Acid leaching of scheelite concentrates

The acid leaching in hydrochloric media of a tungsten concentrate (scheelite, CaWO4) was studied. Of the above-mentioned, an insoluble solid (H2WO4) was obtained which were treated with an alkaline solution of sodium hydroxide, achieving the complete solubilization of the tungsten as wolframate ion (WO4-2). The transformed fraction of tungsten increases with the temperature, as well as with a finer grain. A maximum dissolution of 88.5% (400 g/l HCl, 363 K and 20 mu m of particle size) was achieved for a 3 h process, of the disolution process was interpreted by the recessive core model with formation of a layer of solid product for the whole range of variation of the parameters in study. The activation energy value was found to be 28.0 kJ/mol.