Reaction Mechanism of Wollastonite In Situ Mineral Carbonation for CO2 Sequestration: Effects of Saline Conditions, Temperature, and Pressure

The research presented here investigates the reaction mechanism of wollastonite in situ mineral carbonation for carbon dioxide (CO 2 ) sequestration. Because wollastonite contains high calcium (Ca) content, it was considered as a suitable feedstock in the mineral carbonation process. To evaluate the reaction mechanism of wollastonite for geological CO 2 sequestration (GCS), a series of carbonation experiments were performed at a range of temperatures from 35 to 90 °C, pressures from 1500 to 4000 psi, and salinities from 0 to 90,000 mg/L NaCl. The kinetics batch modeling results were validated with carbonation experiments at the specific pressure and temperature of 1500 psi and 65 °C, respectively. The results showed that the dissolution of calcium increases with increment in pressure and salinity from 1500 to 4000 psi and 0 to 90000 mg/L NaCl, respectively. However, the calcium concentration decreases by 49%, as the reaction temperature increases from 35 to 90 °C. Besides, it is clear from the findings that the carbonation efficiency only shows a small difference (i.e., ±2%) for changing the pressure and salinity, whereas the carbonation efficiency was shown to be enhanced by 62% with increment in the reaction temperature. These findings can provide information about CO 2 mineralization of calcium silicate at the GCS condition, which may enable us to predict the fate of the injected CO 2 , and its subsurface geochemical evolution during the CO 2 -fluid-rock interaction.