How to prepare high-purity ammonium paratungstate? The researchers proposed a method for preparing high-purity APT. This method improves the quality of ammonium paratungstate and reduces the production cost of high-purity APT.
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A Preparation Method of High-purity Ammonium Paratungstate
Step One: Put APT into the feed bin and send it into the rotary furnace through the screw feeder at a constant speed. Control the calcination temperature and atmosphere in the rotary furnace. The feed volume is 150 kg/h. The calcination temperature is 550 °C in the first zone, 640 °C in the second zone, and 680 °C in the third zone, respectively. After calcining, the conversion rate of APT to tungsten trioxide reached 98.85%.
Step Two: Control the temperature of the 150 g/L ammonia solution at 95 °C, and the liquid-solid ratio at 3:1 ml/g. Tungsten trioxide is added into the solution while stirring, and reacted for 1.5h to obtain an ammonium tungstate solution, and then filtered.
Step Three: After filtering the ammonium tungstate solution, measure it into an evaporative crystallization pot for evaporative crystallization, control the evaporative crystallization steam at 1-4 kgf/cm2, when the specific gravity of the solution is close to 1.05 g/cm3, stop heating, and separate the crystal and mother liquor to obtain aqueous ammonium paratungstate.
Step Four: Remove excess water in aqueous ammonium paratungstate by steam drying to obtain high purity ammonium paratungstate.
