Correlation of solid solubility of 1,4-bis(alkylamino)-9,10-anthraquinones in supercritical carbon dioxide using solution model approach

In this study, solid solubility data of six 1,4-bis(alkylamino)-9,10-anthraquinones (AQs) in supercritical carbon dioxide (CO2) are correlated using a two-parameter solution model developed from the regular solution model coupled with the Flory–Huggins equation. This two-parameter solution model yields satisfactory correlated results comparable to those from commonly used three-parameter semi-empirical equations. The average deviation in correlated solubilities using our two-parameter solution model is about 6%. With appropriate model simplification and generalization procedure, a predictive solution model is proposed in this study for solubility prediction using the chain length of alkyl group of alkylamino side chain. The proposed predictive solution model provides acceptable predicted results and yields average deviation in predicted solubilities of 17%. In addition, the proposed predictive solution model is also employed to predict the solubility data of AQs that are not originally included in the generalization procedure. The calculated results obtained in this study demonstrate that the solution model adopted in this study is applicable for correlation and prediction of solid solubilities of structure-related compounds in supercritical CO2.