The solvent extraction of metal ions by crown compounds

Takeda, Yasuyuki

doi:10.1007/3-540-12821-2_1

Cited by 103 publications

(6 citation statements)

References 97 publications

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“…Although literature on ion-pairing in nitrobenzene is scarce, one may compare with K ip(CsPicrate) = 602−1510 for the extraction of cesium picrate into nitrobenzene . It is known that complexed salts in polar solvents often behave as strong electrolytes, , at least for cation complexation, in accord with the ligand-shielding effect . Indeed, we have seen in the extraction of Li + by a crown ether in 1-octanol that ion-pairing with Cl - decreases from 1.3 × 10 4 for the free ions in the water-saturated 1-octanol to 5.4 × 10 3 for the complex with the anion .…”

Section: Discussionmentioning

confidence: 86%

Calix[4]pyrrole: A New Ion-Pair Receptor As Demonstrated by Liquid−Liquid Extraction

et al. 2008

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Solvent-extraction studies provide confirming evidence that meso-octamethylcalix[4]pyrrole acts as an ion-pair receptor for cesium chloride and cesium bromide in nitrobenzene solution. The stoichiometry of the interaction under extraction conditions from water to nitrobenzene was determined from plots of the cesium distribution ratios vs cesium salt and receptor concentration, indicating the formation of an ion-paired 1:1:1 cesium:calix[4]pyrrole:halide complex. The extraction results were modeled to evaluate the equilibria inherent to the solvent-extraction system, with either chloride or bromide. The binding energy between the halide anion and the calix[4]pyrrole was found to be about 7 kJ/mol larger for cesium chloride than for the cesium bromide. The ion-pairing free energies between the calix[4]pyrrole-halide complex and the cesium cation are nearly the same within experimental uncertainty for either halide, consistent with a structural model in which the Cs+ cation resides in the calix bowl. These results are unexpected since nitrobenzene is a polar solvent that generally leads to dissociated complexes in the organic phase when used as a diluent in extraction studies of univalent ions. Control studies involving nitrate revealed no evidence of ion pairing for CsNO3 under conditions identical to those where it is observed for CsCl and CsBr.

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Section: Discussionmentioning

confidence: 86%

Calix[4]pyrrole: A New Ion-Pair Receptor As Demonstrated by Liquid−Liquid Extraction

et al. 2008

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“…1), frequently designated as A and B, respectively, are isolated in the highest yields. It is now well established that these two isomers differ in their complexation behavior toward mono-and divalent cations in aqueous Solution [10] and, therefore, in their ability to extract these ions from aqueous Solution into an immiscible organic solvent [6], To date, however, most extraction studies involving DCH18C6 [14][15][16][17][18][19] have employed halogenated hydrocarbon solvents, picrate counterions, low aqueous acidities, or other experimental conditions that preclude application of the results obtained to process-scale metal ion separations, such as those involved in the treatment of acidic nuclear wastes. As a consequence, the practical Utility of these studies has been limited.…”

Section: Introductionmentioning

confidence: 99%

Isomer Effects in the Extraction of Metal Ionsfrom Acidic Nitrate Media by Dicyclohexano-18-crown-6^†

et al. 1999

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The extraction of Strontium and potassium from nitric acid by the cis-syn-cis and cis-anti-cis isomers of dicyclohexano-18-crown-6 (DCH18C6) in 1-octanol is examined. Both isomers are shown to extract significant amounts of undissociated nitric acid. This extraction, along with the formation of metal-nitrato and metal-crown ether complexes in the aqueous phase, is shown to be important in determining the efficiency of metal ion extraction by the two isomers. The DCH18C6 isomer yielding the more efficient extraction of potassium or Strontium is shown to depend upon the crown ether concentration and the aqueous nitric acid concentration.

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“…7 The neutral oxodonor molecules are also capable of forming outer-sphere complexes, in the presence of large organophilic anions such as picrate (which act as counter ions) and lead to unusual trends in metal ion extractions . 8 We have also reported such uncommon extraction behavior of Am 3+ and UO22+ with both TBP and DOSO using picrate as the counter anion Am 3+ being better extracted than U022+. 9 To investigate the cause of the reversal vis-a-vis the role of water molecules in the inner co-ordination sphere, the thermodynamic parameters of the two-phase extraction equilibria were determined in the present work.…”

Section: Introductionmentioning

confidence: 90%

The unusual extraction behavior of americium(III) and dioxouranium(VI) from picric acid medium using neutral oxodonors II. A thermodynamic study

Mohapatra

Manchanda

1999

J Radioanal Nucl Chem

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The role of temperature on the distribution of Am 3+ and UO22+ was investigated in the extraction systems involving TBP and DOSO as the neutral oxodonors and picrate as the organophilic counter anion. The inner-sphere water molecules and their substitution by the oxodonor molecules appeared to influence the extraction constants of these metal ions. The conditional extraction constants for Am 3+ were found to be larger (about 3 order of magnitude) than those for UO22+. From the thermodynamics data it appeared that both TBP as well as DOSO bind Am 3+ ion through outer-sphere coordination. In presence of IM NaC1, though the interaction with TBP remains unaltered DOSO tend to form an inner-sphere complex. On the other hand, UQ2 2+ forms inner-sphere complexes with DOSO and outer-sphere complex with TBP in the absence of salt. In the presence of IM NaC1, both TBP and DOSO form inner-sphere complexes. The effect of ionic strength on metal ion extraction was also investigated.

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The solvent extraction of metal ions by crown compounds

Cited by 103 publications

References 97 publications

Calix[4]pyrrole: A New Ion-Pair Receptor As Demonstrated by Liquid−Liquid Extraction

Calix[4]pyrrole: A New Ion-Pair Receptor As Demonstrated by Liquid−Liquid Extraction

Isomer Effects in the Extraction of Metal Ionsfrom Acidic Nitrate Media by Dicyclohexano-18-crown-6^†

The unusual extraction behavior of americium(III) and dioxouranium(VI) from picric acid medium using neutral oxodonors II. A thermodynamic study

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The solvent extraction of metal ions by crown compounds

Cited by 103 publications

References 97 publications

Calix[4]pyrrole: A New Ion-Pair Receptor As Demonstrated by Liquid−Liquid Extraction

Calix[4]pyrrole: A New Ion-Pair Receptor As Demonstrated by Liquid−Liquid Extraction

Isomer Effects in the Extraction of Metal Ionsfrom Acidic Nitrate Media by Dicyclohexano-18-crown-6†

The unusual extraction behavior of americium(III) and dioxouranium(VI) from picric acid medium using neutral oxodonors II. A thermodynamic study

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Isomer Effects in the Extraction of Metal Ionsfrom Acidic Nitrate Media by Dicyclohexano-18-crown-6^†