タンタル-弗酸-TBP系におけるタンタルの抽出機構について

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タイトル別名
  • The Mechanism of Tantalum Extraction in Tantalum-Hydrofluoric Acid-Tributyl Phosphate System
  • タンタル-フツサン-TBPケイ ニ オケル タンタル ノ チュウシュツ キコウ ニ ツイテ

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The mechanism of Ta extraction by TBP in Ta-Hydrofluoric acid-TBP (tributyl phosphate) system was investigated in this report. The results obtained can be summarized as follows: (1) Ta present at lower HF acidity seemed to be essentially HTaF6, at higher HF acidity H2TaF7, and at still higher HF acidity H3TaF8. (2) One molecule of Ta compounds present at various HF acidity combined with three molecules of TBP organic solvent, and was extracted by TBP in the form of Ta compound-3 TBP complex. (3) At higher degree of polymerization of Ta in aqueous phase than in organic phase, the Ta distribution coefficient and the percentage of Ta extracted became lower. At higher HF acidity the Ta polymerization number in aqueous phase was constant and larger than that in organic phase, independent of the influence of Ta concentration in aqueous phase, but of lower HF acidity, the ratio of polymerization number in aqueous phase to that in organic phase was larger at higher Ta concentration, but was smaller at lower Ta concentration. (4) The process of Ta-HF-TBP extraction was exthothermic reaction, and the heat of extraction was 2.41 kcal/mol in the condition of 6.36N HF acidity and Ta concentration of 16 g/L. (5) The rate-controlling step in the extraction of Ta in Ta-HF-TBP extractive system seemed to be the formation reaction of Ta compound-3TBP complex. (6) In this extractive system, the Ta concentration in aqueous phase dependent on the distance from the interface showed little change, but the change in TBP phase was remarkable. (7) The activation energy for diffusion of Ta species present in 1.28N HF solution was 3.495 kcal/mol, and that of Ta compound-3TBP complex in TBP phase was 5.836 kcal/mol.

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