Extração por fase unica : ação de diferentes bases sobre a enolização da tenoiltrifluoroacetona (TTA) e a consequente variação na extração de Ni sistema agua-etanol-metilisobutilcetona (ou ciclohexano)
AUTOR(ES)
Angelo Capri Neto
DATA DE PUBLICAÇÃO
1987
RESUMO
In single-phase extractions the use of diverse bases for the adjustment of acidity of the single-phase solution strongly influences the amount of the metal ion that is extracted. The present work investigates in which way different bases may affect the extent of extraction maintaining the same acidity (as measured by the pH working scale of pHSP). Metal ions are affected differently Thus, Cu is less influenced than Ni when ammonium hidroxide is changed to triethanolamine (TEA). Ni at pHSP 3.0 has its percentage of extraction increased from ca. 5%(NaOH) to, respectively; 23% (ammonia); 31% (monoethanolamine, MEA); 41% (diethanolamine, DEA); and 49% (TEA). The complexation of Ni with thenoyltrifluoroacetonate (TTA) in the single-phase solution is studied with the use of several bases: NaOH. ammonia, sodium acetate, MEA, DEA and TEA. The resulte show that even before the extraction the extent of complexatlon also changes with the base employed, incroasing as the order of basicity decreases. Potenciometric and condutometric tltrations of acid SP solutions with NaOH and TEA, either pure or with the addition of Ni, of TTA and of both Ni and TTA were inconclusive as to why the two bases act dlfferently on the complexation. Spectra of the chelate of Ni-TTA, with the use of either NaOH or TEA, did not show evidence for adduct formation in the presence of the latter. On the other hand, spectra of TTA in single-phase solutions treated with NaOH and with TEA show a marked difference: for the same acidity, TEA enolizes TTA much earlier than NaOH, thus increasing the concentration of the active species at hand for the complexation of the metal ion. A tentative mechanism as to why weaker bases increase the enolizatio of TTA is presented.
ASSUNTO(S)
ACESSO AO ARTIGO
http://libdigi.unicamp.br/document/?code=vtls000047001Documentos Relacionados
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