Integrated Process Routes for Spent Pot Lining Valorization: From Hazard Detoxification to Closed-Loop Recovery of Fluorides, Carbon, and Refractories

Spent pot lining (SPL) is simultaneously a hazardous residue and a heterogeneous secondary resource containing carbon, fluoride-bearing electrolyte, sodium, aluminum, refractory minerals, and reactive or cyanide-bearing species. This structured critical narrative review reframes SPL management as a flowsheet-integration problem rather than a competition among isolated physical, hydrometallurgical, thermal, or co-processing technologies. A fixed core evidence corpus of 106 publications from January 2020 through 19 August 2026, supplemented only by three pre-2020 foundational or regulatory sources excluded from corpus counts, is assessed according to feed fraction, hazard destruction, elemental recovery, reagent and water demand, energy intensity, product quality, secondary residues, evidence scale, and industrial integration. Eight integrated process architectures are compared, ranging from physical separation plus selective hydrometallurgy to thermal-hydrometallurgical hybrids, direct co-processing, closed-loop aluminum-smelter recycling, and a near-zero-waste SPL-refinery concept. The central finding is that high extraction alone is an insufficient measure of circularity: carbon, fluorine, sodium, aluminum, and cyanide-bearing species must be tracked to qualified products, recycle streams, controlled emissions, or final residues. Carbon-rich first-cut SPL generally favors selective defluorination followed by carbon upgrading, whereas refractory-rich second cut requires mineral-oriented recovery or controlled co-processing. Thermal steps are most defensible when they solve a defined hazard or separation constraint and when condensates and off-gases are deliberately recovered. Hydrometallurgical routes offer stronger control over fluoride recovery but can shift burdens to reagent consumption, saline liquors, and water treatment. The most promising long-term architecture is feed-adapted and hybrid, but the evidence base remains laboratory-dominant. Research priorities are representative pilot campaigns, full constituent balances, product qualification, recycle-loop stability, and coupled techno-economic and life-cycle assessment.