CAUSTIC FUSION OF COLUMBITE-TANTALITE CONCENTRATES WITH SUBSEQUENT SEPARATION OF NIOBIUM AND TANTALUM

Abstract

A procedure for the production of spectrographically pure niobium and tantalum oxides from ooli.unbite-tantalite . concentrates was developed in this study. The procedure involves a caustic fusion process and the separation of tantalum and niobium by liquid-liquid extraction. The finely ground ore is fused with sodium hydroxide. The fused material is cooled and washed with cold water to remove most of the tin, silicon, and aluminum and part of the manganese. The reddish residue is made into a thick slurry by adding a small amount of water and stirring. Diluted sulfuric acid (1:1) and iron powder are added to aid in dissolving the manganese; then more water is added to bring the sulfuric acid to about 1 molar. The insoluble residue which contains the niobic and tantalic acids is recovered by filtration. It is washed and then dried at about 200 degrees Centigrade. The dried residue which contains 5-10 per cent impurities is dissolved in a minimum amount of 70 per cent hydrofluoric acid. Tantalum and niobium are extracted from the aqueous hydrofluoric acid solution by the addition of an immiscible organic solvent, leaving most of the impurities in the aqueous phase. By washing the separated organic with portions of a dilu~e sulfuric acid solution, niobium with a small percentage of tantalum is removed from the organic. A small amount of niobium then remains in the tantalum-rich organic phase. Pure niobium oxide was obtained * This report is based on an M.S. thesis by James A. Pierret, submitted August, 1956,to Iowa State College, Ames, Iowa. This work was done under contract with the Atomic Energy Commission.