Purification of Unqualified Ammonium Paratungstate

A method of using unqualified, waste and dirty ammonium paratungstate (APT) as raw materials to generate high purity APT is presented in this paper.

The method includes steps as following:
1. Calcining materials (unqualified, waste and dirty APT) to obtain tungsten trioxide;
2. Dissolving tungsten trioxide generated in ammonia to form ammonium tungstate solution;
3. Filtering ammonium tungstate solution generated, remove the solid impurities, and then evaporate and crystallize to get wet APT;
4. Drying and screening the wet APT crystal to obtain high purity APT with total content of impurities in less than 65ppm.

Characteristic of this method:
1. Using the general and unqualified APT to produce high purity APT is a purification process;
2. High purity APT will meet the follow-up APT deep processing to the production of high quality tungsten products;
3. Through the method of roasting APT to get tungsten trioxide and then dissolved in ammonia can impactful solve the problem of bed effect on apt direct dissolve in ammonia;
4. Part of impurities that difficult to remove is removed in the APT calcination process, and create the conditions for the production of high purity APT products;
5. Solve the practice that low quality of APT back to the main process by alkali dissolution, and improve the recovery rate of production process, reduces cost, and produce high purity APT products at the same time.

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