Morphology changes of phlogopite under geologic co₂ sequestration conditions

To apply geologic CO₂ sequestration effectively, a better understanding of the reactions between injected CO₂ and formation rocks is needed. In this work, both fluid/solid chemistry analysis and interfacial topographic studies were used to investigate the dissolution of phlogopite (KMg₃Si₃AlO₁₀(F,OH)₂), which served as a model for the widely distributed aluminum-silicate minerals in potential CO₂ sequestration sites. Incongruent dissolution of phlogopite was observed in both water/CO₂/phlogopite and 1M NaCl/CO₂/phlogopite systems. Although the bulk solution was not oversaturated with any secondary mineral phase within 159 h, precipitation did occur on phlogopite surfaces, as evidenced in AFM images. In NaCl solution, precipitation first appeared on the edges of dissolution pits and then relocated to other areas. During the reaction, the dissolution pits became bigger and gradually connected with each other. The result of this research provides new information on the kinetics and mechanisms of the interfacial reactions between CO₂ and sequestration rocks.