Solubility of anthraquinone derivatives in supercritical carbon dioxide

Solubility data of 1-amino-4-hydroxyanthraquinone and 1-hydroxy-4-nitroanthraquinone in supercritical carbon dioxide have been measured at the temperature of 323.15, 353.15 and 383.15 K and over pressure ranges 12.5-25.0 MPa by a flow - type apparatus. The solubility of 1-amino-4-hydroxyanthraquinone was significantly higher than that of 1-hydroxy-4-nitroanthraquinone. It was found that amino group in 1-amino-4-hydroxyanthraquinone can enhance the solubility of anthraquinone derivatives in supercritical carbon dioxide compared with nitro group in 1-hydroxy-4-nitroanthraquinone. The experimental results were correlated satisfactorily by four types of the density-based models, namely, Mendez-Santiago-Teja, Kumar-Johnston, Chrastil, and Sung-Shim. Moreover accurate representation of the solubility of anthraquinone dyestuffs was obtained by the regular solution model with the Flory-Huggins theory as well as the Peng-Robinson equation of state modified by Stryjek and Vera with the van der Waals one-fluid mixing rule.