Acid leaching of scheelite concentrates

Abstract

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/1 HCl, 363 K and 20 µm 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