Sequential extraction of tungsten from scheelite through roasting and alkaline leaching

Extraction of tungsten from scheelite is important for the processing of tungsten resources for tungsten metallurgical companies. However, there are many difficulties to leach scheelite compared to wolframite. Compared with calcium tungstate (CaWO4), magnesium tungstate (MgWO4) is a readily soluble substance in NaOH solution. In this paper, conversion of CaWO4 to MgWO4 through roasting a mixture of scheelite and MgCl2 was investigated systematically. The leaching performance of the roasted products in NaOH solution was also studied. Thermodynamic analyses and experimental results showed that MgWO4 could be prepared through reaction of CaWO4 with MgCl2. Increasing roasting temperature and MgCl2 dosage could increase the extent of conversion of CaWO4 to MgWO4. Additionally, leaching experiments showed a good leachability of the roasted products with a tungsten leaching efficiency of 98.79% in 4 M NaOH solution at 90 degrees C. This work may provide an alternative approach for the extraction of tungsten from scheelite.