Calculation of Solid Solubility of Complex Molecules in Supercritical Carbon Dioxide using a Solution Model Approach

Solid solubility of complex molecules in supercritical carbon dioxide was calculated using a solution model approach. These solutes include the biological compounds of antioxidants, steroids, vitamins, and heavy aromatics. The modified AD (m-AD) activity coefficient model proposed in our previous study [Cheng, J.S., Tang, M. and Chen, Y.P. “Correlation and comparison of the infinite dilution activity coefficient on aqueous mixtures from a modified excess free energy model” Fluid Phase Equilib. (2002) Submitted for publication] coupled with the Flory-Huggins equation was employed. The molar volume of the solutes in the supercritical phase and the solid–fluid interaction parameter were optimally fitted for each solid component. Satisfactory results were obtained from the m-AD model with three or four parameters. The overall accuracy in this study is comparably good to that from the conventional equation of state method or the semi-empirical correlation equation. This result suggests a feasible high-pressure solid solubility calculation with the application of a theoretically based solution model.