Application of a gas-liquid entraining rotor to supercritical fluid extraction Removal of iron (III) from water

摘要

Supercritical fluid extraction (SFE) of aqueous solutions is often limited by poor mass transport. The performance of a new gas-liquid entraining device was investigated to improve mass transport and thereby increase extraction efficiency. As a test system, iron (III) was extracted from wather with a beta-diketone chelating agent (HL) and supercritical fluid carbon dioxide. Metal beta-diketonate complexes with sufficient solubility in supercritical fluid CO_2 are often poorly extracted from aqueous solutions due to limjited mass transport between the water-soluble metal ion and the CO_2-soluble chelating agent. The new entraining device maximizes contact between the ligand-rich CO_2 phase and the metal ion-rich aqueous phase. Iron (III) was extracted from water with the chelating agent 2,2,7-trimethyl-3,5-octanedione (H(tod)) and supercritical fluid CO_2 at 60 deg C and 20.8 MPa. With entrainment, 79% of the iron was removed from the aqueous phase. This represents a three-fold increase in iron extraction efficiency over that of a static system.