Effect of Additional Acid on Ammonium Paratungstate Production
- Details
- Category: Tungsten Information
- Published on Wednesday, 30 December 2015 18:09
Ammonium paratungstate (APT) is an important intermediate product of the production of tungsten metal powder. To ensure the quality of tungsten powder, the average particle size, particle size distribution and crystal morphology should also meet certain requirements while the APT chemical purity does. With the rapid development of modern science and technology, there’re more and more demands for different grain size and shape of tungsten powder production, and thus the requirements of raw material APT are also getting higher and higher.
For APT crystallization conditions, the scholars have carried out extensive exploration and discussion, but the overall reports are rare, and the results are not entirely consistent. In order to investigate the basic conditions of APT production, for the preparation of APT crystallization problems, this article attempts to make some analysis and discussion on theory and the process practice based on a number of experimental studies made recently and some views are put forward by reference.
Effect of additional acid
Adjust the ratio of (NH4)2O and WO3 with hydrochloric acid solution, so that ammonium tungstate with high solubility can quickly transform into ammonium paratungstate with low solubility, resulting in a high oversaturation in favor of fine grain formation. After fine grain formation, crystal size can be controlled by controlling the temperature and time of evaporation and crystallization.
In the test , firstly, solution was heated and evaporated under constant stirring to more trickle slowly adding 10% to 20% hydrochloric acid to PH6.5 ~ 7.5. Test results shown in Figure 4. Figure 4 shows that the temperature rises APT bulk density increases, acid increases, the bulk density decreases; the thicker the longer reaction time after the addition of acid particles APT. Obtained by this method APT, crystalline rules, particle size is relatively concentrated, especially in the preparation of fine particles of APT more convenient. Test was observed, when the acid dosage reaches a certain level, tungsten acid appears.
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