Jarosite Formation as an Iron-Precipitation Route in Hydrometallurgy: Process Chemistry, Kinetics, Impurity Deportment, Solid–Liquid Separation, and Residue Sustainability—A Critical Review

Jarosite precipitation remains an important route for removing ferric iron and incorporating sulfate into the precipitate in acidic hydrometallurgical liquors, yet process performance is often judged solely by iron removal. This structured critical narrative review evaluates jarosite as a coupled reaction–particle engineering–separation–residue system. The updated bibliography contains 102 references: 99 scientific sources used in the synthesis, two methodological sources, and one earlier authorial review retained only for transparent positioning of novelty. A documented literature update through 8 August 2026 adds recent evidence on integrated Fe–Pb–Zn recovery, selective Pb extraction, and indium recovery from industrial jarosite. Quantitative synthesis shows that operating windows and kinetic parameters are strongly system-dependent: reported examples range from industrial jarosite precipitation near 90–95 °C to low-temperature continuous precipitation, while apparent activation energies around 42–44 kJ mol−1 recur in selected crystallization/dissolution studies but do not establish a universal mechanism. Selectivity must be evaluated jointly with residual Fe, valuable-metal loss, particle size, filtration behavior, cake moisture, and residue stability. The revised six-gate framework therefore requires measurable evidence at each decision stage rather than a single Fe-removal target. The review identifies persistent gaps in high-ionic-strength thermodynamic modeling, standardized kinetic reporting, quantitative solid–liquid separation data, continuous pilot validation, closed mass balances, and integrated techno-economic/life-cycle assessment.