High Purity Tungsten Trioxide Preparation

The resources of China's tungsten ore are very rich, however, the reserves and production of high grade, easy exploitation of black, white tungsten ore declining sharply because of years of exploitation. So far, high-purity tungsten is also largely depended on imports. High-purity tungsten trioxide powders are indispensable raw materials in the electronics industry .It has been widely used in magnetron sputtering and large-scale integrated circuits. It can be used as a raw material made of metal tungsten, carbide manufacturing, cutting tools, molds and pull tungsten wire, it can also be used for powder metallurgy, it can be used for X-ray screens and fireproof fabrics, as well as coloring agents. Therefore, the preparation of high purity tungsten trioxide becomes an important research.

The Experimental Method:
The raw materials of tungsten trioxide are based on superior grade ammonium (APT) by calcination processes. The outputs of the original high-purity tungsten powder, including molybdenum 40mg / kg, iron 20mg / kg, about 95% tungsten powder. The preparation of high concentrations of hydrochloric acid and hydrogen peroxide is based on nitric acid ammonium paratungstate, which can produce high-purity tungsten powder, including molybdenum that containing 4mg / kg, iron 1mg / kg, tungsten ≥99%.

The Experimental Results:
1. When the solution that adding WHO₃ was boiled in the experiment, there are a large amount of bubbles during the precipitation, which plays the role of loosing tungstate, eliminating the artificial stirring, which is more obvious than plusing H₂O₂.
2. The precipitation of tungstate from paratungstate in high acidity (HCl> 8 mol / L), which can significantly reduce the quality of hetero-containing.
3. In the hydrolysis process of paratungstate acid, adding hydrogen peroxide (H₂O₂ ,100ml/kg) and nitric acid (the amount of hydrochloric acid 1/10), which can reduce the impurity content.
4. There is a difference of dissolve between a large number of H₂NO₄ and a very small amount of H₂MO₄, and H2WO₄ is completely precipitated, H₂MO₄ is dissolved in the high acidity (hydrochloric acid or nitric acid), which achieves separation.

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