A Process for Preparing Tungstic Trioxide of High Purity from a Canadian Scheelite Concentrate

CIM Bulletin1966
J. A. Vezina Senior Scientific Officer and W. A. Gow Heod, Extraction Metallurgy Division Hydrometallurgy Section, Mines Branch, Dept. of Mines & Technical Surveys, Ottawa, Ont.
A new process for treating scheelite for the production of tungstic trioxide is described. The novelty of the process resides in that an ion-exchanger is used to convert sodium tungstate to either ammonium tungstate or tungstic acid. The process consists of a conventional hydrochloric acid leach of the scheelite concentrate, and the dissolution of the impure tungstic acid thus produced with sodium hydroxide at pH 8. The sodium tungstate solution is clarified and passed through a column of Dowex 50Wx8 ion-exchange resin to exchange the sodium ions for either hydrogen or ammonium ions, both being suitable. The tungsten-bearing column effluent is evaporated to crystallize the tungsten as ammonium tungstate; the crystals are washed with nitric acid and water and decomposed by heat to produce tungstic trioxide of high purity. Ninety-six per cent of the tungsten in the concentrate may be recovered as tun gs tic trioxide (W03), and the reagents consumed are 0.7 g HCl, 0.41 g NaOH and either 1.73 g NH.Cl or 225 g HCl per gram of tungsten
Keywords: Acid, Concentrate, Concentrates, Hydrochloric acid, hydrochloric, Sodium Hydroxide ...... ., sodium tungstate, Table V-Leaching Scheelite Concentrate, tungstic acid, leaching, resin, resins, test, Tests, Tungsten
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