Dissolution and separation of carbon dioxide in biohydrogen by monoethanolamine‐based deep eutectic solvents

Abstract Background The presence of CO 2 in biohydrogen reduces hydrogen purity, thereby limiting its application in fuel cells, hydrogen‐enriched water and other advanced energy sectors. To improve biohydrogen purity, the solubility of pure CO 2 under different molar ratios, temperatures and aqueous deep eutectic solvents (DESs) concentrations were studied, and a response surface optimization experiment was carried out. Subsequently, aqueous DESs were utilized to investigate the decarbonization and purification of biohydrogen at varying temperatures and biohydrogen flow rates. Results The results demonstrated that the DESs composed of acetamide and monoethanolamine (A‐MEA) exhibited effective CO 2 solubility properties at 65 °C. Upon the addition of water, the viscosity of A‐MEA was significantly reduced, improving its fluidity. Notably, the optimum CO 2 dissolution temperature of aqueous A‐MEA decreased to 40 °C. Optimal purification performance was achieved when biohydrogen was passed through 40% aqueous A‐MEA at a flow rate of 100 mL min −1 . Under these conditions, hydrogen purity increased from 60.00% to over 99.00% and was sustained for 21 min. Simultaneously, the CO 2 ‐dissolving capacity of the solvent reached 0.311 g CO 2 g −1 A‐MEA. Conclusion Aqueous A‐MEA is an efficient CO 2 absorbent that provides important insights for advancing biohydrogen purification and laying the foundation for its future industrial‐scale application. © 2025 Society of Chemical Industry (SCI).