Prediction of CO₂ solubility in multicomponent electrolyte solutions up to 709 bar: Analogical bridge between hydrophobic solvation and adsorption model

Prediction of CO₂ solubility in electrolyte solution is important for the design of various industrial processes using CO₂. A large amount of experimental data is needed to predict the solubility accurately, as a consequence of the complex composition of electrolyte solution. 1384 experimental CO₂ solubility data in various electrolyte solutions (containing mostly Na⁺, Ca²⁺, Mg²⁺, K⁺, SO₄²⁻, and Cl⁻) from 30 references were used as training and validation data for developing a solubility model. According to the analogy between the hydrophobic solvation of CO₂ and the adsorption phenomena, the novel solubility model with only four parameters (m₀, α, k₀, and k₁) was developed to predict the CO₂ solubility in solution with various ions. The model was correlated with the CO₂ pressure and system temperature. The effect of dissolved electrolytes on the CO₂ solubility was indicated by the concentration of electrostricted water molecule (h_a) in the model, which was calculated using the concentration and hydration number of dissolved ions. The developed model with four parameters—obtained from experimental CO₂ solubility data in water and single-salt solutions—reproduced the CO₂ solubility well in complex electrolyte solutions, including the solutions after CO₂–brine–rock reactions. Of the 1384 data, 94% were within a 95% prediction interval of the model. The model parameters can be used to estimate the heat of CO₂ solvation, maximum CO₂ solubility in water, and decay constant of the CO₂ solubility with respect to the h_a value. The developed model was further validated with single-salt solutions containing minor ions such as Li⁺ or Br⁻.