Cerium element Critical Material
Cerium (Ce), a lanthanoid chemical element. The United States' named cerium commodity designation is mapped to this element without extending it to every cerium compound. The experiment uses soluble CeCl3 and yields cerium-bearing phosphate/oxalate solids, not elemental cerium metal.
Identifiers & Classification
| System | Identifier | Label |
|---|---|---|
| CHEBI |
CHEBI:33369
|
cerium atom |
Criticality Designations
| Jurisdiction | List Name | Edition / Document | Classification | Source |
|---|---|---|---|---|
| United States | Department of the Interior Final List of Critical Minerals | 2025 final, published 7 November 2025 | critical |
us_2025
|
Microbial & Biochemical Mechanisms (1)
Cerium precipitation using pretreated biomass-free fungal struvite leachate
biomineralization
Microbial
Associated Organisms:
Aspergillus niger ATCC 1015 (NCBITaxon:380704)
Pretreated culture filtrate from Aspergillus niger ATCC 1015 growth on struvite-bearing material precipitated cerium-bearing phosphate and, at higher Ce loading, oxalate phases. Microbial involvement denotes upstream leachate production; the cerium reaction itself was cell-free.
Experimental Context & Analytical Limits:
Laboratory leachate came from 14-day fungal growth at 25 degrees C and 125 rpm in darkness, with 1% w/v pulverized natural struvite/dittmarite feed oven-treated at 105 degrees C for 48 h. Modified Czapek-Dox medium contained 1 g/L Na2HPO4 as background phosphate, with a 1 x 10^6 spores/mL inoculum. Biomass was removed by filtration. Leachate was treated with 0.5 g H-form AG 50W-X8 cation-exchange resin per 5 mL for 24 h, adjusted to pH 7.5 using 4 M NaOH, and filtered at 0.25 micrometers. CeCl3 at final 5, 20, 40 or 50 mM Ce3+ was mixed with treated leachate in 10 mL reactions for 24 h on a roller at room temperature, in triplicate. Solids were centrifuged, washed three times and dried. This is a laboratory precipitation experiment with synthetic cerium solution, not live-cell cerium reduction, isolated elemental-metal yield or industrial deployment.
Laboratory leachate came from 14-day fungal growth at 25 degrees C and 125 rpm in darkness, with 1% w/v pulverized natural struvite/dittmarite feed oven-treated at 105 degrees C for 48 h. Modified Czapek-Dox medium contained 1 g/L Na2HPO4 as background phosphate, with a 1 x 10^6 spores/mL inoculum. Biomass was removed by filtration. Leachate was treated with 0.5 g H-form AG 50W-X8 cation-exchange resin per 5 mL for 24 h, adjusted to pH 7.5 using 4 M NaOH, and filtered at 0.25 micrometers. CeCl3 at final 5, 20, 40 or 50 mM Ce3+ was mixed with treated leachate in 10 mL reactions for 24 h on a roller at room temperature, in triplicate. Solids were centrifuged, washed three times and dried. This is a laboratory precipitation experiment with synthetic cerium solution, not live-cell cerium reduction, isolated elemental-metal yield or industrial deployment.
Curated Evidence Points:
Support
Source:
kang_2022
Results and Figure 3 report greater than 99% removal of Ce from solution at the tested loadings. At 50 mM input, residual Ce was 27.34 +/- 1.91 micromolar; caption errors are SEM for at least three replicates. Supernatant Ce was measured by Arsenazo III colorimetry at 658 nm. Reported apparent complete removal at lower loadings does not establish literal zero residual concentration; the inspected method does not give a detection limit. Solution removal and weighed precipitate mass are not a pure-cerium yield.
Support
Source:
kang_2022
Figure 6 XRD with Table 2 Rietveld fits assigns CePO4.H2O at 20 mM CeCl3 and phosphate plus Ce2(C2O4)3.10H2O at 50 mM. Figure 9 FTIR supports phosphate and higher-loading oxalate assignments. Fitted phase proportions are not recovery percentages or proof of absolute phase purity. Subsequent high-temperature calcination results are separate from the microbial-associated step.
Partial
Source:
kang_2022
Resin treatment and alkaline adjustment are material process steps. The inspected full text does not report a matched synthetic phosphate/oxalate mixture or untreated-filtrate control for the cerium stage. Background medium phosphate prevents assigning all precipitate phosphorus to struvite. The study supports this prepared leachate's precipitation performance, not microbial necessity for precipitation, REE selectivity or performance on real cerium wastes.
Sources & References
-
chebi_cerium: ChEBI:33369 - cerium atom; formula Ce, net charge zero
https://www.ebi.ac.uk/chebi/CHEBI:33369 (accessed 2026-10-11) -
us_2025: U.S. Department of the Interior, U.S. Geological Survey. Final 2025 List of Critical Minerals, 7 November 2025, 90 FR 50494-50497, document 2025-19813; final table, Cerium row.
https://www.govinfo.gov/content/pkg/FR-2025-11-07/html/2025-19813.htm (accessed 2026-10-11) -
kang_2022: Kang, Csetenyi, Gao and Gadd (2022). Solubilization of struvite and biorecovery of cerium by Aspergillus niger. Applied Microbiology and Biotechnology 106:821-833. DOI 10.1007/s00253-021-11721-0; PMC8763747; Methods, Figures 3, 6 and 9, Table 2 and Discussion.
https://doi.org/10.1007/s00253-021-11721-0 (accessed 2026-10-11) -
ncbi_atcc1015: NCBI Taxonomy 380704 - Aspergillus niger ATCC 1015, no-rank strain entry
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=380704&mode=Info (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T04:55:52Z |
Codex (GPT-6; Codex) | CREATE | Created verified element identity and dated criticality with bounded Kang 2022 laboratory evidence, preserving feed, control and assay limits. |
Record source: data/records/cerium.yaml