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Scandium element Critical Material

The element Sc, distinct from dissolved Sc(III), scandium chloride, scandium oxide, Sc-bearing minerals and waste feedstocks. The US2025 designation concerns the named scandium mineral commodity. Laboratory evidence below uses an immobilized bacterial protein and synthetic dissolved-metal mixtures; it does not demonstrate living-cell extraction.

Identifiers & Classification

System Identifier Label
CHEBI CHEBI:33330 scandium atom

Criticality Designations

Jurisdiction List Name Edition / Document Classification Source
United States of America USGS Final List of Critical Minerals 2025; Federal Register 90:50494-50497, 7 November 2025 critical usgs2025

Microbial & Biochemical Mechanisms (1)

Cell-free lanmodulin capture and malonate elution of scandium

separation Microbial

Associated Organisms: Methylorubrum extorquens (NCBITaxon:408)

Purified M. extorquens lanmodulin with a C-terminal GSGC addition, covalently attached to maleimide-functionalized agarose, retained Sc(III) from a synthetic rare-earth mixture. Malonate subsequently released Sc selectively. Microbial involvement denotes the bacterial origin and recombinant production of the protein; the separation itself was cell-free and chemically driven, without growth or metabolism.

Experimental Context & Analytical Limits:
The cited preparation method expressed LanM-GSGC in Escherichia coli BL21(DE3), followed by protein purification and thiol-maleimide coupling; the expression host is distinct from the protein-origin species. Figure 5 used chloride-salt mixtures at pH 3, a 5 cm by 0.5 cm column, 0.9 mL bed volume, loading to a reported 70% capacity, a five-bed-volume water wash and the default 0.5 mL/min flow. The malonate scheme used 30 then 50 mM at pH 5. Mixed-metal effluents were analyzed by ICP-MS. Column breakthrough tests used one run; triplicate feed analyses quantify analytical variation rather than independent process replication. Column temperature was not specified in the inspected methods. This was a synthetic solution resembling selected leachate compositions, not a real ore, waste treatment run or industrial operation.
Curated Evidence Points:
Section 3.4 and Figure 5E-F report Sc elution above 99 mol% purity among REEs and above 99% yield for the two-step malonate process. The Methods define yield as recovered target REE divided by total target REE loaded. This is an aqueous Sc fraction, not isolated metal or oxide. Figure 3C independently shows selective Sc release from an approximately equimolar mixture at 30 mM malonate. Figure 4 uses soluble-protein fluorescence and circular dichroism as supporting binding assays; the reported picomolar affinity is a fitted, model-dependent apparent constant, not a recovery yield.
The citrate comparator in Section 3.4 gave about 96 mol% Sc purity at 78% yield and required stronger citrate for tailing Sc. Performance therefore depends on the desorption chemistry. Figure 5 names a nominal 0.4 mM total-REE feed and refers to Table S9, but the appended supplement labels that feed Table S10; its 16 mean concentrations sum to 0.2430 mM, including Sc at 23.8 +/- 1.1 micromolar. These source inconsistencies are unresolved and no reconciled feed concentration or independently recomputed mass balance is asserted. A matched Sc-only resin-without-LanM column was not reported in the inspected study, limiting attribution of every contribution to binding. No general Sc separation efficiency across feedstocks is established.
Context_only Source: dong2021
Supplement pages S2-S4 establish the recombinant expression, purification and immobilization protocol expressly referenced by Dong2024. Its maleimide-resin comparator and Nd experiments are methodological context, not a direct Sc control or Sc yield.

Sources & References

  1. chebi_scandium: ChEBI CHEBI:33330 - scandium atom; formula Sc, net charge 0
    https://www.ebi.ac.uk/chebi/CHEBI:33330 (accessed 2026-10-11)
  2. usgs2025: USGS (2025). Final 2025 List of Critical Minerals. Federal Register 90:50494-50497, document 2025-19813; named scandium entry.
    https://www.govinfo.gov/content/pkg/FR-2025-11-07/html/2025-19813.htm (accessed 2026-10-11)
  3. dong2024: Dong, Mattocks, Seidel, Cotruvo and Park (2024; online 2023). Protein-based approach for high-purity Sc, Y, and grouped lanthanide separation. Separation and Purification Technology 333:125919. OSTI2315086 accepted manuscript and appended supplement; Methods, Figures 3-5, Section 3.4 and supplement Table S10.
    https://doi.org/10.1016/j.seppur.2023.125919 (accessed 2026-10-11)
  4. dong2021: Dong et al. (2021). Bridging Hydrometallurgy and Biochemistry: A Protein-Based Process for Recovery and Separation of Rare Earth Elements. ACS Central Science 7:1798-1808; Supporting Information pages S2-S4 for recombinant protein preparation and immobilization.
    https://doi.org/10.1021/acscentsci.1c00724 (accessed 2026-10-11)
  5. ncbi_extorquens: NCBI Taxonomy 408 - Methylorubrum extorquens; species-level protein-origin context
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=408 (accessed 2026-10-11)

Curation History

Timestamp Curator Action Summary
2026-10-11T06:27:14Z Codex (GPT-6; Codex) CREATE Added verified elemental identity, dated US2025 criticality and qualified cell-free protein separation evidence after primary-source inspection; retained experimental and source limitations. Independent scientific review is recorded separately.

Record source: data/records/scandium.yaml