Process of extracting and recovering columbium and tantalum from their ores and products thereof

摘要

Niobium and tantalum values are extracted and separately recovered from their ores, such as columbite or tantalite, which are preferably first ground and roasted between 600 DEG and 800 DEG C. to oxidize the iron and manganese, by digesting with an ammonium fluoride solution to yield complex ammonium-metal fluorides. The solution thus obtained may be freed from minor impurities by adding a soluble sodium salt, preferably the carbonate. The tantalum may be recovered from the solution as potassium fluotantalate by treating with a soluble potassium salt, preferably the fluoride, followed by cooling to 10 DEG C. to crystallize the potassium fluotantalate. The remainder of the tantalum may now be recovered by adding ammonia until the pH of the solution is 6.0 to 6.5, and warming the resulting slurry to about 90 DEG C. to redissolve the niobium. The tantalum is recovered as the hydrous oxide. By adding a large excess of ammonia to the solution niobium hydrate is precipitated and recovered. By dissolving this precipitate in a concentrated mineral acid other than hydrofluoric acid and boiling, an exceptionally pure niobium oxide is precipitated. The potassium fluotantalate may also be hydrolysed using ammonia to give tantalum oxide. The insoluble residue from the digestion with ammonium fluoride consists mainly of ferric and manganic ammonium fluorides. Ammonium fluoride can be recovered from these by slurrying with excess ammonia in the presence of a small quantity of an oxidizing agent such as hydrogen peroxide. Iron and manganese hydrous oxides are also obtained.