GB833241A - Process for separating niobium and tantalum from materials containing these metals - Google Patents

Abstract

A mixture of chlorides and/or oxychlorides of niobium and tantalum in solution in an anhydrous alcohol (preferably methanol) is treated with 8-oxyquinoline, the hydrochloric acid liberated during the dissolution of the chlorides in the alcohol being at least partially neutralized, thereby preferentially precipitating niobium oxyquinolate, from which the oxide may be recovered. The 8-oxyquinoline may either be added alone or dissolved in a suitable solvent, such as an ether, ester, or ketone, but preferably in the same alcohol as the chlorides. The hydrochloric acid may be neutralized before, during, or after the reaction with the 8-oxyquinoline, preferably with a weak base such as quinoline, aniline, mono- or diethylaniline, dimethylaniline, 2-methyl-5-ethylpyridine, but especially pyridine, in which case excess base may be added. When a strong base is employed, to ensure preferential precipitation, only sufficient to neutralize 70-90% of the acid should be added. The tantalum oxyquinolate may then be precipitated by further neutralization. The 8-oxyquinoline can be recovered from the precipitates by boiling with 50% sulphuric acid, diluting to 5%, heating for several hours, separating the precipitated metal oxide, and neutralizing the liquor to precipitate the 8-oxyquinoline. Excess 8-oxyquinoline may be recovered from the exhausted original alcoholic solution by neutralization to precipitate the 8-oxyquinoline. The mixture of chlorides and/or oxychlorides to be separated may be obtained by the chlorination of material, especially oxides and alloys, containing niobium and tantalum, with chlorine gas in the presence of carbon. The oxychlorides initially formed may be further chlorinated to the pentachlorides. Alternatively the oxides may be heated in a current of dry carbon tetrachloride. In an example, a mixture prepared as above is dissolved in methanol, boiled, mixed with HCl, heated, diluted with water, and 50% H2SO4 added to precipitate the hydrated oxides of niobium and tantalum, which precipitate was removed, boiled with dilute HCl and H2SO4, calcined, and chlorinated to give the starting chloride mixture.ALSO:A mixture of chlorides and/or oxychlorides of niobium and tantalum in solution in an anhydous alcohol (preferably methanol) is treated with 8-oxyquinoline, the hydrochloric acid liberated during the dissolution of the chlorides in the alcohol being at least partially neutralized, thereby preferentially precipitating niobium oxyquinolate. The 8-oxyquinoline may either be added alone or dissolved in a suitable solvent, such as an ether, ester or ketone, but preferably in the same alcohol as the chlorides. The hydrochloric acid may be neutralized before, during, or after the reaction with 8-oxyquinoline, preferably with a weak base such as quinoline, aniline, mono- or diethylaniline, dimethylaniline, 2 - methyl - 5 - ethylpyridine, and especially pyridine, in which case excess base may be added. When a strong base is employed only sufficient to neutralize 70-90% of the liberated hydrochloric acid should be added to ensure preferential precipitation. The tantalum oxyquinolate may then be precipitated by further neutralization. The 8-oxyquinoline may be recovered from the precipitates by boiling with 50% sulphuric acid, diluting to 5%, heating for several hours, separating the precipitated metal oxide and neutralizing the liquid to precipitate the 8-oxyquinoline. Excess 8-oxyquinoline may be recovered from the exhausted original alcoholic solution by neutralization to precipitate the 8-oxyquinoline.