A review of flowsheets for tungsten recovery from scheelite, wolframite and secondary resources and challenges for sustainable production

Tungsten finds numerous industrial applications owing to its excellent physicochemical properties and applications in high-tech material production, which make tungsten containing ores, minerals and scrap material strategic raw materials/resources. Tungsten extractive metallurgy (TEM) is a vital process in the tungsten industry for producing diverse high-purity products from raw tungsten-containing minerals. This paper systematically reviews the flowsheets of TEM processes and related sustainability challenges, providing valuable insights and establishing guidelines for making these processes more eco-friendly and economically viable. Classical early-stage TEM processes primarily rely on the decomposition of scheelite (CaWO4) by HCl and feature lengthy procedures, low WO3 recoveries, and a high reagent consumption. In comparison, recently developed flowsheets combine NaOH/soda high-pressure digestion and solvent extraction/ion exchange which offer several advantages: (i) high raw material adaptability, (ii) high tungsten utilization efficiency, (iii) high product quality, and (iv) operation simplicity. However, recently developed flowsheets exhibit several drawbacks: (i) high reagent consumption, (ii) discharge of large volumes of high-salinity wastewater, and (iii) production of alkaline leach residues classified as hazardous solid waste. Although recent developments have partially addressed the issues of wastewater and residue discharge, further research is required to assess the economic viability of these processes and their adaptability to raw materials. A sustainable TEM process requires the consideration of both practicality and eco-friendliness in the flowsheets, including the following: (i) adaptability to the growing complexity of raw materials, (ii) tungsten utilization efficiency, (iii) solution recycling, and (iv) comprehensive utilization of other valuable components. This study aims to provide insights into TEM flowsheets and establish guidelines for the development of environmentally friendly and economical processes.