Estimation of potential precipitation from an equilibrated calcium carbonate aqueous phase using simple predictive tool

Carbon dioxide (CO₂) sequestration in saline aquifers has been proposed as one of the most practical options for reducing CO₂ emissions into the atmosphere. Massive CO₂ injection into an aquifer would alter the geochemical equilibrium between the rock-forming minerals and the formation water. In this work, a novel and simple predictive tool is presented to estimate the formation of calcium carbonate (CaCO₃) scaling as a function of pH, temperature, ionic strength of the solution, calcium cation concentration, bicarbonate anion concentration, and CO₂ mole fraction when the water mixture is saturated with a gas containing CO₂ to evaluate the effect of solution conditions on the tendency and extent of precipitation. The proposed simple method covers concentrations of calcium cation or bicarbonate anion in the range of 10 to 10 000 mg/L, with temperature ranging between 5 and 90°C, total ionic strength ranging between 0.1 and 3.6, and pH values ranging between 5.5 and 8. The predicted values are found to be in good agreement with the reported data, with average absolute deviations being less than 2.6%. The proposed tool is superior because of its accuracy and clear numerical background based on the Vandermonde matrix, wherein the relevant coefficients can be retuned quickly if more data become available in the future. The simple predictive tool proposed in the paper can be of immense practical value for engineers and researchers to have a quick check on the formation of calcium carbonate scaling when the water mixture is saturated with a gas containing CO₂ at various conditions without opting for any experimental measurements. In particular, process engineers would find the proposed method to be user friendly, involving no complex expressions and presenting transparent calculations.