Modeling Closed Equilibrium Systems of H 2 O-Dissolved CO 2 -Solid CaCO 3 .

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 H2 O-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+ , CO3 2- , HCO3 - , H2 CO3 , 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.