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 CaCO 3 . Equilibrium processes in water involving dissolved CO 2 and solid CaCO 3 play a vital role in many biological and technological systems. The solubility of CaCO 3 in water is relatively low. Depending on the concentration of dissolved CO 2, the solubility of CaCO 3 changes, which determines several important ground- and wastewater parameters, for example, Ca 2 + concentration and pH. The distribution of ions and molecules in the closed system solid H 2 O–dissolved CO 2 –solid CaCO 3 is described in terms of a structural scheme. Mathematical models were developed for the calculation of pH and concentrations of ions and molecules (Ca 2 +, CO 3 2 –, HCO 3 –, H 2 CO 3, CO 2, H +, and OH – ) in the closed equilibrium system at different initial concentrations of CO 2 in the water phase using an iteration method. The developed models were then experimentally validated.