【Know Tungsten】Production Methods of Ammonium Paratungstate

1. Production methods of ammonium paratungstate include evaporation method, crystallization method, freeze-drying method and solvent extraction method.

2. Evaporation Method
Add hexamethylenetetramine to the ammonium tungstate solution, then adjust the pH to 5～2.0 with sulfuric acid, and the temperature cannot exceed 20℃. Then filter, dissolve the filtrate in ammonia water, and heat to evaporate.

3. Crystallization Method
Evaporate the solution in a constant temperature water bath at 50-70°C for 1 to 2 hours, then neutralize it with hydrochloric acid to a pH of 7.0-7.5, then evaporate to a mother liquor density of 1.08-1.109/ml, and finally discharge and cool.

4. Freeze-drying Method
Ammonium tungstate solution and liquid nitrogen are injected into an enameled dish containing liquid nitrogen in a ratio of 1:2～3 (volume), a little stirring is used to obtain a paste product, and it will be quickly moved together with the enameled dish to dry In the equipment, the product can be obtained by subliming and removing water under a certain degree of vacuum.

5. Solvent Extraction Method
During extraction, the pH of the ammonium tungstate feed solution should be greater than 9, and the concentration of W03 should be 100～2009/L. Mix the feed solution with the extractant EPA and shake to extract the ammonium ion from the feed solution to reduce the pH value of the feed solution. Then control the pH of the raffinate to 6-7. After standing for phase separation, digest the raffinate at 60°C for 5 hours to obtain the product with a crystallization rate as high as 96%.

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