Integrated CO₂ Capture and Mineralization Process Using Ionic Liquids and Industrial Amine Absorbents: Optimization and Comparative Analysis

Integrated CO2 capture and mineralization technology offers dual benefits by capturing CO2 and converting it into stable carbonates by using materials rich in mineral ions. This process was investigated using dual-functionalized ionic liquids, triethylenetetramine-imidazole ([TETAH][IM]) and diethylenetriamine-imidazole ([DETAH][IM]), as well as industrial amines such as monoethanolamine (MEA) and methyldiethanolamine (MDEA), with calcium oxide (CaO) serving as a mineral ion source. The experiments were conducted at atmospheric pressure for 300 min in in the temperature range of 25–85 °C, absorbent concentrations (0.25–1 M), and absorbent-to-mineralizing agent (liquid-to-solid) ratios (4 mL/g to 10 mL/g). Optimal conditions were identified as 65 °C, 1 M aqueous solution of the absorbent, and a liquid-to-solid ratio of 6 mL/g. Under these conditions, the [TETAH][IM] solution achieved the highest CO2 loading of 4.29 mol of CO2/L solution with 94.03% mineralization efficiency, while the MEA absorbent solution displayed the lowest CO2 loading at 2.45 mol of CO2/L solution with 95% mineralization efficiency. Further, [TETAH][IM] exhibited the highest cyclic CO2 loading efficiency of 92.25%, whereas MEA was not recyclable under the tested conditions. Detailed reaction kinetics were investigated in a batch stirred tank reactorand and the reaction mechanism was proposed based on the characterization of the solid and liquid phases. A preliminary batch-scale cost analysis indicates that CO2 capture and mineralization using T-IM is profitable at $3.77/kg of CO2. However, as it is based on lab-scale data, further rigorous analysis in a continuous stirred reactor is planned for the future. These findings underscore the integrated CO2 capture in aqueous ionic liquid blends along with useful carbonate formation using a mineralizing agent, demonstrating notable advantages over energy-intensive carbon capture in conventional industrial amines and their regeneration.