Ultrasonic microwave hydrothermal method to prepare ammonium paratungstate (APT) is the way of combining both energies of ultrasonic wave and microwave and changing into sodium tungstate [(NH4)2WO4] heat, and then producing ammonium paratungstate by hydrothermal method. Due to the limitation of raw material, equipment, process flow and other factors, this method is generally suitable for laboratories and research institutions, and does not used for APT industrialized production. In particular, because of the small selection range of raw material, ultrasonic and microwave hydrothermal method is more suitable for in the production of high purity APT.
The equipments of ultrasonic microwave hydrothermal preparation of ammonium paratungstate include magnetic stirrer, microwave generator, ultrasonic generator, three flask, temperature sensor, etc., with the process as following:
1. Place the ammonium tungstate solution which has the tungsten trioxide (WO3) with concentration no less than 220 g/l in three flask, open the magnetic stirrer to stir the solution with a ceratin speed;
2. Heat the ammonium tungstate solution by opening the microwave generator and ultrasonic generator with a fixed power, and controlling the different microwave, ultrasonic wave frequency;
3. Control the temperature of reactant solution at above 80℃ after APT begin to crystallize;
4. Control the crystallization rate within 65%, to obtain high purity products of ammonium paratungstate.