(418ax) Fixation of CO2 into Solid Mineral Matrix Via in-Situ and Ex-Situ Enhanced Weathering

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.