Process for the manufacture of ammonium and alkali metal tungstates

Abstract From the Canadian patent

A process for the manufacture of a tungstate salt especially ammonium tungstate, is disclosed. In the process finely divided metallic tungsten and/or intermetalic iron/ tungsten species are contacted with an aqueous solution of a compound having a cation selected from the ammonium ion and/or alkali metal cations, and at least one anion selected from hydroxide, carbonate, bicarbonate, oxalate and phosphate. The aqueous solution also contains an oxidizing agent e.g. oxygen, hydrogen peroxide and peroxides of alkali metals. The process is carried out in the substantial absence of alkaline earth metals. The process may be used in the separation of tungsten from the wolframite ores.