Absorption-mineralization performance and reaction mechanism of an amino acid salt-based blended amine for CO2 capture

The integrated absorption-mineralization (IAM) technology enables mild regeneration of the absorbent and permanent CO 2 storage in CO 2 capture systems. However, developing green and efficient absorbents remains the core challenge for this technology. In this study, potassium lysinate (LysK) was used as the main amine, and systematic investigations were carried out, including optimal formulation screening, mineralization process optimization, reaction mechanism analysis, and cyclic stability evaluation. The results showed that 2-amino-2-methyl-1-propanol (AMP) was the optimal auxiliary amine. The blended amine composed of 1.6 mol/L LysK and 0.4 mol/L AMP achieved a mineralization rate 15.28 percentage points higher than that of pure LysK, while maintaining a high CO 2 absorption capacity of 1.17 mol CO 2 /mol absorbent. Under optimal mineralization conditions, the mineralization rate reached 99.56%, approaching the theoretical maximum. The Ca 2+ /CO 2 molar ratio and stirring speed only regulated the mineralization kinetics without altering the final thermodynamic equilibrium state. The mineralization priority of different CO 2 species in the system followed: free HCO 3 − /CO 3 2−  > ε-carbamate > α-carbamate. The mineralization product was predominantly high-purity calcite calcium carbonate, which meets the requirements for permanent storage. After ten absorption-mineralization cycles, the mineralization capacity and pH of the system remained stable, with no obvious performance degradation. The physical entrainment loss of the absorbent was quantitatively determined to be approximately 0.155 mmol/g CaCO 3 per cycle. A preliminary economic assessment shows that after deducting the direct operating costs, the co-production of precipitated calcium carbonate yields a gross profit of approximately 677.4 USD/t CO 2 (4567.2 CNY/t CO₂), indicating that the system possesses value-adding potential. The LysK-AMP blended amine system developed in this study combines high capture efficiency, low regeneration energy consumption, and excellent cyclic stability, providing a theoretical basis and experimental verification for the industrial application of IAM technology.