How to Recover Tungsten from Mixed Wolframite-Scheelite Ores Efficiently?

2026-01-06

Recovering tungsten efficiently from mixed wolframite-scheelite ores requires a combination of physical and chemical separation techniques tailored to exploit the distinct properties of both minerals. Here is a systematic approach:

1. Mineral Characterization

• Conduct a detailed study of ore composition using techniques like X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM).
• Determine the proportion of wolframite \[(Fe,Mn)WO4\] and scheelite (CaWO4), as well as the presence of impurities (e.g., sulfides, silicates).

2. Physical Beneficiation

• Comminution (Grinding): Carefully grind the ore to liberate wolframite and scheelite particles from impurities without over-grinding.
• Gravity Separation: Since wolframite and scheelite are both dense minerals, gravity separation techniques like jigging or shaking tables can be used to separate them from lighter gangue minerals.
• Magnetic Separation: Exploit the magnetic properties of wolframite, which is strongly magnetic, to separate it from scheelite, which is non-magnetic. High-intensity magnetic separators work well for this purpose.
• Flotation for Scheelite: If scheelite is mixed with gangue or cannot be separated by gravity or magnetic methods, flotation techniques using selective reagents (e.g., fatty acids) can recover scheelite.

3. Chemical Methods

• If physical methods cannot achieve sufficient separation, combination processes involving chemical treatment may be employed.
• Hydrometallurgy: Leach scheelite using acid or alkaline solutions (e.g., NaOH or HCl) while avoiding the dissolution of wolframite. Scheelite is soluble in strong acids, whereas wolframite is more resistant.
• Roasting: Roasting may be employed to enhance selective extraction by altering mineral properties.

4. Optimization of Reagents

• For flotation, optimize reagents like collectors, modifiers, and depressants specific to scheelite. Examples include sodium silicate to depress gangue and fatty acids for scheelite collection.
• Study the effect of temperature, pH, and reagent concentration on the flotation and overall recovery efficiency.

5. Combination Processes

• Sometimes, a combination of physical and chemical processes is required for the efficient recovery of both wolframite and scheelite. For instance:
  • Gravity separation followed by magnetic separation for wolframite.
  • Flotation for scheelite.

6. Tailings Management

• Evaluate the tailings after each step for remaining tungsten content. Reprocess if economically viable using finer grinding, additional flotation, or other techniques.

7. Environmental and Economic Considerations

• Minimize the use of toxic reagents for environmental safety.
• Opt for energy-efficient processes to reduce costs.
• Ensure compliance with local regulations regarding effluent discharge and waste management.

Example Flowsheet

1. Grinding → Gravity separation (wolframite recovery) → Magnetic separation (wolframite refinement).
2. Tailings → Flotation (scheelite recovery).

Both minerals can ultimately be converted into usable tungsten products (e.g., tungsten trioxide or ammonium paratungstate) via chemical processing in later stages, once they are separated.

Each step needs adjustment depending on the ore’s specific properties. Conduct pilot-scale tests to refine the process before full-scale implementation.

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