METHOD OF SEPARATING TANTALUM AND NIOBIUM-CONTAINING COMPOUND INTO HIGH PURITY TANTALUM AND NIOBIUM COMPOUNDS

摘要

A method for obtaining a high-purity tantalum compound and a high-purity niobium compound comprises: (a) dissolving a crude compound containing tantalum and niobium in hydrofluoric acid optionally with an inorganic acid, adjusting the resulting acidic aqueous solution to have a HF concentration not higher than 4 N, and contacting the acidic aqueous solution with a sparingly water-soluble organic solvent containing from 1.0 to 1.2 equivalents of a sparingly water-soluble quaternary ammonium compound per equivalent of the Ta in the aqueous solution, to selectively extract Ta in the aqueous solution in the organic solution; (b) adjusting the HF concentration of the Ni-containing aqueous solution from step (a) to from 0.5 to 5 N and contacting the aqueous solution with a sparingly water-soluble organic solvent containing from 1.0 to 2.0 equivalents of a sparingly water-soluble quaternary ammonium compound per equivalent of the Ni contained in the aqueous solution, to extract the Ni into the organic solution; (c) contacting the tantalum-containing organic solution obtained in (a) with an aqueous solution containing at least one inorganic acid and/or ammonium salt, and optionally HF, to remove impurities extracted concomitantly into the organic solution; and (d) contacting the Ni-containing organic solution obtained in (b) with an aqueous solution containing HF and optionally an inorganic acid and/or ammonium salt, to remove impurities extracted concomitantly into the organic solution. The method provides a Ta compound and Ni compound, particularly tantalum pentoxide and niobium pentoxide, having high purities (99.999% to 99.9999%) at high yields.