A novel process for tungsten hydrometallurgy based on direct solvent extraction in alkaline medium

Abstract

The principle, flow sheet and characteristics of a novel process for tungsten hydrometallurgy based on direct solvent extraction (DSX) with quaternary ammonium salt in alkaline medium were introduced. The pilot tests and industrial tests of the direct solvent extraction process were conducted. The results indicated that, the new technology had excellent adaptability for the treatment of leach solutions from not only autoclave-soda leaching but also caustic soda leaching with different tungsten ores. When proper operational conditions were controlled, the impurities of P, As, Si could almost be removed while sodium tungstate (Na2WO4) solution transformed to ammonium tungstate (NH4)2WO4 solution in the DSX process. The concentration of WO3 in strip liquor could be up to around 170g/L. The raffinate could be returned to leaching step directly or after causticization by lime, the water and alkali could be recycled. Comparing with traditional process, the novel process shows the advantage of higher recovery of WO3, lower consumption of chemicals, and discharge of waste water. Based on pilot tests and industrial tests, an engineering demonstration line of the novel process for treatment of scheelite concentrate had been constructed and ran for more than 1year.