Copper(II) removal from aqueous solutions by chelation in supercritical carbon dioxide using fluorinated beta-diketones

Copper removal from aqueous solutions by chelation in supercritical carbon dioxide was investigated. The chelating agents were 1,1,1-trifluoroacetylacetone (TFA) and 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedione (FOD). Extraction efficiencies were determined for a single equilibrium stage in the temperature range 308-328 K and the pressure range 9.9-24.0 MPa and ranged from 4% to 84%. The extraction efficiencies increased with increasing the initial amount of chelating agent and with decreasing the initial copper concentration. No significant changes in extraction efficiencies were observed with temperature and pressure at a fixed initial amount of chelating agent. A thermodynamic model based on combined reaction and phase equilibria was also developed for prediction of extraction efficiencies.