Modeling Closed Equilibrium Systems of H2O-Dissolved CO2-Solid CaCO3.

In many places in the world, including North Estonia, the bedrock is limestone, which consists mainly of CaCO3. Equilibrium processes in water involving dissolved CO2 and solid CaCO3 play a vital role in many biological and technological systems. The solubility of CaCO3 in water is relatively low. Depending on the concentration of dissolved CO2, the solubility of CaCO3 changes, which determines several important ground- and wastewater parameters, for example, Ca2+ concentration and pH. The distribution of ions and molecules in the closed system solid H2O-dissolved CO2-solid CaCO3 is described in terms of a structural scheme. Mathematical models were developed for the calculation of pH and concentrations of ions and molecules (Ca2+, CO32-, HCO3-, H2CO3, CO2, H+, and OH-) in the closed equilibrium system at different initial concentrations of CO2 in the water phase using an iteration method. The developed models were then experimentally validated.