The
research presented here investigates the reaction mechanism of wollastonite
in situ mineral carbonation for carbon dioxide (CO2) 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 CO2 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 CO2 mineralization
of calcium silicate at the GCS condition, which may enable us to predict
the fate of the injected CO2, and its subsurface geochemical
evolution during the CO2–fluid–rock interaction.