Partial molar volume fraction of solvent in binary (CO2–solvent) solution for solid solubility predictions

Prediction of solid solute solubility in an organic solvent with dissolution of dense CO2 as antisolvent is important for the design of antisolvent crystallization processes. A new model is proposed in this work to predict the mole fraction of a pure solid solute in a ternary (CO2–solvent–solid) system at solid–liquid equilibrium. This is based on the hypothesis that CO2 molecules cluster around the solvent molecules at high values of CO2 mole fraction. As a result the solvent molecules proportionately lose their affinity for the solid solute molecules. Accordingly the solid mole fraction in a solution is considered to be proportional to the partial molar volume fraction (PMVF) of the solvent in the binary (CO2–solvent) liquid solution or the solventʹs contribution to the molar volume of the binary system. This model enables prediction of the liquid phase composition of the ternary system using only the binary information. The model has been validated, by predicting the solid solubility in various organic solvents, in good agreement with the corresponding experimental data from the literature, for several solids, such as β-carotene, cholesterol, acetaminophen, as well as naphthalene, phenanthrene and salicylic acid. The performance of this model is found to be better than an earlier method, which uses the partial molar volume (PMV) of solvent in the CO2–solvent mixture.