Fine tungsten trioxide can be prepared by double salt method with apparent density of 0.5~0.7g/cm3. Smaller the particle size, smaller the apparent density. Its specific production process is show as bellow:
Mix double salt and water. And pour 30% to 31% concentration of cold hydrochloric acid slowly into the slurry. At the beginning, colloidal tungstic acid with white amorphous appearance is formed. The white tungstic acid turns into yellow tungstic acid precipitate with the continuous increase of the hydrochloric acid, the gradual increase of acid concentration and the extension of reaction time. The mass ratio of the raw material is:
Double salt: deionized water: hydrochloric acid = 1: 0.5~0.95: 1.
It requires the hydrochloric acid must be poured into the double salt slurry. The temperature of the feed liquid is at the range of 42~58°C. The appropriate reaction time is between 15min and 20min. After washing, drying and calcining at the temperature range of 700~750 °C, the tungsten trioxide with fine granule is obtained.
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