Single-step integrated CO2 absorption and mineralization using fly ash coupled mixed amine solution: Mineralization performance and reaction kinetics

Single-step integrated CO2 absorption and mineralization (IAM) using fly ash and mixed amine can reduce high energy consumption of absorbent regeneration while enabling the treatment of solid waste, however, the mineralization performance and kinetics are still unclear. This study adopted monoethanolamine (MEA)/N-Methyldiethanolamine (MDEA) mixed amine solution (MAS) as CO2 absorbent and fly ash as mineralizing materials to complete the IAM process in single-step, while realizing the regeneration of mixed amine. The mineralization performance was studied, and the reaction kinetics were analyzed by surface coverage model. The results demonstrated that fly ash effectively mineralized the absorbed CO2 in MAS and mixed amine regenerated. The mineralization efficiency reached maximum of 64.8 % at 40 °C, solid-liquid (S/L) ratio of 100 g/L, stirring rate of 500 r/min and 90 min, reaching 60.3 % after 10 cycles. The kinetic results demonstrated that surface coverage model exhibited excellent predictive capability for mineralization process (correlation coefficient (R2) > 0.99), with identification of surface reaction governed by calcium leaching as the primary rate-limiting factor. The regeneration of mixed amine was achieved by forming carbamate and protonated amine. The CO32−/HCO3− effectively reacted with the active Ca2+ ions in fly ash to realize mineralization, and the mineralization solid products was mainly CaCO3.