Extraction of metal ions from liquid and solid materials by supercritical carbon dioxide

Abstract

Supercritical fluid extraction (SEE) of organic compounds has been the subject of many studies in recent years.1•2 A suitable solvent for this purpose is carbon dioxide due to its moderate critical constants (Tc = 31.1 °C, Pc = 72.8 atm), inertness and easy availability in purified form. Little

Spectroscopy, modeling and computation of metal chelate solubility in supercritical CO{sub 2}. Annual progress report, September 15, 1996--September 14, 1997

“…Although the solubility of water in CO 2 is less than 1 mole % (Dohrn et al, 1993) our investigations show that it may have substantial influence on the stability of some metal chelate complexes. In addition, several researchers have found that the addition of a small amount of water can significantly increase the extraction efficiency of metals from solid matrices with supercritical CO 2 (Laintz et al, 1992;Lin et al, 1994;Lin et al, 1995b;Phelps et al, 1996). Thus, understanding the effects of water on metal chelate stability and solubility is vitally important.…”

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 .…”

“…[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 . 2 Of the previously-known metal chelating agents, 8-hydroxyquinoline (8-HQ) is interesting as it can produce stable metal complexes with various metal ions in organic solvents.…”

Extraction of Chromium(III) and Chromium(VI) Species from Solid Matrices Using Green Solvent Supercritical Carbon Dioxide

“…[13][14][15] Direct extraction of metal ions by ScCO2 is highly inefficient because of the charge neutralization requirement that causes weak solvent-solute interactions. When metal ions are bound to organic ligands, however, they become quite soluble in ScCO2.…”

“…When metal ions are bound to organic ligands, however, they become quite soluble in ScCO2. In 1992, Laintz et al 13 first reported the extraction of Cu(II) from liquid and solid materials using ScCO2 containing lithium bis(trifluoroethyl)dithiocarbamate (LiFDDC) as an extractant. Using 8-hydroquinoline as a chelating agent, Cr(III) has been successfully removed from solid samples in ScCO2.…”