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.