Carbonation of Clay Minerals Exposed to scCO2/Water at 200 degrees and 250 degrees C

• Main Authors: Sugama, T., Ecker, L., Gill, S., Butcher, T. (BNL), Bour, D. (AltaRock Energy, Inc.)
• Other Authors: United States. Department of Energy. Office of Energy Efficiency and Renewable Energy.
• Format: Report
• Language: English
• Published: Brookhaven National Laboratory 2010
• Subjects: By-Products; Leaching; Quartz; Feldspars; Clay; Water Carbonation; Carbon Dioxide; Minerals; Shrinkage; Clays; Montmorillonite; 32 Energy Conservation; Consumption; And Utilization; Kaolinite; Carbonation; Carbonic Acid; Dolomite; Carbonates; Cations; Bentonite; Silicon; Psi; Carbonic acid
• Online Access: https://doi.org/10.2172/1033188; https://digital.library.unt.edu/ark:/67531/metadc831933/

To clarify the mechanisms of carbonation of clay minerals, such as bentonite, kaolinite, and soft clay, we exposed them to supercritical carbon dioxide (scCO2)/water at temperatures of 200 and 250 C and pressures of 1500 and 2000 psi for 72- and 107-hours. Bentonite, comprising three crystalline phases, montmorillonite (MMT), anorthoclase-type albite, and quartz was susceptible to reactions with ionic carbonic acid yielded by the interactions between scCO2 and water, particularly MMT and anorthoclase-type albite phases. For MMT, the cation-exchangeable ions, such as Na+ and Ca2+, present in its basal interplanar space, were replaced by proton, H+, from ionic carbonic acid; thereafter, the cations leaching from MMT directly reacted with CO32- as a counter ion of H+ to form carbonate compounds. Such in-situ carbonation process in basal space caused the shrinkage and breakage of the spacing structure within MMT. In contrast, the wet carbonation of anorthoclase-type albite, categorized as rock minerals, entailed the formation of three amorphous by-products, such as carbonates, kaolinite-like compounds, and silicon dioxide. Together, these two different carbonations caused the disintegration and corruption of bentonite. Kaolinite clay containing the amorphous carbonates and silicon dioxide was inert to wet carbonation. We noted only a gain in weight due to its water uptake, suggesting that kaolinite-like by-products generated by the wet carbonation of rock minerals might remain unchanged even during extended exposure. Soft clay consisting of two crystalline phases, dolomite and silicon dioxide, also was unaltered by wet carbonation, despite the uptake of water.