Understanding the wet decomposition processes of tungsten ore: Phase, thermodynamics and kinetics

As a strategic rare metal, tungsten is widely used in high-performance metallic materials like cemented carbide. The wet decomposition of scheelite CaWO4 and wolframite (Fe,Mn)WO4 is the primary and important step in tungsten metallurgy. According to the phase separation behaviors of the decomposition products, the wet decomposition processes of tungsten ore MWO4 (M = Ca, Fe, Mn) are summarized into four categories: the processes of producing 1) soluble M and insoluble W, 2) soluble M and soluble W, 3) insoluble M and insoluble W, 4) insoluble M and soluble W, each of which can derive specific decomposition methods with distinct characteristics. In thermodynamics, the equilibrium constant vs. temperature diagrams, predominance-region diagrams and phase diagrams of different acidic or alkaline decomposition methods were calculated and compared. In kinetics, the rate-determining step and targeted process intensification are analyzed and discussed, especially the phase separation/transformation of tungsten ore and decomposition products. Finally, the wet decomposition processes of tungsten ore are evaluated with respect to four aspects: principle and practice, laboratory and plant, resources and environment, and cost and benefit. The alkaline processes represented by the classical NaOH decomposition method and the acidic processes represented by the state-of-the-art H2SO4-H3PO4 synergistic decomposition method will jointly promote the vigorous development of the tungsten metallurgical industry. [Display omitted] •A review based on the novel perspective of phase separation.•Summary and classification of the wet decomposition processes of tungsten ore.•Focus on the analysis and comparison in both thermodynamics and kinetics.•Viewpoints for connecting experimental research and industrial application.