How to extract tungsten from wolframite/scheelite ores efficiently?

2025-11-02

Extracting tungsten from wolframite and scheelite, the major tungsten ores, involves physical, chemical, and sometimes biological processes. The key steps for efficient extraction are as follows:

1. Ore Beneficiation:

The extraction process begins with the concentration of tungsten from the base ore using physical separation techniques.

• Gravity Separation:Wolframite has a high specific gravity (~7.5 g/cm³), making it suitable for gravity methods such as jigging, shaking tables, and spiral separators. Scheelite has a lighter specific gravity (~6 g/cm³) but can also be separated using gravity-based approaches.

• Flotation:Scheelite is often floated using collectors like oleic acid or sodium oleate in combination with modifiers to ensure selectivity. Flotation is particularly effective for fine-grained ore.

• Magnetic Separation:Wolframite is highly magnetic, so it can be separated using strong magnetic fields. This step is effective in removing impurities or other minerals.

2. Chemical Conversion for Tungsten Extraction:

After concentrating the ore, chemical processes are used to extract tungsten.

• Alkaline Process for Scheelite:Scheelite ore is treated with sodium carbonate or sodium hydroxide solution at high temperatures (~200–400°C) to convert tungsten into soluble sodium tungstate:\[\text{CaWO}{4} + \text{Na}{2}\text{CO}{3} \rightarrow \text{Na}{2}\text{WO}{4} + \text{CaCO}{3}\]

  The sodium tungstate solution is filtered and purified through crystallization or ion-exchange to remove impurities such as molybdenum or phosphorus.

• Roasting and Leaching for Wolframite:Wolframite is roasted with soda ash or sodium nitrate at high temperatures to convert tungsten into soluble sodium tungstate:\[\text{FeWO}{4} + \text{Na}{2}\text{CO}{3} \rightarrow \text{Na}{2}\text{WO}{4} + \text{FeO} + \text{CO}{2}\]

  The roasted product is leached with water to dissolve the sodium tungstate. Impurities such as iron are removed via precipitation.

3. Tungsten Recovery:

From the sodium tungstate solution, tungsten is recovered in usable form.

• Purification:The sodium tungstate solution is treated with acid (e.g., hydrochloric acid or sulfuric acid) to precipitate tungsten trioxide (WO₃):\[\text{Na}{2}\text{WO}{4} + 2\text{HCl} \rightarrow \text{WO}{3} + 2\text{NaCl} + \text{H}{2}\text{O}\]

  Highly purified WO₃ is further reduced in hydrogen atmospheres to metallic tungsten:\[\text{WO}{3} + 3\text{H}{2} \rightarrow \text{W} + 3\text{H}_{2}\text{O}\]

4. Specialized Methods to Improve Efficiency (Optional):

If higher efficiency and purity are required, techniques like these might be applied:

• Solvent Extraction:Solvent extraction methods help to remove impurities and selectively recover tungsten when multiple elements are in solution.

• Ion Exchange:Ion exchange systems are used to capture tungsten ions and purify the liquid phase, yielding a higher purity product.

• Electrowinning:Some processes utilize electrochemical methods in conjunction with leaching to recover tungsten directly.

Overall, the specific operational parameters (e.g., temperature, pH, reactant concentrations) will vary depending on the ore composition and desired purity levels. Tailoring the beneficiation and extraction process is crucial to maximizing efficiency and minimizing environmental impact.

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