Synergistic CO₂ Capture and Utilization Using Monoethanolamine Recirculation and Mineral Carbonation with CaO/MgO

Integrating carbon capture, storage, and utilization (CCUS) technologies efficiently and cost-effectively is one of the greatest challenges for industrial decarbonization. This study proposes an integrated and promising solution that combines monoethanolamine (MEA) recirculation with mineral carbonation, maximizing CO2 capture, reducing energy costs related to solvent regeneration, and generating high-value coproducts. Using MEA solutions (10, 20, and 30% v/v) under controlled conditions, CO2 was captured and subsequently mineralized with CaO and MgO (20–80 g/L) at different temperatures (25–70 °C). The process presented a logarithmic kinetic behavior, with rapid initial conversion followed by gradual stabilization, consistent with models used in CO2 capture and supported by pH-dependent mechanisms. The combined process exhibited excellent performance, achieving conversion rates of up to 89% for CaCO3 formation at 80 g/L and 70 °C, results that are consistent with those reported in the literature under similar conditions in laboratory-scale experimental processes. Temperature and oxide concentration were confirmed as critical variables, significantly increasing the occurrence rates and crystal nucleation, as statistically validated through experimental design. Increasing the oxide dosage also prevented resistance to CO2 mass transfer, promoting carbonate transfer. Furthermore, the regenerated MEA solutions maintained physicochemical properties comparable to the original ones, exhibiting strong recirculation potential. The study also has potential limitations in mass transfer in highly concentrated MEA–MgO systems due to gel formation, in agreement with recent findings in the literature. These results demonstrate the predictability and scalability of this integrated CCUS methodology, offering efficient CO2 mitigation with the additional benefit of producing carbonates with distinct crystal morphologies (calcite, magnesite, and nesquehonite). In this way, CO2 stored in the form of carbonates can be applied in the manufacture of products with higher added value, i.e., as inputs for the cement, fertilizer, and pharmaceutical industries.