Solubility of disperse dyes in supercritical carbon dioxide and ethanol

The aim of this work is the investigation of the solubility of three disperse dyes in a mixture of CO2 and ethanol. Experimental solubilities of disperse blue 79, disperse orange 3 and solvent brown 1 in a mixture containing 5.5 mol% of ethanol in carbon dioxide have been measured using a dynamic apparatus and compared with those in pure carbon dioxide [A. Ferri, M. Banchero, L. Manna, S. Sicardi, J. Supercrit. Fluids 30 (2004) 41–49]. The effect of the co-solvent is so pronounced that solubilities similar to those measured in pure carbon dioxide have been achieved in the mixture at pressures 100 bar lower. The experimental results have been correlated with three different approaches: the Peng–Robinson equation of state [D.Y. Peng, D.B. Robinson, Ind. Eng. Chem. Fundam. 15 (1976) 59–63], the semi-empirical Chrastil equation modified for ternary systems [J.C. Gonzales, M.R. Vieytes, A.M. Botana, J.M. Vieites, L.M. Botana, J. Chromatogr. A 910 (2001) 119–125] and, finally, a correlation recently proposed by our research group for binary systems [A. Ferri, M. Banchero, L. Manna, S. Sicardi, J. Supercrit. Fluids 32 (2004) 27–35] here applied for the first time to ternary systems. The results have pointed out that the third semi-empirical equation gives the best agreement between the experimental and calculated solubilities.