A comparison of supercritical carbon dioxide and organic solvents for the intercalation of 4-phenylazoaniline into a pillared clay mineral

The intercalation of 4-phenylazoaniline (PAA) in supercritical carbon dioxide (SC-CO2) into montmorillonite (TMA-Mnt) pillared with tetramethylammonium ions at 313 K and 15 MPa was investigated. The adsorption rate and equilibrium PAA uptake were compared with those in n-hexane, CCl4 and benzene solutions at 313 K. The XRD and N-2 adsorption/desorption analyses showed that TMA-Mnt after adsorption of PAA in SC-CO2 had the same pore structure as after adsorption of PAA in normal solvents. SC-CO2 was found to be a good medium for PAA adsorption owing to its having a relatively high adsorption rate and the highest adsorptivity at the same PAA concentration. The properties of PAA adsorption on TMA-Mnt could be well elucidated by the difference in solubility parameters between liquid and solid phases. (C) 2002 Elseviec Science (USA).