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  • 1
    Electronic Resource
    Electronic Resource
    Effect of alkali ions (Na+, K+) on the solvent extraction of uranium(VI) with a di-carboxylated calix[4] arene (1996)
    Springer
    Journal of radioanalytical and nuclear chemistry 210 (1996), S. 87-103 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The solvent extraction of uranium(VI) with a di-carboxylated calix[4]arne (LH2) in chloroform and 1,2-dichloroethane has been studied in the presence or absence of alkali ions (M=Na+,K+). For UO 2 2+ when studied alone, a 1∶2 (metal: ligand) extracted species is evidenced, with a rather low associated extraction equilibrium constant. The efficiency of extraction increases drastically in the presence of alkali ions, due to the formation of heteronuclear complexes. In all cases, the extracted species are found to be both 1∶2∶2 and 1∶1∶2 (UO 2 2+ ∶M∶LH2) mixed complexes, except in chloroform with K+, where only the latter is formed. In the case of Na+, mass spectrometry spectra confirm the existence of both homo and heteronuclear complexes as determined in the extraction studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02055409
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  • 2
    Electronic Resource
    Electronic Resource
    Solvent Extraction of Sodium and Potassium Ions by Dicarboxylated Calix[4]arenes (1997)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 27 (1997), S. 155-168 
    Details
    ISSN: 1573-1111
    Keywords: Dicarboylated calix[4]arenes ; sodium and potassium complexes ; solvent extraction ; selectivity ; 1H-NMR mononuclear and dinuclear species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The extraction of sodium and potassium ions by 25,27-dicarboxymethyl-26,28-dimethoxy-5,11,17,23-tetra-tert-butyl calix[4]arene (L1H2) in chloroform shows the formation of MLIH and M2LI complexes (M = Na, K). In 1,2-dichloroethane, the MLIH species are formed in the acidic pH range, while only the Na2LI species is found at high pH values. The corresponding extraction equilibrium constants K11 (M) and K21 (M) have been evaluated and show a selectivity in favour of Na+ as compared to K+, whatever the nature of the complexes. In chloroform, this selectivity is much more pronounced considering the 2 : 1 complexes: K11(Na)/K11(K)≪ K21(Na)/K21(K). The coexistence of 1 : 1 and 2 : 1 metal : ligand complexes is also shown in the extraction of sodium in 1,2-dichloroethane by the 25,27-dicarboxymethyl-26,28-dimethoxyethoxy-5,11,17,23-tetra-tertbutyl calix[4]arene (LIIH2), locked in the cone conformation. Structural data of the complexes are discussed on the basis of 1H-NMR spectra. In particular, for LIH2, a conformational change from cone to partial cone upon metal complexation has been evidenced for the complexes KLIH, K2LI and Na2LI.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007993200050
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    Paper (German National Licenses)
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