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Gallium element Critical Material

Gallium (Ga), grounded by the neutral-atom ChEBI identifier. This element record is distinct from gallium ions, gallium arsenide semiconductor material and the heterogeneous hydroxide sludge used in the experiment. The US 2025 designation maps its gallium commodity to this element; it does not designate every gallium-bearing waste. The arsenic record describes co-mobilization in the same experiment, not an independent replication.

Identifiers & Classification

System Identifier Label
CHEBI CHEBI:49631 gallium 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; published 7 November 2025 critical usgs2025

Microbial & Biochemical Mechanisms (1)

Gallium mobilization during sulfur-oxidizing sludge bioleaching

bioleaching Microbial

Associated Organisms: Acidithiobacillus thiooxidans (NCBITaxon:930)

Living Acidithiobacillus thiooxidans cultures supplied acidity during laboratory leaching of hydroxide sludge from GaAs wafer manufacture. Gallium entered the leachate largely because of acidic conditions; the culture-associated increment over acid-adjusted controls remains provisional. Ferric-iron reduction was observed, but a specific microbial gallium redox reaction or purified gallium product was not demonstrated.

Experimental Context & Analytical Limits:
The type strain DSM 14887 was adapted to 5% w/v sludge with aluminum; NCBITaxon:930 identifies the species, not the strain. The feed was dried at 60 degrees C for 48 hours and mortar-homogenized; Table 1 reports 1.21% Ga by handheld XRF and Section 2.1 expects association with the iron phase rather than establishing a gallium mineral species. The curated 3% w/v sludge assay used 50 mL shake-flask setups, HBS medium, 1% elemental sulfur, initial pH 1.8, 30 degrees C and eight days. Table 2 specifies 12.9 mM Al (molar Al:F 1.5:1) and 1 mL sulfuric acid for initial acidification. Section 2.3 reports 10% inoculum as w/v; that unusual basis is retained rather than silently changed to v/v. Biotic setups were triplicate. Uninoculated controls included an initial-pH negative control and an acid-adjusted comparator following the biotic pH. Dissolved elements were assayed by ICP-MS. The exact shaking speed and sample separation protocol for this assay are not resolved in Section 2.3.
Curated Evidence Points:
Sections 2.1-2.3, Table 2, Section 3.2 and Figure 3 report 94% of feed gallium in solution at the end of the 3% sludge assay, versus 77% in its acid-adjusted abiotic comparator. Figure 3 presents biotic means and SD; exact numeric SD is not transcribed here. These are leaching fractions, not an isolated-product recovery yield. The experiment remains laboratory scale despite the industrial origin of the sludge.
Section 3.2 reports 86% gallium leached within the first day and attributes rapid dissolution chiefly to low pH. It calls the abiotic controls simplified and explicitly requests replicate confirmation of microbial facilitation. Section 3.4 reports faster chemical processing at higher solids loading and discusses downstream precipitation prospectively; neither selective gallium recovery nor industrial bioleaching deployment follows from these data. The abstract's Al:Fe ratio conflicts with Al:F in the methods and results; the curated flask dose follows Table 2, not the abstract's 1.4:1 reactor/optimization value.

Sources & References

  1. chebi_gallium: ChEBI CHEBI:49631 — gallium atom
    https://www.ebi.ac.uk/chebi/CHEBI:49631 (accessed 2026-10-11)
  2. usgs2025: USGS (2025). Final 2025 List of Critical Minerals. Federal Register 90:50494-50497, document 2025-19813; gallium in the final commodity table.
    https://www.govinfo.gov/content/pkg/FR-2025-11-07/html/2025-19813.htm (accessed 2026-10-11)
  3. fritze2026: Fritze MT, Haubrich F, Otto A, Schippers A and Hedrich S (2026). Bioleaching of GaAs metal hydroxide sludge: a biohydrometallurgical alternative to conventional acid leaching. Frontiers in Microbiology 17:1807986. doi:10.3389/fmicb.2026.1807986.
    https://doi.org/10.3389/fmicb.2026.1807986 (accessed 2026-10-11)
  4. ncbi_thiooxidans: NCBI Taxonomy 930 — Acidithiobacillus thiooxidans, species rank
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=930&mode=Info (accessed 2026-10-11)

Curation History

Timestamp Curator Action Summary
2026-10-11T04:20:54Z Codex (GPT-6; Codex) record_creation Created a source-verified element record with final US 2025 criticality and laboratory sludge leaching evidence, retaining acid-only controls, provisional microbial enhancement and source-method uncertainties. Independent scientific review is a separate subsequent artifact.

Record source: data/records/gallium.yaml