GB1089913A - Recovery of tungsten values from ores - Google Patents

Abstract

Tungsten values are recovered from powdered schulite and/or wolframite type ores by: (i) fuzing preferably at 698-825 DEG C. with a mixture of sodium chloride and sodium carbonate, which also contains siliceous material (e.g. silica) if calcium is present and may also contain sodium nitrate, (ii) leaching with water, (iii) separating the tungsten-bearing alkaline liquor from water-insoluble impurities, (iv) preferably, an alkali metal sulphide, e.g. Na2S, NaHS is then added to precipitate antimony and arsenic sulphides, after acidification to pH 4.0 to 5.6 and molybdenum sulphide after further acidification to pH < 4, (v) adding a fluoride or hydrofluoric acid to form water-soluble compounds which are insoluble in organic media with any phosphorus or silicon, preferably sufficient to give 6 molecules of fluorine for every molecule of P and Si, (vi) extracting with an organic solution of an amine capable of forming a water-insoluble organic amine-tungsten complex, e.g. tertiary tridecyl, triamyl, tri-isooctyl or trilauryl amine in a ketone or paraffinic diluent and separating, (vii) treating the organic phase with aqueous ammonia to form a water-soluble ammonium tungstate, preferably sufficient to raise the pH to \sF 7.5, and separating. The tungsten-bearing aqueous solution may then be evaporated to give ammonium paratungstate crystals, and the ammonia vapour recycled to step (vii). The organic phase may be recycled to (vi) after-treatment with sulphuric or nitric acid, which itself may be recycled to step (iv). Reference has been directed by the Comptroller to Specifications 895,402 and 1,013,364.