Ammonium Paratungstate Preparation Method
Ammonium paratungstate (APT) preparation is an important part of smelting tungsten, whether it is using chemical precipitation method, ion exchange method or extraction method, it all have to go through the process of ammonium trioxide to produce qualified APT.
APT is an important tungsten intermediate product, the higher the purity the greater the value, so APT preparation process is also the further purification of tungsten.
Commonly used method for preparing ammonium paratungstate is evaporation crystallization method, neutralization crystallization method and frozen crystallization method.
Evaporation crystallization method is heating evaporation solvent, so that the solution from unsaturated to saturated, continue to evaporate, the excess solute will be crystal precipitation, called evaporation crystallization method. This method of technology and equipment is simple, easy to large-scale, this method technology and equipment is simple, easy to large-scale, at the same time it has a purification effect, so it’s universal.
And the crystallization is at room temperature neutralizing (NH4)2WO4 solution with hydrochloric acid, dissolving out the ammonium paratungstate crystals.This method has small energy consumption, fast crystallization, and easy to recycle fine particles APT.
Frozen Crystallization In water-cooled vacuum drying, water and APT crystallize at the same time, but then remove the water and leave the dry APT. The advantage of this method is that it can produce ultrafine powder and obtain a homogeneous composite powder.
In addition to the above three common methods, the industry also uses other methods to produce high purity ammonium paratungstate, such as neutralization - evaporation crystallization, extraction, recrystallization, electrolysis. There are many methods and they all have their own merit and demerit. In conclusion, In addition, the main problems of the preparation of ammonium paratungstate crystals are the removal and control of the crystalline morphology to meet the needs of the final tungsten product as the standard.
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