| 摘要 |
A process is provided for extracting tungsten values from tungsten compositions. The process comprises treating a tri (alkaline earth metal) tungstate, especially tricalcium tungstate, at a temperature of preferably no greater than 50 DEG C. with a aqueous solution of hydrochloric and/or nitric acid, preferably having a concentration of no greater than 5 molar. The acid is supplied in excess of te stoichiometric amount required to convert the tungstate to tungstic acid and sufficient to maintain the thusly formed tungstic acid insoluble in the solution. The tungstic acid can then be separated from the solution and converted to soluble ammonium tungstate, which in turn can be converted into tungsten trioxide and finally into metallic tungsten. The tri (alkaline earth metal) tungstate starting material can be prepared from iron tungstate, manganese tungstate, and/or an alkaline earth metal tungstate or from ores or concentrates of these tungstates, by a high temperature treatment with calcium oxide. The tungsten values can be obtained with good yields and low levels of impurities.
|
