Extraction of Toxic Heavy Metals Using Supercritical Fluid Carbon Dioxide Containing Organophosphorus Reagents

Abstract

The feasibility of using Kelex 100, Cyanex 272, 301 and 302, and D2EHTPA as reagents for the supercritical fluid extraction of toxic heavy metals is demonstrated. High extraction efficiencies are observed for a range of heavy metals using Cyanex 301 and 302 and D2EHTPA ligands from a variety of matrices and from samples of high acidity. Extraction efficiencies increased with increasing pressure. Solubility of a range of complexes was determined and found to vary between 0.15 and 12 g L-1. The extraction of toxic metals from environmental matrices was shown to be efficient for a range of metals using the Cyanex 302 ligand. Kelex 100 was found to be very selective for the extraction of Cu2+ using supercritical fluid CO2. In many cases the extraction process did not quantitatively remove the metals, but the extraction profiles were demonstrated to be initially rapid followed by a very low level of metal extraction, indicating a limit of the extraction process to leachable toxic metals.