A Novel Approach to Accelerate CO2 Mineralization Storage through CO2 Nanobubbles

Abstract Carbon capture and storage (CCS) technology is a crucial means to address global climate change and reduce atmospheric CO2. CO2 mineralization storage can store CO2 in underground rock formations in a long-term and safe manner, which is the most stable storage method. However, this process may take several decades or even longer, severely constraining the application of CO2 mineralization storage in mining fields. In this work, we propose an innovative approach utilizing CO2 nanobubbles to achieve efficient CO2 mineralization. Chlorite was selected as the experimental sample to compare the effects of carbonated water and CO2 nanobubbles on CO2 storage. Analytical instruments were employed to analyze the rock surface morphology, mineral composition, and ion concentration in the reaction solution post-experiment, revealing the mechanism by which CO2 nanobubbles accelerate the CO2 mineralization rate. Results reveal that CO2 nanobubbles have an average size of 167.6 nm, a Zeta potential of −18.98 mV, and a concentration of 9.4×107 particles/mL. The solution's pH is lower than that of carbonated water, suggesting that the CO2 nanobubble solution enhances the supersaturation level of CO2 in the solution, which facilitates the dissolution of rock minerals. After the reaction of chlorite minerals with CO2, the concentrations of Mg2+, Fe2+, and Al3+ ions initially increased and then decreased, while the concentration of Si4+ ions increased and then stabilized. The ion content in the solution followed the order of Mg2+ > Fe2+ > Si4+ > Al3+. Dissolution processes dominate within the first 1 to 6 days, after which the precipitation rate surpasses the dissolution rate. The surface of chlorite exhibits corrosion features and a new element peak of carbon (C), indicating the formation of inorganic carbonate minerals after the reaction. Thermogravimetric analysis shows that the thermal decomposition of chlorite occurs in two stages: primarily MgCO3 decomposes between 350°C and 650°C, while FeCO3 decomposes between 700°C and 850°C, with a higher content of MgCO3 compared to FeCO3. Compared to carbonated water, the CO2 mineralization rate increased by 17.07% when the reaction solution contained CO2 nanobubbles. This approach can shorten the time required for CO2 mineralization storage, facilitating large-scale CO2 storage. Furthermore, the mechanism of CO2-water-rock interaction is also deeply revealed, which is of great value for understanding the underground CO2 storage process and optimizing the conditions for storage.