The Smelting Method of Tantalum
Tantalum-niobium ore is often accompanied by a variety of metals. The main steps of tantalum smelting are to decompose the concentrate, purify and separate tantalum and niobium, to prepare pure compounds of tantalum and niobium, and finally to prepare metal.
Ores can be decomposed by hydrofluoric acid decomposition method, sodium hydroxide melting method and chlorination method. Tantalum and niobium can be separated by solvent extraction (the commonly used extractants are methyl isobutyl ketone (MIBK), tributyl phosphate (TBP), sec-octanol and acetamide, etc.], fractional crystallization and ion exchange.
Separation: First, the concentrate of tantalum-niobite is decomposed with hydrofluoric acid and sulfuric acid to form tantalum and niobium into fluorotantalic acid and fluoroniobium acid, which are dissolved in the leaching solution. In the leachate, a strong acid solution with complex composition is formed. The tantalum and niobium leaching solution is extracted with methyl isobutyl ketone to extract tantalum and niobium into the organic phase at the same time, and the trace impurities in the organic phase are washed with sulfuric acid solution to obtain a pure organic phase washing liquid containing tantalum and niobium, and the raffinate is combined, which contains Trace amounts of tantalum, niobium and impurity elements are strong acid solutions and can be comprehensively recovered. The pure tantalum-niobium-containing organic phase is stripped of niobium with a dilute sulfuric acid solution to obtain a tantalum-containing organic phase. Niobium and a small amount of tantalum enter the aqueous phase and then extract the tantalum with methyl isobutyl ketone to obtain a pure niobium-containing solution. The pure tantalum-containing organic phase is back-extracted with water to obtain a pure tantalum-containing solution. The organic phase after stripping the tantalum is returned to the extraction and recycled. Pure fluorotantalic acid solution or pure fluoroniobium acid solution react with potassium fluoride or potassium chloride to form potassium fluorotantalate (K₂TaF₇) and potassium fluoroniobate (K₂NbF₇) crystals, and can also react with ammonium hydroxide to generate hydrogen Tantalum oxide or niobium hydroxide precipitates. The hydroxide of tantalum or niobium is calcined at 900~1000℃ to form oxide of tantalum or niobium.
