Hydrometallurgy of Tungsten from Primary Ores and Secondary Sources: Mineralogical Controls, Selective Recovery, Process Integration, and Sustainability—A Critical Review

Tungsten extraction involves a technically heterogeneous portfolio of scheelite, wolframite, mine wastes, cemented-carbide scrap, spent catalysts, and process residues. This critical review evaluates how feed mineralogy, aqueous speciation, reaction pathways, separation selectivity, and process integration control the conversion of these materials into marketable tungsten intermediates, notably ammonium paratungstate (APT). Literature assembled through 17 route-specific Boolean search strategies for 2020–2026, with selected expansion to 2010–2019, is appraised by feedstock, mechanism, impurity behavior, technological evidence, and environmental relevance. The synthesis identifies structural differences between alkaline digestion of wolframite, chemically assisted decomposition of scheelite, and secondary-material processing in which cobalt, vanadium, molybdenum, arsenic, and titanium influence the preferred flowsheet. In solution purification, W–Mo separation and changing polytungstate chemistry require explicit control of solution composition rather than generic extraction performance claims. Closed-loop reagent management, full metal balances, impurity deportment, product purity, residue stability, and pilot-scale demonstration remain essential but are reported inconsistently. This review proposes a process-selection framework that integrates mineralogical qualification, thermodynamic–kinetic interpretation, evidence-based separation screening, and coupled technical, economic, and environmental assessment. The review distinguishes established process principles from promising laboratory innovations and identifies minimum evidence needed before industrial extrapolation