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

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.