Electrodialysis Method Producing Ammonium Paratungstate

Electrodialysis method to prepare ammonium paratungstate (APT) is a way to produce high purity APT, using electricity instead of chemical reagents, and a process which meets the requirements of both economic and environmental protection. Decomposing sodium tungstate (Na₂WO₄) to sodium hydroxide (NaOH) and multi tungstic acid by electrodialysis method is the in the most important step in producing ammonium paratungstate, thus can recover and reuse sodium ions (Na⁺) in any concentration of NaOH solution.

Processes of electrodialysis method producing ammonium paratungstate (APT) are as follows:
1. Leach out and dissolve waste tungsten or tungsten concentrate to get sodium tungstate solution (Na₂WO₄);
2. The Na₂WO₄ solution is carried out electrodialysis to get sodium hydroxide (NaOH) and multi tungstic acid;
3. Acidize and solvent extract the multi tungstic acid complex, and then separate with water in the clarify chamber;
4. Add ammonia water to reextract tungsten complex into aqueous solution, and then crystallize APT.