Experimental investigation and thermodynamic modeling of the CO2 capturing in an aqueous choline chloride + 2-(2-aminoethylamino) ethanol-based deep eutectic solvent

Abstract

Since their initial discovery, deep eutectic solvents (DESs) have garnered significant attention and demonstrated versatility in various applications, particularly in gas solubility research. This study examines a novel aqueous amine-based DES, formulated from choline chloride, 2-(2-aminoethylamino)ethanol, and water, in molar ratios of 1:2 and 1:3, with water contents of 50 % and 70 % (wt./wt.), to evaluate its CO₂ solubility potential. CO₂ solubility measurements were performed in a quasi-static high-pressure equilibrium cell at temperatures of 313.15, 328.15, and 343.15 K, with pressures up to 50 bar. The results indicate that increased water content leads to decreased CO₂ solubility, likely due to a reduction in available active sites as hydrogen bonds within the DES structure are disrupted. To model the solubility data, we applied the Peng-Robinson equation of state using the φ-φ approach, and the Non-Random Two-Liquid (NRTL) model paired with the Redlich-Kwong (RK) equation of state by the γ-φ algorithm. Both frameworks demonstrated a strong correlation of the experimental data, with the experimental and predicted values aligning closely. The maximum average absolute relative deviations (AARD) were 5.51 % for the NRTL-RK modeling and 8.57 % for the Peng-Robinson model. The lower deviation observed with the NRTL-RK model suggests a superior capacity to capture the highly non-ideal behavior of the DES, where hydrogen bonding significantly influences the solvent’s thermodynamic properties, especially at elevated pressures.