Recovery Mechanisms

Alunite is the potassium aluminium hydroxysulfate mineral KAl3(SO4)2(OH)6, listed by IMA-CNMNC in September 2026 as redefined, 1987 s.p. It is a distinct species within the alunite group, not a label for every aluminium sulfate or mixed mining residue. Zhong et al. (2019) examined a natural alunite-bearing ore containing quartz and kaolinite. Their laboratory CaO-assisted thermal treatment followed by water leaching increased soluble potassium under selected conditions; the separate evaporation product remained a mixture of potassium/calcium sulfate phases. The accepted experiment is abiotic and does not establish microbial extraction, a pure potassium product, complete aluminium recovery, or industrial deployment. No constituent-element criticality is inherited.

Discarded lead-bearing cathode-ray-tube (CRT) glass is a composite secondary resource for lead recovery, distinct from elemental lead, a lead mineral, separated CRT fluorescent powder and spent fluorescent-lamp phosphor. The accepted laboratory feed is described as waste CRT glass and contains 22.08 wt.% PbO in the source composition table. Its exact component, supplier and device history are not reported. The source's general distinction between lead-bearing funnel/neck glass and typically non-leaded screen glass does not establish that this experimental sample was a separately collected funnel fraction. Constituent criticality designations are not inherited.

Discarded hardmetal production components composed of tungsten carbide with cobalt or cobalt-nickel binder, represented by rolling-mill rollers and brazed cutting tips in the Chaika study. This manufactured secondary resource is distinct from pure tungsten carbide, a mineral species, tungsten mining tailings and metal grinding sludge. The sampled shapes and compositions do not define every hardmetal waste stream. No criticality designation or industrial deployment is inferred.

• Acidithiobacillus ferrooxidans

Heterogeneous solid residue generated by coal gasification, including source-defined crude/coarse and fine fractions. This processing-derived resource is distinct from coal, coal-beneficiation waste and combustion-derived coal fly ash; it is neither a mineral species nor an aluminium or iron commodity. The accepted experiment concerns one supplied coal gasification crude slag (CGCS) sample and does not establish the same behavior for fine slag or other plants. Laboratory abiotic acid leaching and conversion of the liquors into a mixed flocculant are documented; constituent-element criticality is not inherited.

Zinc-bearing dust generated by electric-arc-furnace steelmaking, represented here by two actual dusts supplied by an unnamed steelmaking company. This process-defined secondary resource is distinct from cast-house dust, blast-furnace flue-gas dust, steelmaking slag, zinc ore and elemental zinc. The two samples do not define a universal composition. No elemental identifier or criticality designation is assigned to the dust.

• Acidithiobacillus thiooxidans

Defective electroformed copper components retaining an inner silver-bearing conductive coating from manufacture on expendable wax mandrels. The studied tube-shaped rejects had incomplete copper deposition or uneven wall thickness. This manufacturing-derived secondary resource is distinct from elemental copper or silver, printed circuit boards, electroplating sludge and multilayer beverage packaging. Its selected composition does not define all electroforming waste or confer a jurisdictional criticality designation.

• Acidithiobacillus ferruginosus

Discarded crystalline-silicon photovoltaic modules and their separated cell fractions are a composite secondary resource generated by photovoltaic equipment use and dismantling. Their silicon wafers, metal contacts, glass and encapsulants remain distinct from elemental silicon, silicon-metal commodity, silver and mineral species. This record excludes CdTe and CIGS thin-film modules, manufacturing scrap of unspecified origin and generic electronic waste. The curated experiment used a chemical extract from end-of-life Hyundai m-Si units, not intact modules in direct contact with microorganisms. Criticality designations of constituent elements are not inherited by this waste feed.

A beneficiated geological feed represented by the TANBREEZ concentrate from southern Greenland characterized by Ma and colleagues (2019). The source describes crushing followed by partly magnetic selection; this is an upgraded mixed mineral concentrate, distinct from the uncharacterized crushed eudialyte ore in Hunter's 2020 thesis, a formal eudialyte mineral species or group, elemental zirconium and recovered rare-earth products. Table I reports 1.60 wt% total rare earth elements and 6.46 wt% Zr in the laboratory feed. QEMSCAN assigns 67.05% of the material to eudialyte, alongside amphibole, nepheline, feldspar and other phases; this classification does not establish a pure species or a universal commercial concentrate specification. The source acknowledges the Geological Survey of Finland as concentrate supplier. No criticality designation is inherited from constituent elements.

Source-labelled samarium-cobalt magnet scrap supplied by the Defence Metallurgical Research Laboratory, Hyderabad, India. Its preceding service history and manufacturing-waste category were not disclosed, so the feed is not asserted to be end-of-life devices. It is distinct from NdFeB magnet waste, the broad rare-earth permanent-magnet commodity grouping, pure Sm2Co17 and its constituent elements. The characterized preparation includes oxide phases as well as a Sm2Co17 assignment. No criticality designation or microbial recovery is inherited from the feed's constituents.

End-of-life non-button alkaline and zinc-carbon batteries, represented by a mixed AA-cell powder after dismantling, electrolyte washing and drying. This secondary resource is distinct from the curated watch/button-cell powder, nickel-metal-hydride batteries and lithium-ion battery black mass. The selected experiment treats the two primary-cell chemistries together; it does not establish separate chemistry-specific performance or a universal battery composition. Constituent-element criticality is not inherited.

• Acidithiobacillus thiooxidans

Used aqueous glass-polishing suspension containing ceria-based abrasive, fine glass particles and other process-derived components. The curated 2015 case is waste collected in several portions over six months from the Dioptra optical-glass-polishing factory in Turnov, Czech Republic, which used Cerox-type ceria polishing powders. Sedimentation partially dewatered the waste to approximately 50% water before treatment. Table 1 reports dry-solid XRF composition as oxide equivalents, including 8.85 wt% CeO2, 1.49 wt% La2O3 and 57.6 wt% SiO2. These are a reported waste-composition example, not universal proportions or quantitative mineral abundances. The mixed used slurry is distinct from pure cerium, reagent ceria, fresh polishing powder and the recovered ceria-rich product. Constituent criticality is not inherited by this resource.

Used CuO-ZnO-Al2O3 catalyst material from synthesis-gas processing, including low-temperature carbon monoxide conversion. This composition-defined secondary resource is distinct from fresh catalyst, its constituent oxides, elemental copper/zinc and spent refinery hydroprocessing catalysts. The selected Polish-market sample had 35.1 wt% Cu, 29.9 wt% Zn and 9.2 wt% Al by AAS; these are sample measurements, not a universal formulation. Its plant and service history are unspecified. No constituent criticality is inherited.

Used iron-molybdate catalyst from methanol oxidation for formaldehyde production. This process-defined secondary resource contains iron molybdate and excess molybdenum oxide, with feed-specific impurities and amorphous material. It is distinct from molybdenite, elemental molybdenum, fresh catalyst and spent Ni/Co-Mo refinery catalysts. Two primary studies examine different spent feeds; their compositions and yields are not interchangeable. No mineral identifier or constituent-element criticality is assigned.

Spent indium-tin oxide targets are a solid secondary resource associated with sputtering-target use, distinct from elemental indium or tin, virgin ITO products, LCD glass panels and dissolved etching wastewater. Gu and colleagues identify their supplied Wako material as spent ITO target material and analyze its ground powder. The specific prior sputtering history and service conditions are not documented in the accessible main article, so the spent designation is retained as the study's feed description. Its mixed oxide composition and impurities are sample-specific, not a universal target specification. No criticality designation is inherited from constituent elements.

Exhausted aluminium-smelting cell lining containing variable proportions of carbonaceous cathode material, refractory cement and brick, and accumulated process salts. The accepted study used real mixed-cut waste supplied by Trimet Aluminium, Essen, Germany, with three visually selected grades from refractory-rich to mainly graphitic material. Exact cell and service histories were not resolved. This solid waste is distinct from aluminium dross, waste electrolyte, red mud, graphite as a mineral or commodity, and its constituent elements. Laboratory chemical extraction is documented without a microbial mechanism or an inherited criticality designation.

Sulfuric-acid electrolyte containing dissolved vanadium in multiple oxidation states after use in all-vanadium redox flow batteries. This use-derived liquid resource is distinct from elemental vanadium, fresh electrolyte products, spent vanadium catalysts, and solid battery scrap. The two studies below concern different feeds: company-supplied failed positive/negative electrolytes and electrolyte deliberately cycled to capacity loss in a laboratory cell. Their outcomes are not interchangeable. No constituent criticality designation or microbial mechanism is inherited.

Discarded tungsten-nickel-iron heavy-alloy components, represented by decommissioned projectile cores identified as VNZh in the Baranov study. This manufactured secondary resource is distinct from elemental tungsten, cemented tungsten carbide scrap, mining tailings and grinding-fluid sludge. The reported feed composition describes the tested material, not every VNZh grade or tungsten-alloy waste. No criticality designation, standardized product specification or industrial deployment is inferred.

Silver-bearing liquid discarded after photographic fixing, represented here by used black-and-white film fixer collected from a local processing unit. This secondary feed is distinct from discarded solid films, unused fixer, developer solutions and prepared silver salts. Its composition is source-specific; constituent criticality is not inherited.

• Thiobacillus thioparus
• Cladosporium cladosporioides

Used silver-bearing radiographic films obtained from medical facilities, comprising a gelatin-silver emulsion on a polymer base. The curated feeds are discarded X-ray films, not unused film stock, photographic processing liquids, elemental silver or all photographic wastes. Laboratory studies distinguish microbial-enzyme stripping of the emulsion from subsequent thermal production of silver metal. No constituent criticality designation or industrial deployment is inherited.

• Conidiobolus coronatus
• Bacillus spizizenii ATCC 6633 = JCM 2499