CMMMech
CMMMech > Element > Platinum

Platinum element Critical Material

Platinum (Pt). The element is distinct from its experimental dissolved chloro-complexes, the potassium salts used to prepare them, and platinum-bearing minerals or wastes. The US 2025 designation names the platinum commodity individually; it is mapped here to the element without designating every platinum compound or secondary resource as critical. Curated evidence concerns laboratory transformation in the presence of bacterial biomass, with substantial abiotic reduction and no demonstrated isolated-metal yield or industrial use.

Identifiers & Classification

System Identifier Label
CHEBI CHEBI:33364 platinum atom

Criticality Designations

Jurisdiction List Name Edition / Document Classification Source
United States of America U.S. Department of the Interior Final List of Critical Minerals 2025 (published November 7, 2025; 90 FR 50494-50497) critical usgs_2025

Microbial & Biochemical Mechanisms (1)

Hydrogen-driven Pt(II) transformation in the presence of CH34 biomass

redox transformation Microbial

Associated Organisms: Cupriavidus metallidurans CH34 (NCBITaxon:266264)

Washed Cupriavidus metallidurans CH34 biomass exposed to a synthetic Pt(II) chloro-complex under hydrogen acquired platinum-bearing particles. The authors interpreted biomass-associated XANES and EXAFS spectra as consistent with metallic Pt(0). Hydrogen alone also removed Pt(II), so the experiment supports a transformation with microbial biomass present, without establishing that living cells or a particular enzyme are necessary.

Experimental Context & Analytical Limits:
Laboratory anaerobic batches: CH34 from SCK-CEN was first grown aerobically overnight in LB-Lennox at 28 degrees C, centrifuged at 7000 g for 7 minutes, washed twice with 25 mL phosphate buffer (8.5 g/L Na2HPO4.7H2O and 3 g/L KH2PO4), and resuspended to OD610 of 1. Fifty mL suspensions in 120 mL serum bottles received Pt(II) supplied as K2PtCl4, at 100 mg/L Pt from a 2.5 g/L Pt stock in 1 M HCl. Bottles underwent 20 nitrogen/vacuum cycles and the headspace was replaced with 100% hydrogen; batches were mixed at 100 rpm and 28 degrees C, with initial assay pH adjusted to 1.8-2.2. Aerobic denotes biomass cultivation, not the anaerobic transformation assay. Table 1 reports 99% Pt removal with hydrogen at 48 h versus 24% in the no-electron-donor CH34 arm and 99% in the chemical hydrogen control (screening experiments n=1). These ICP-OES-based removal percentages are not measured Pt(0) fractions or purified-product yields; the 2017 methods refer detailed ICP sample preparation to an earlier paper, whose full procedure was not verified here. Membrane-intact cell counts decreased during exposure, so sustained metabolic activity is not assumed.
Curated Evidence Points:
Methods, Figure 1, supplementary Figure S1, and the Platinum speciation analysis section support the authors' Pt(0) interpretation for aerobically cultivated CH34 exposed to Pt(II) under hydrogen. Figure 3 shows particulate deposits in the CH34 Pt(II) panel. The phase claim depends on X-ray absorption evidence, not the color change or microscopy alone, and is not a quantitative determination of complete conversion.
Table 1's chemical hydrogen control also reaches 99% Pt(II) removal; thus the CH34 endpoint does not establish a microbial enhancement over that abiotic arm. The paper additionally reports 99% removal with heat-killed Shewanella cells, a different organism and not a matched CH34 viability control. No specific hydrogenase or other enzyme was demonstrated to cause Pt reduction in CH34.
Figure 5 and the membrane-integrity results show CH34 intact-cell counts declining to the assay detection level by 27 h in the acidic Pt(II)/hydrogen experiment. Membrane staining is not proof of growth or metabolic activity. Table 1 also reports only 3% carboplatin removal and zero for the tetraamine preparation with CH34 and hydrogen; the Pt(II) chloro-complex result cannot be extended to all Pt complexes.
Spectroscopy reporting has unresolved internal inconsistencies: Methods specifies the Pt L3 edge and a 11919 eV calibration value, while Figure 1 is plotted near 11560-11630 eV and Results calls the edge K-edge. This record retains the authors' qualitative XANES/EXAFS interpretation without adopting those conflicting absolute energy assignments or claiming independent spectral refitting. The source also distinguishes solution removal from reduced Pt in biomass.

Sources & References

  1. chebi_platinum: ChEBI:33364 - platinum atom; Pt, charge 0
    https://www.ebi.ac.uk/chebi/CHEBI:33364 (accessed 2026-10-11)
  2. usgs_2025: U.S. Geological Survey (2025). Final 2025 List of Critical Minerals. Federal Register 90 FR 50494-50497, November 7, 2025; final commodity table, Platinum row.
    https://www.govinfo.gov/content/pkg/FR-2025-11-07/html/2025-19813.htm (accessed 2026-10-11)
  3. maes_2017: Maes et al. (2017). Biological Recovery of Platinum Complexes from Diluted Aqueous Streams by Axenic Cultures. PLOS ONE 12(1), e0169093. DOI 10.1371/journal.pone.0169093. Methods, Table 1, Figures 1, 3 and 5, supplementary Figure S1 and Table S1.
    https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0169093 (accessed 2026-10-11)
  4. ncbi_ch34: NCBI Taxonomy: Cupriavidus metallidurans CH34, Taxonomy ID 266264
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=266264&mode=Info (accessed 2026-10-11)

Curation History

Timestamp Curator Action Summary
2026-10-11T04:36:09Z Codex (GPT-6; Codex) create Created the platinum element record after verifying identity, the US 2025 designation, and Maes et al. 2017 CH34/Pt(II)/hydrogen evidence. Preserved abiotic removal, biomass-state limitations, unreplicated screening, complex-specific nulls and source spectroscopy inconsistencies. Attached canonical CREATE history; independent scientific review is separate.

Record source: data/records/platinum.yaml