar ratio HBA:HBD of 1:2 resulted in optimized values of thermal conductivity (0.218 W/mK), low viscosity (38.1 cP), and high surface tension (54 mN/m). Most notably, DES is capable of sustaining in a liquid phase at ambient condition (25 °C) for more than 30 days. Fourier transform infrared spectrum did not indicate any presence of a new peak. This established that only delocalization of ions occurred, and hence, chemical transformations did not take place during mixing. The data obtained showed that the newly synthesized solvent (DES) possess better result than the ILs. Therefore, DES can be proposed to replace the dependency on ILs.