Dissolving Technique of polar compounds into supercritical COィイD22ィエD2

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Supercritical carbon dioxide (scCOィイD22ィエD2) extraction of alkali metal ions from aqueous solutions (K+, Na+ : 1.7 x 10ィイD1-4ィエD1 mol dmィイD1-3ィエD1) with ligands was investigated. Conditions of the experiments were 40℃ with pressure ranging from 10 Mpa to 18 Mpa. Ligands used were crown ethers (18-crown-6, cis-dicyclohexyl-18-crown-6 and 15-crown-5) and glymes (triglyme and tetraglyme). Extraction of KィイD1+ィエD1 or NaィイD1+ィエD1 with ligand in scCOィイD22ィエD2 gave negligibly low recoveries that did not vary with pressure. However, in the presence of an additive, pentadecafluoro-n-octanoic acid (HPFOA), the recoveries increased clearly for both sodium and potassium ion extractions. This is because the HPFOA ionized and apparently supplied its anion which has COィイD22ィエD2-philic fluoro-alkyl chains. Based on the experimental results, a chemical equilibrium model was developed to analyze the extraction mechanism. For crown ether systems, the recoveries showed simple behavior, and the extracted complexes (alkali metal ion : ligand : counter ion) were confirmed to be monomeric (1:1:1). For glymes systems, the recoveries showed various behavior and tended to decrease at high ligand concentrations. This seemed to indicate consecutive complex formation in the aqueous phase. The results of this study show that alkali metals can be extracted with scCOィイD22ィエD2 using ligands and recovery of the metals can be greatly increased by adding a substance that can supply a COィイD22ィエD2-philic counter Ion.Rerading the reverse micell formation, an apparatus for in-situ dynamic laser scattering measurement was developed. With this apparatus, it was found that perfluoro-polyether can be a good surfactant for reverse micell in carbon dioxide in the presence of warer, however direct evidence of the micell could not be obtained because of lackness in agitation power of the experimental setup.