Leaching of synthetic scheelite by hydrochloric acid without the formation of tungstic acid

The kinetics of the leaching reaction of synthetic scheelite with hydrochloric acid was studied to determine the effect of pH and temperature in the formation of tungstic acid. Conversion data obtained from leaching in a temperature range of 28–100 °C and pH between 1.5 and 3.0 are interpreted in terms of the predominating tungsten species present in the leaching liquors. The results show that it is possible to digest the synthetic scheelite in the acidic hydrochloric medium without the formation of tungstic acid by monitoring and controlling the pH, and controlling the temperature in the domain of metatungstates. In this case, the experimental results match with the shrinking core model, and show that the solids leaching is kinetically under both chemical and mass transfer control.