CMMMech
CMMMech > Element > Europium

Europium element Critical Material

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.

Identifiers & Classification

System Identifier Label
CHEBI CHEBI:32999 europium 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)

Europium sorption associated with Anabaena sp. SAG 12.82 cultures

biosorption Microbial

Associated Organisms: Anabaena sp. SAG 12.82 (NCBITaxon:1840102)

Cultures exposed to europium nitrate showed reduced Eu in separated supernatants and qualitative Eu signals in harvested biomass. Electron-dense intracellular deposits were reported after Eu exposure, but their composition and oxidation state were not established by particle-specific analysis. Neither a demonstrated Eu(III)-to-Eu(0) reduction nor an exclusively metabolic uptake route is asserted.

Experimental Context & Analytical Limits:
Fischer et al. used SAG 12.82 cultures grown in 150 mL modified Bold's Basal Medium in 250 mL flasks, with nitrate reduced to 50%, initial medium pH 6.8, reported culture pH 7.3, 22 degrees C, orbital shaking and a 12 h day/night cycle (4200 K light). Cultures were divided into salt-exposed and untreated references. Separate assays used 0.111 mM initial Eu in nutrient medium and 0.191 mM in a nutrient-starved culture. Initial biomass concentration, biological replicate count and a matched biomass-free time course are not specified in the inspected main article or supplement. The initial concentration reference was appropriately diluted stock without biomass, not an incubated abiotic control. Samples of 2 mL were centrifuged at 14000 rpm for 15 min; supernatants were filtered through 0.45 micrometre filters, acidified, frozen and measured by ICP-MS. Sampling had stated temporal uncertainty of +/- 10 min. ICP-MS measures elemental Eu rather than proving dissolved Eu(III) speciation. Washed, dried biomass was examined by qualitative LIBS; these spectra cannot quantify biomass loading. Cultures appeared viable by color and optical microscopy, without a quantitative viability or killed-cell comparison. The current SAG catalogue lists this strain as non-axenic; the experimental article does not verify culture purity, so associated microbes cannot be excluded. Dose and nutritional state change together between the Eu arms. No recovery from real waste, desorption yield or isolated Eu product was demonstrated.
Curated Evidence Points:
Table S1 and Figure S1 (page S2) give 0.111 mmol/L initially, 2.47E-3 mmol/L at 57 min and 6.16E-4 mmol/L at 1692 min in the fed arm. These are about 97.8% and 99.4% decreases, respectively, calculated from the reported initial reference; they are not recovered-product yields. Table S4 and Figure S4 (page S5) give 0.191 mmol/L initially, 5.79E-2 at 40 min, 2.21E-2 at 65 min, 2.85E-2 at 185 min and 4.03E-2 mmol/L at 1490 min in the starved arm. The later increase is retained. The supplement labels an error column RSD in mmol/L without explaining its statistical basis or replicate count; no confidence interval is inferred.
Experimental and Results, ICP-MS and LIBS, with Figures 1-3, support culture-associated solution depletion and qualitative biomass enrichment. Main-text summaries conflict with the supplement: a discussion claim of 99.4% removal after one hour does not match the 57 min Table S1 value, and near-total starved uptake at three hours does not match Table S4. The paper's visual absence of precipitation is not a matched abiotic precipitation control. These data do not isolate the fraction caused by living cyanobacteria, passive binding, extracellular precipitation or associated organisms, and the fed/starved comparison does not establish metabolic causality.
Results, TEM and XRD, Figure 8 captions, Discussion and Conclusion report electron-dense deposits in heterocysts at 10 and 28 h, unlike the abstract's vegetative-cell wording. This localization conflict is explicit; the Results account is retained as an attributed observation, not independently remeasured microscopy. The authors report no Bragg reflections at 6, 28 or 200 h and acknowledge missing oxidation-state measurements. Neither electron density nor a negative bulk XRD result identifies a pure Eu phase or rules out all noncrystalline Eu compounds. The proposed biomolecule-complexed Eu species remain a hypothesis.
Context_only Source: sag_1282
The live strain catalogue confirms Anabaena spec. SAG 12.82 and currently lists bacterial and other contamination. This supports the culture-purity caveat, without proving which associates were present in the 2019 experiment or their contributions.
The later primary article's Sections 2-4 describe further image analysis of Eu-exposed SAG 12.82 heterocysts and call the Eu deposits amorphous. Its abstract also uses bioreduction language, but the inspected methods provide no new Eu oxidation-state assay. The record therefore does not upgrade the 2019 observation to Eu(0), enzyme causality or recovered product. Detailed particle-size distributions from this later study are outside this curated assay.

Sources & References

  1. chebi_europium: ChEBI CHEBI:32999 - europium atom; formula Eu, net charge 0
    https://www.ebi.ac.uk/chebi/CHEBI:32999 (accessed 2026-10-11)
  2. usgs2025: USGS (2025). Final 2025 List of Critical Minerals. Federal Register 90:50494-50497, document 2025-19813; europium row on page 50496.
    https://www.govinfo.gov/content/pkg/FR-2025-11-07/html/2025-19813.htm (accessed 2026-10-11)
  3. fischer2019: Fischer et al. (2019). Cyanobacterial promoted enrichment of rare earth elements europium, samarium and neodymium and intracellular europium particle formation. RSC Advances 9:32581-32593; Experimental, Results, Discussion and Figures 1-9.
    https://doi.org/10.1039/C9RA06570A (accessed 2026-10-11)
  4. fischer2019_esi: Fischer et al. (2019), electronic supplementary information, RA-009-C9RA06570A-s001.pdf; pages S1-S5, Tables S1-S4 and Figures S1-S4. Complete PDF entry recovered with matching CRC32 from the incomplete EuropePMC ZIP download.
    https://www.ebi.ac.uk/europepmc/webservices/rest/PMC9073238/supplementaryFiles (accessed 2026-10-11)
  5. sag_1282: SAG culture catalogue, strain 12.82, Anabaena spec.; presently non-axenic, with bacterial and other contamination
    https://sagdb.uni-goettingen.de/detailedList.php?str_number=12.82 (accessed 2026-10-11)
  6. ncbi_sag1282: NCBI Taxonomy 1840102 - Anabaena sp. SAG 12.82; strain-named species-rank node
    https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=taxonomy&id=1840102&retmode=xml (accessed 2026-10-11)
  7. fritz2023: Fritz et al. (2023; published online 2022). Time-Dependent Size and Shape Evolution of Gold and Europium Nanoparticles from a Bioproducing Microorganism, a Cyanobacterium: A Digitally Supported High-Resolution Image Analysis. Nanomaterials 13:130; Sections 2-4, reviewed for limits of oxidation-state claims.
    https://doi.org/10.3390/nano13010130 (accessed 2026-10-11)

Curation History

Timestamp Curator Action Summary
2026-10-11T06:02:59Z Codex (GPT-6; Codex) CREATE Added verified elemental europium identity, dated US2025 designation and qualified cyanobacterial sorption evidence; preserved primary-source inconsistencies, analytical limits and laboratory scope. Scientific review is separate.

Record source: data/records/europium.yaml