Multielement selective separation and extraction in hydrometallurgical processing of complex zinc resources

The increasing use of low-grade, refractory, polymetallic and secondary zinc resources is fundamentally changing the separation requirements of zinc hydrometallurgy. At the same time, intensified leaching, through higher temperatures and acidities or oxygen-pressure operation, enhances refractory-phase decomposition but may also increase the transfer of Fe and associated elements into solution, thereby raising the downstream separation burden. This review critically examines how these two trends affect multielement distribution and downstream selective separation throughout zinc hydrometallurgical flowsheets, while also summarizing recent adaptive developments. Intensified leaching is shown to shift the principal challenge from Zn dissolution to the selective removal of Fe, Cu, Cd, Co and Ni from concentrated ZnSO 4 solutions. Zinc-dust cementation and its interfacial intensification are assessed for trace-impurity removal, whereas jarosite, goethite, hematite and magnetite precipitation are compared as Zn Fe separation routes. Electrowinning requirements are further used to define the necessary control of metallic impurities, halides, organics, Mg and Mn. The recovery of In, Ge, Ga and Ag and the removal or recovery of Tl are evaluated according to their distribution among leach liquors, purification residues, iron precipitates, dust and final residues. The evaluation indicates that maximizing Zn extraction alone may increase downstream purification loads and disperse associated elements into low-grade or hazardous streams. Future developments should therefore couple leaching intensity with purification capacity, iron-residue regulation, electrowinning requirements and stream-specific recovery of associated elements. Their evaluation should also account for resource inputs, secondary-stream generation and industrial feasibility. Particular priorities include validation using increasingly complex industrial zinc-process liquors, selective enrichment during impurity removal, production of reusable iron-rich products and controlled bleed streams for hazardous-element removal.