Ammonium Paratungstate Producing Method

Ammonium paratungstate producing method includes evaporation crystal method, neutralization crystal method and lyophilization crystal method.

Evaporation crystal method is the most widely applied in industry. Reduction evaporation is common used in the producing process. Vacuum pressure is maintained around 40kpa, evaporation temperature is between 353-363k, producing the strip of crystallization and the component of which is 5(NH4)2O•12WO3•5H2O3.

Neutralization crystal method neutralizes hydrochloric acid with concentration of 10%-20% and ammonium tungstate solution to ph value 7. If neutralizing acid under temperature 363-368k, after an hour ammonium paratungstate is produced by crystallization. If adding acid under room temperature, the solution needs to be stewing for 8-12 hours, sometimes even 24 hours, the finished ammonium paratungstate is of shape like needle and the component of which is 5(NH4)2O•12WO3•11H2O.

Lyophilization crystal method freezes ammonium tungstate solution first and heat it under vacuum low pressure environment which can obtain polyporous and drying ammonium paratungstate.


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