Ammonium tungstate, ammonium paratungstate, ammonium metatungstate or hydrated tungsten trioxide is produced by passing tungstate anions through an anion exchange membrane into an aqueous solution containing ammonium cations under the driving force of an electrical potential for a time sufficient to achieve a pH within the range in which the desired tungsten compound will form.

 

In accordance with the invention a method has been discovered for manufacturing ammonium tungstate, ammonium paratungstate, ammonium metatungstate and tungstic acid requiring only ammonium hydroxide or other source of ammonium cations and a tungstate anion source as raw materials. These tungsten compounds can be manufactured in accordance with the invention without the production of useless byproducts and without the use of strong mineral acids, solvent extraction or precipitation reactions.

 

These tungsten compounds can all be produced in good yield and relatively free from cation impurities by passing tungstate anions under the influence of an electrical potential through an anion exchange membrane into an aqueous electrolyte containing ammonium cations until the desired pH of the electrolyte is reached for formation of the desired tungsten compound.

 

In another aspect of the invention, ammonium metatungstate or tungstic acid may be produced from normally insoluble ammonium paratungstate by using ammonium paratungstate crystals as the source of tungsten anions.

 

In another aspect of the invention, the alkali metal hydroxide formed by the removal of tungstate ions from alkali metal tungstate solution may be recovered and used to form additional alkali metal tungstates from tungsten sources such as ore concentrates.