From a Scheelite Concentrate (Spanish Origin) to Nanotungsten Derivatives

Tungsten is a series of metals considered strategic by the European Union, so there is great interest in its recovery from both raw materials and secondary products. Within these raw materials, there are cassiterite deposits containing tungsten. It is from one of these deposits (located in the northwest of Spain) that after electrostatic separation, a scheelite concentrate (4.8% tungsten) has been obtained. This concentrate has been processed through two hydrometallurgical procedures. In one case, alkaline leaching in sodium carbonate medium is used to obtain sodium tungstate solutions, which in turn allows synthetic scheelite (calcium tungstate) or tungstic acid to be obtained. The second procedure, which uses acidic leaching (hydrochloric acid medium), yields tungstic acid as the final product. In all of the above cases, the experimental conditions to yield the best tungsten recovery rates are defined. The different products (sodium tungstate solutions and tungstic acid) afforded were used as precursors to yield synthetic scheelite and nanotungsten compounds as amorphous meta- and paratungstate salts and non-stoichiometric tungsten blue oxides.