Table 1 Summary of key findings of thermodynamic observations

CO₂ Pressure (50–500 atm)

Higher pressure increases CO₂ solubility, leading to more bicarbonate (HCO₃⁻) formation and CaCO₃ precipitation

Precipitation rate increases significantly at 500 atm

Temperature (274–298 K)

Higher temperatures promote aragonite formation due to the slightly lower stability of calcite at elevated temperatures.

Aragonite is more likely to form above 298 K

Salinity (TDS up to 19,000 ppm)

Higher salinity reduces CO₂ solubility but increases solution alkalinity, promoting CaCO₃ precipitation.

Seawater enhances precipitation more than NaCl solutions

pH (6.5–8.5)

Optimal pH range for CaCO₃ precipitation. Extreme pH changes may lead to impurity formation (e.g., dolomite, huntite)

pH above 8.5 favours CaCO₃ formation but may reduce purity

Mg²⁺ and SO₄²⁻ Ions

Mg²⁺ can incorporate into carbonate structures, forming dolomite/huntite; SO₄²⁻ can lead to gypsum precipitation

Control of Mg²⁺/Ca²⁺ ratios is essential for purity.

Supersaturation Index (S)

Higher saturation levels accelerate precipitation, but excessive supersaturation can lead to secondary mineral formation.

Maintaining moderate saturation prevents impurity formation.