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 Cu 2+ using supercritical fluid CO 2 . 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.

Recovery of precious metals from spent automobile catalytic converters using supercritical carbon dioxide

“…Solubilisation of the metal complex into the supercritical fluid is then possible. [22,28,29] Effect of extraction pressure Pressure, which determined the solvent power of the supercritical fluid, is an important parameter for the sc CO 2 extraction of metals. Figure 3 shows the results of the effect of pressure on extraction efficiency.…”

A Review of Rare Earth Mineral Processing Technology

“…104 Most researchers are interested in REEs by SCF technique, in which, REEs extraction are expected to be improved by means of increasing the mass transfer between CO 2 and REEs. [104][105][106][107][108][109][110][111] The rapid and complete removal of the solute from the solvent is attained by means of gasification of carbon dioxide at atmospheric pressure, after the extraction. Shimizu and team had investigated RE extraction from secondary resources by employing supercritical fluid method.…”

Highly CO2-soluble 5-Amido-8-hydroxyquinoline Chelating Agents for Extraction of Metals in Sc-CO2

“…Recently, in an attempt to find readily available and highly efficient chelating agents for removal of metals from matrices in Sc-CO 2 , various compounds were tested, and some of these appeared to have potential for real application, such as dithiocarbamates, [6][7][8] β-diketones, 9,10 organophosphorous reagents, 5,11 macrocyclic compounds, 12,13 and fluorinated surfactants. [6][7][8]14 To choose appropriate chelating agents for use in Sc-CO 2 , good CO 2 -solubility and chemical stability are obviously required because low CO 2 solubility and chemical instability have been significant obstacles for the employment of chelating agents in Sc-CO 2 .…”