Supercritical Fluid Adsorption Of Artemisinin

A review has been accomplished for the advances in some supercritical techniques, including studies on solubility in supercritical fluid, supercritical fluid adsorption (SFA) in the recent 10 years.An apparatus has been built for studying supercritical adsorption and desorption behavior of solid on sorbent, and it can be used to measure solubility of solid in supercritical fluid. The solubility of artemisnin in supercritical carbon dioxide ( SC-CO2) was measured in a pressure range (10-27) MPa and from (310.1 to 338.1) K. The range of solubility of artemisinin in SC-CO2 is 9.8 x 10-5 to 2.7 x 10-3 mol/mol. It can be affirmed that at pressure from (19-27) MPa, the solubility increase with the increasing of pressure or temperature. At pressure from (10-19) MPa, the solubility increase with pressure and decrease with increasing temperature. According to the molecular association assumption, a four parameters molecular association model for solids has been inferred, in which the phase equilibrium was considered. This model leads to a good agreement with the experimental values. The average absolute relative derivation is 4.24 %.The adsorption isotherms at 308.1. 318.1 and 328.1 K for artemisinin on silica gel form SC-CO2 were determined by frontal analysis chromatography when pressures were fixed at 14.1, 16.1 and 18.1 MPa. The adsorption isotherms were fitting by the Freundlich model with the average derivation of less than 2.4 %. The equilibrium adsorption capacity of artemisinin on silica gel increases as temperature increases at fixed pressure. However the equilibrium adsorption capacity decreases as temperature increases at fixed densities. And the equilibrium adsorption capacity decreases as pressure increases when the temperature and concentration are constant. As discussed above, the behavior of adsorption equilibrium strongly depends on the solubility of(2003;artemisisinin in SC-COi, however the competitive phenomenon between the artemisinin and CC>2 towards the active sites of the adsorbent can't be neglected.The influences of temperature, pressure and flow rate on desorption artemisinin from silica gel by SC-CCh were studied. The desorption efficiency for this system increases with pressure and the optimal operation temperature is 308 K at fixed pressure. Overall the desorption process of artemisinin from silica gel using SC-C02 is favorable with the most removal about 92 %.