Integrated CO₂ Capture and Mineralization Based on Monoethanolamine and Lime Kiln Dust

Development and deployment of innovative and cost-effective CO2 capture and utilization technologies can not only reduce the amount of CO2 currently in or being emitted into the atmosphere but also develop a circular economy and deliver economic growth. Differing from previous studies on amine-based CO2 capture in isolation, the work herein is focused on an integrated CO2 capture and mineralization approach with monoethanolamine (MEA) as CO2 liquid absorbent and utilization of lime kiln dust (LKD) as the CO2 mineralization feedstock to regenerate or recover MEA used for CO2 capture. Aqueous solutions containing 2.0 M MEA were used to capture CO2 from a simulated flue gas comprising a CO2 concentration of 10.0% (by volume) prior to the addition of LKD powders to precipitate captured CO2 in the MEA solution through carbonation reactions. Following CO2 mineralization, MEA filtrate was collected and analyzed by FTIR and ICP-OES, with solid materials undergoing chemical analysis by TGA and SEM, and additionally for particle size. The CO2 mineralization process was found to be significantly influenced by the solution pH and temperature of the MEA absorbent solution, where conditions below pH 10.5 restrained CO2 mineralization due to the limited availability of carbonate ions. Conversely, under higher pH conditions, the conversion of carbamate and bicarbonate to carbonate is promoted, accelerating the CO2 mineralization process. Increasing the absorbent temperature (i.e., from 40.0 to 60.0 °C) resulted in a corresponding and considerable increase in the CO2 mineralization rate and the CO2 desorption efficiency of MEA. Following mineralization, the CO2 desorption efficiency of CO2-loaded MEA reaches 79–83%. The CO2 sequestration capacity of LKD was determined to be ∼230 g CO2 per kg, with calcite and aragonite forms as the major calcium carbonate products formed during the CO2 mineralization processes.