The Extraction of Niobium and Tantalum from Columbite by the Nitrofluor Process

The Nitrofluor process provides a through method of dissolving the columbite in a nonaqueous inorganic solvent, purifying the niobium and tantalum, and separating them each other by volatile separation techniques. HF solutions of N_2O_3, N_2O_4 or NOF can disintegrate the columbite even at a room temperature. Subsequently, most of the niobium and tantalum precipitate as complex fluorides, leaving in the solution relatively large quantities of impurities, such as iron, manganese, titanium and tin. For further isolation of the complex fluorides of niobium and tantalum from the impurities, a volatilization of the niobium and tantalum from the dissolver solid separated from the dissolver solution is found effective. There appears to be a possibility of separating niobium and tantalum from each other by fractional sublimation utilizing the difference of volatility of these complex fluorides when the HF-N_2O_3 azeotrope is used for disintegrating the columbite. A general flowsheet for treating typical columbite or tantalite by the Nitrofluor process is proposed