Direct Tungsten Extraction from Scheelite in a Molten Salt Media

Tungsten is a basic metal commodity that is classified as critical raw material (CRM) by the European Commission (EC) with the highest economical importance compared to other CRM.Thanks to its unique properties, secure W supply is critical to all industrial applications involving cutting or component wear, such as mining, machining, construction, tools and dies.Other important uses are in high-strength steels and high-temperature alloys, chemicals, mill products and lighting filaments.The production of W metal or carbide to be used in end products, requires a reduction process of the oxide which has been previously extracted from the primary (ores) resources by complex and energy intensive hydrometallurgical processes.In the frame of the EC-funded TARANTULA project (GA 821159), innovative methods to obtain W metal directly from scheelite raw material have been investigated.The process comprises two steps, i.e., selective chlorination of the W ore in a molten chloride media using gaseous reactants, and subsequent electrolysis of the dissolved W electroactive species from the same reaction media.The chlorination of natural scheelite in a molten chloride has been demonstrated in the equimolar NaCl-KCl mixture at a working temperature of 727 °C, using both Cl2(g) and HCl(g).The dissolved W species in the molten chloride were found to be tritungstate: W3O10 2-and/or the chloro-complex, as e.g., W3O10Cl2 4-.Subsequent electrolysis trials demonstrated the recovery of WC2 deposits on a carbonaceous cathode, while the anode reaction was evidenced to include the discharge of the oxide ions from the dissolved tritungstate species.