Solubility of individual polychlorinated biphenyl (PCB) congeners in supercritical fluids: CO₂, CO₂/MeOH and CO₂/n-C₄H₁₀

The solubilities of nine individual polychlorinated biphenyl (PCB) congeners 2-chlorobiphenyl, 4-chlorobiphenyl, 2,2′-dichlorobiphenyl, 4,4′-dichlorobiphenyl, 2,4′,5-trichlorobiphenyl, 3,3′,4,4′-tetrachlorobiphenyl, 2,2′,4,5,5′-pentachlorobiphenyl, 2,2′,4,4′,5,5′-hexachlorobiphenyl, and 2,2′,3,4,4′,5,5′-heptachlorobiphenyl in supercritical carbon dioxide and in supercritical carbon dioxide modified by n-butane (n-C₄H₁₀) and methanol (0.05 mole fractions on a solute-free basis) are presented. The concentrations of the PCB/hexane solutions are analyzed by capillary gas chromatography with an electron capture detector (GC/ECD). Solubility isotherms at 313, 323, and 333 K for each PCB congener have been determined over a pressure range of 100-300 bar. The solubility data (expressed as mole fractions) are correlated by a semi-empirical equation to link the solubility to the thermodynamic properties of solvent such as reduced density, solute vapor pressure, reduced temperature and reduced pressure of the system. Both n-butane and methanol were found to increase the solubility over the case of pure carbon dioxide of all PCB congeners studied (higher in CO₂/n-C₄H₁₀ fluids).