Production of Ammonium Metatungstate

Metatungstate production methods more, can be divided into solid and liquid phase inversion transformation method two categories. Typical solid phase inversion process is based on the thermal degradation APT method as a raw material, this method is the main industrial production process of the AMT. The phase transformation method of ammonium tungstate solution as raw material, extraction, ion exchange, membrane electrolysis, or a method in the solution and the pH adjusted to the appropriate range, the obtained solution of ammonium metatungstate. Many research phase inversion method, is to develop in the direction of industrial applications.

Production of Thermal Degradation AMT

By controlling the APT and the pyrolysis temperature and the ammonia partial pressure of water vapor, the water-soluble pyrolysis APT metatungstate large amorphous material, and then hydrated into a solution of ammonium metatungstate, the solution was concentrated and cooling crystallization available AMT solid.

APT pyrolysis conversion rate and the temperature, if the pyrolysis temperature is too high, the resulting insoluble tungsten oxide is not, if the temperature is too low, the APT insufficient removal of ammonia and water (by Molecular Formula calculated APT be removed the four NH3 and 4 H2O), insolubles increases. APT suitable temperature to improve the conversion rate of the key.

Preparation of Ion-Exchange AMT

AMT ion exchange process to produce ammonium tungstate solution as raw material, ion exchange method because the process is relatively simple, easy to control, to avoid the formation of APT, not into the new contaminants, the process can be continuous, and thus has potential for development .

Extraction and ion exchange method originally buried in a similar, but in the extraction process is easy to produce solids resulting emulsion, industrial applications, there are certain difficulties. Silicic acid, and the solid is likewise prepared using ammonium tungstate solution, one way to take AMT, but due to the addition of silicic acid may cause contamination of the product AMT, so there is no industrial application. Ion-exchange membrane electrolysis (including ion-exchange membrane electrodialysis) is still in the development stage, to be developed better longer selective membrane, reduce production costs, to be applied to the production.


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