Coarse ammonium paratungstate has advantages of large apparent density and good fluidity, and its demand increases year by year as customers are requiring more and more strictly on the performance of subsequent products now.
Preparation of Coarse Ammonium Paratungstate
1. Experimental solution and equipment:
(1) Adopt (NH4)2WO4 solutions produced by classical process and ion exchange process as test material liquid; Part of the solution was prepared by diluting ammonia water.
(2) A 1500L open type enamel reactor equipped with an anchor stirrer, an exhaust device, and a mercury thermometer (with a precision of 0.03°C) is used as a crystallizer.
2. Experimental procedures:
(1) After washing the reactor with pure water, a certain amount of test solution was infused.
(2) The temperature of crystallization process was varied by adjusting the vapor pressure of the reactor jacket (control accuracy of ± 0.5x104 Pa).
(3) Record readings of mercury thermometer during a certain period of time and quickly sample the solutions to determine its density. Record the boiling point and temperature at which nucleation is formed.
The density of APT at crystallization end point was 4.7±0.1 Baume.
(4) The crystalline APT was washed by filtration and dried in the far-infrared at 100°C.
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