387790 Fixation of CO2 into Solid Mineral Matrix Via in-Situ and Ex-Situ Enhanced Weathering

Tuesday, November 18, 2014
Galleria Exhibit Hall (Hilton Atlanta)
Greeshma Gadikota, Earth and Environmental Engineering & Chemical Engineering, Columbia University, New York, NY and Ah-Hyung Alissa Park, Earth and Environmental Engineering, Columbia University, New York, NY

One of the proposed technologies to permanently store CO2 is to react calcium and magnesium bearing silicate minerals such as olivine ((Mg,Fe)2SiO4), serpentine (Mg3(OH)4(Si3O5)), wollastonite (CaSiO3), anorthite (CaAl2Si2O8), labradorite ((Ca,Na)(Al,Si)4O8), and basalt (rocks comprising various calcium and magnesium bearing minerals) to form calcium and magnesium carbonates, which are thermodynamically stable and insoluble in water. Permanent carbon storage can occur by directly injecting CO2 into geologic formations containing these calcium and magnesium bearing silicate minerals and rocks, which is known as in-situ carbon mineralization or by mining and crushing these minerals for converting these minerals into carbonates via ex-situ carbon mineralization. Regardless of whether carbon storage occurs via in-situ or ex-situ schemes, it is essential to understand the reaction mechanisms and time scales of CO2-reaction fluid-mineral interactions which can vary significantly depending on the temperature, partial pressure of CO2, presence of additives, and pH. The chemical changes in minerals also impact the morphological characteristics such as porosity and surface area. The reaction mechanisms also differ when CO2 hydration, mineral dissolution, and formation of carbonates occur simultaneously in a single step carbonation process, and when these reactions are decoupled such that mineral dissolution and formation of carbonates are carried out separately at low and high pH, respectively, which favor these individual reaction steps. Therefore, this study aims to provide a comparison of the kinetics of CO2-reaction fluid-mineral interactions at temperatures as high as 185 oC, pressures as high as 175 atm, in the presence of various additives such as salts (e.g., NaCl, NaHCO3), and chelating agents (e.g., Na-oxalate). In addition, modeling approaches that incorporate coupled chemical and morphological changes from CO2 interactions with minerals are discussed to predict the fate of CO2 interactions with minerals over time.

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