Modelling solubility of CO2 into pure water and electrolites aqueous solutions

A semiempirical model is presented which is used to calculate the effect of temperature and pressure on carbon dioxide solubility in pure water and various aqueous electrolyte systems. The model was developed by using of the modern definition of the Henry's constant and Pitzer interaction model. It takes into account chemical reactions as well as physical inteactions. Pitzer's ion-interactions parameters was. evaluated by least-squares fitting to available P-T-X data for carbon dioxide in single salt aqueous solutions. The resulting model is validated by comparing calculated and measured solubilities of carbon dioxide in pure water and in NaCl solutions up to 6 m, CaCl2 solutions up to 2.5 m and MgCl2 solutions up to 4 m. The agreement between the calculated and measured solubilities is typically better than 10% up to 433 K and 90 bar. The relevance of temperature and pressure corrections to the activity coefficients of gaseous components and aqueous solutes is discussed in regard to the assumed accuracy with which geochemical models are able to calculate gas and mineral solubilities in natural water systems.