Biosorption Mechanisms

Birnessite is a layered manganese oxide mineral, listed as grandfathered in the September 2026 IMA-CNMNC list with formula (Na,Ca,K)0.6(Mn4+,Mn3+)2O4(H2O)1.5. Its composition and polytype vary. It is distinct from elemental manganese, mixed manganese ore and nodules, the buserite precursor used to prepare some synthetic analogues, and manganese oxalate products. The mechanisms below concern separately prepared synthetic sodium and cobalt-bearing forms, and a source-assigned poorly crystalline biogenic Mn-oxide/fungal composite. They do not establish behavior for natural ore or every birnessite polytype. No criticality designation is inherited from manganese.

• Aspergillus niger
• Serpula himantioides
• Paraconiothyrium sp. WL-2

The element Dy, distinct from its dissolved ions, salts, magnets, minerals and waste streams. The dated US designation concerns the named dysprosium mineral commodity, without assigning criticality to every Dy-bearing material. The mechanism records a laboratory study of dried brewing-yeast biomass with synthetic Dy solutions; it does not establish recovery from actual industrial effluent or a purified dysprosium product.

• Saccharomyces cerevisiae

Metal-bearing liquids originating from industrial electroplating baths, represented by five Cu, Ni, Pd and Au bath effluents supplied by Galvanica Aricci Srl, Ghisalba, Italy, in Ciani et al. (2026). These compositionally different process liquids are distinct from electroplating wastewater-treatment sludge, metallic electroforming scrap and laboratory metal-salt solutions. The study's Ni(1)+Cu mixture is an experimental combination of two supplied liquids, not a sixth independently sampled waste stream. No criticality designation is inherited from constituent metals.

• Dactylococcopsis salina 16Som2
• Cyanothece sp. CE4

The element Eu, distinct from Eu(III), europium nitrate, oxides, mineral species and waste streams. The dated US designation concerns the named europium mineral commodity and does not transfer criticality to every Eu-bearing material. Laboratory evidence below concerns cyanobacterial culture-associated removal from synthetic solutions; it does not establish selective extraction, a purified product or industrial deployment.

• Anabaena sp. SAG 12.82

The element In, distinct from indium ions, salts, indium tin oxide and indium-bearing minerals or waste streams. The dated US designation concerns the named indium mineral commodity. The mechanism describes laboratory biosorption from synthetic solutions by prepared mixed microalgal biomass; it does not establish treatment of an actual indium waste stream or recovery of an isolated indium product.

Iridium (Ir), distinct from experimental hexachloroiridate(IV), metallic alloys and iridium-bearing ores or waste streams. The US 2025 list names iridium individually; this designation is mapped to the element without extending it to every Ir-bearing material. Curated evidence concerns laboratory adsorption and desorption using lyophilized unicellular algal biomass in synthetic solutions, not reduction to Ir metal or deployment.

• Galdieria javensis

Lutetium is the element Lu, represented here by its neutral-atom identity, distinct from dissolved Lu(III), chloride feed, host minerals and mixed rare-earth commodities. The United States designation refers to the named element in the Final 2025 List of Critical Minerals. A laboratory mixed-chloride experiment supports lutetium biosorption associated with washed Bacillus subtilis biomass; it does not establish a purified lutetium product or industrial recovery.

• Bacillus subtilis

The element Nd. The identifier grounds the element, not an Nd(III) ion, mineral species, magnet alloy, or discarded magnet. The US designation below concerns the named neodymium mineral commodity in the separate 2022 and 2025 lists; these dated designations do not assign criticality to every Nd-bearing resource. The mechanisms distinguish biosorption from microbial production of a lixiviant that releases Nd from a synthetic phosphate substrate.

• Chlorella vulgaris
• Gluconobacter oxydans

Rhenium (Re), represented as an element distinct from its ions, compounds, isotopes, host minerals, alloys and commodity streams. The US 2025 designation names the rhenium commodity and does not designate every compound or host material. A laboratory batch study tested inactive brewer's yeast biomass for rhenium association from synthetic perrhenate solutions. This biosorption record does not assert microbial rhenium reduction or isolated-metal recovery.

• Saccharomyces cerevisiae

The element Sm, distinct from Sm(III), samarium nitrate, mineral species, alloys and waste streams. The dated US designation concerns the named samarium mineral commodity, without assigning that designation to every Sm-bearing material. The mechanism concerns laboratory culture-associated depletion from a synthetic solution and qualitative biomass enrichment, not a purified samarium product or industrial process.

• Anabaena cylindrica PCC 7122

Naturally occurring marine saline water considered as a dissolved-material extraction feed. It is a variable aqueous resource, distinct from elemental uranium, a mineral species, a manufactured salt product and desalination concentrate. The curated study used natural seawater in a laboratory dialysis experiment with nutrient-supported bacterial growth. Its composition and response do not define all seawater. No criticality designation or external material identifier is inferred from its constituents.

• Bacillus velezensis

Discarded neodymium-iron-boron permanent-magnet material considered as a secondary resource, distinct from the neodymium element, a fixed-purity Nd2Fe14B compound, all rare-earth magnets, and the broader commodity grouping of raw materials for permanent magnets. Actual feeds can contain other rare earths, alloying elements, coatings and impurities; no universal composition is assigned. Riano and Binnemans document an end-of-life NdFeB feed. The microbial-origin biomass assay curated here instead used chemically prepared hard-disk-magnet leachate; its precise device history and waste collection provenance were not reported. This is the same Kucuker experiment represented under neodymium, not an independent replication or a criticality designation inherited from its constituent elements.

• Chlorella vulgaris

Aqueous waste streams from tanning operations, represented here by conventionally treated effluent from the Acque del Chiampo plant in Arzignano, Italy. This heterogeneous secondary resource is distinct from wastewater-treatment sludge, chromium-tanned leather shavings, synthetic chromium solutions and elemental chromium. The accepted laboratory study concerns further removal of residual source-assigned Cr(III) using dead fungal biomass; composition and performance are specific to the tested feeds. No constituent criticality is inherited.

• Cunninghamella elegans

The element Tb, distinct from its dissolved ions, salts, host minerals, phosphors and waste streams. The dated US designation concerns the named terbium mineral commodity; it does not assign criticality to every Tb-bearing material. The curated mechanism is a laboratory screening observation using lyophilized cyanobacterial biomass and a synthetic terbium solution, without demonstrated isolated-product recovery.

• Synechococcus elongatus UTEX 2973

Thulium is the element Tm, represented by its neutral-atom identity and distinct from Tm(III) chloride solutions, mineral hosts and rare-earth commodities. It is named in the United States Final 2025 List of Critical Minerals. Prepared Bacillus subtilis cell powders provide laboratory evidence for thulium biosorption and subsequent acidic elution, without an isolated pure-metal yield or demonstrated industrial process.

• Bacillus subtilis subsp. subtilis str. 168

Heterogeneous solid residue described by the source as titanium gypsum or titanogypsum from titanium-dioxide production. The curated feed is a real Taizhou, Jiangsu plant waste, distinct from natural gypsum, titanium dioxide, phosphogypsum from phosphoric-acid manufacture and a purified calcium-sulfate product. Its unusual reported bulk composition and mixed phase assignments are retained rather than imposing pure-gypsum stoichiometry. Laboratory culture-associated redistribution of fluorine does not establish recovery of a fluorine product, a safe agricultural amendment or industrial deployment. No constituent-element criticality is inherited.

• Rhodotorula mucilaginosa