Extraction and Separation of Tantalum and Niobium by Liquid-Liquid Extraction in the HF-H₂SO₄-TBP System

抄録

The method for extracting and separating Ta and Na by using the solvent extraction system, hydrofluoric acid-sulfuric acid-tributyl phoshate (TBP), was investigated. The extractability of fluotantalates and fluoniobiates from HF-H₂SO₄ solution into TBP was found to be functions of HF acidity, H₂SO₄ acidity, TBP concentration, oxide concentration, organic solvent ratio, and extraction frequency. The results obtained can be summarized as follows: (1) The Ta percentage extraction and the Ta distribution ratio increased with the increase of H₂SO₄ acidity at a const HF acidity, but decreased with the increasing HF acidity at a constant H₂SO₄ acidity. They diminished with the decrease of TBP concentration. The Nb percentage extraction and the Nb distribution ratio augmented with increasing HF acidity, H₂SO₄ acidity, and TBP concentration. (2) In general, the separation coefficient was superior in low HF acidity-low H₂SO₄ acidity, being inferior at high HF acidity-high H₂SO₄ acidity. It was little varied by TBP concentrations. (3) The percentage extractions of Ta and Nb fell with the increase of oxide concentration of aqueous solution. (4) The augmenting volume ratio of solvents and the frequency of extraction caused increases of the percentage extractions of Ta and Nb. (5) The extract made with TBP contained little impurities. (6) The HF-H₂SO₄-TBP system has larger extractability of Ta and Nb, particulary Nb, and is higher in purity the organic extract than the HF-H₂SO₄-hexone system which is being used as the industrial extraction system for liquid-liquid extraction of Ta and Nb.