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Arsenic element Critical Material

Arsenic (As), grounded by the neutral-atom ChEBI identifier. Arsenate, arsenite, gallium arsenide and metal hydroxide sludge are different chemical or resource entities. The US designation maps the listed arsenic commodity to this element without designating all arsenic-bearing wastes. Arsenic was retained in the final 2025 list despite proposed removal in the draft. The mechanism concerns co-mobilization from sludge in the same experiment curated for gallium, not an independent replication or an arsenic detoxification process.

Identifiers & Classification

System Identifier Label
CHEBI CHEBI:27563 arsenic 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)

Arsenic co-mobilization during hydroxide-sludge bioleaching

bioleaching Microbial

Associated Organisms: Acidithiobacillus thiooxidans (NCBITaxon:930)

Arsenic entered solution during acidic laboratory leaching of sludge with living sulfur-oxidizing Acidithiobacillus thiooxidans cultures. Similar final arsenic leaching in the acid-adjusted abiotic comparator does not establish a microbial enhancement. The observed process is co-mobilization, without a demonstrated arsenic redox reaction, detoxification or recovered arsenic product.

Experimental Context & Analytical Limits:
DSM 14887 type-strain cultures were adapted to 5% w/v sludge with aluminum; the taxon identifier resolves the species, not the strain. The GaAs-wafer-production hydroxide sludge was dried at 60 degrees C for 48 hours and mortar-homogenized. Table 1 reports 1.34% As by handheld XRF. Section 2.1 assumes arsenate associated with iron phases; it does not measure arsenic oxidation state in this assay. The curated 3% w/v experiment used 50 mL shake-flask setups, HBS medium, 1% elemental sulfur, initial pH 1.8, 30 degrees C and eight days. Table 2 gives 12.9 mM Al (molar Al:F 1.5:1) and 1 mL sulfuric acid initially. Section 2.3 labels the 10% inoculum w/v, an unresolved unusual basis. Biotic setups were triplicate; controls were uninoculated, either initially pH 1.8 or acid-adjusted to follow the biotic pH. Dissolved elements were measured by ICP-MS, without arsenic speciation. The exact shaking speed and sample separation protocol for this assay are not resolved in Section 2.3.
Curated Evidence Points:
Section 3.2 and Figure 3 report 68% of feed arsenic in solution after eight days in the 3% sludge biotic assay. The figure presents biotic means and SD, without numeric SD transcribed here. The authors associate arsenic release with dissolution of ferrihydrite; this is a host-dissolution interpretation, not evidence for microbial reduction of arsenate. Industrial feed provenance does not establish industrial operation of this laboratory process.
The same Section 3.2 reports 66% arsenic leaching in the acid-adjusted abiotic comparator and describes simplified controls requiring replicate confirmation. The small reported difference therefore does not establish arsenic-specific microbial benefit. Its statement placing initial 24% As at day 1 conflicts with Figure 3, which places that point at day 0; no initial value or derived arsenic rate is curated. Section 3.4 discusses subsequent chemical arsenic removal prospectively, not a tested microbial recovery or detoxification result. Methods and Table 2 specify Al:F, whereas the abstract says Al:Fe; this record follows the flask-specific Table 2 ratio.

Sources & References

  1. chebi_arsenic: ChEBI CHEBI:27563 — arsenic atom
    https://www.ebi.ac.uk/chebi/CHEBI:27563 (accessed 2026-10-11)
  2. usgs2025: USGS (2025). Final 2025 List of Critical Minerals. Federal Register 90:50494-50497, document 2025-19813; arsenic in the final commodity table and discussion of its retention following proposed draft removal.
    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
2026-10-11T04:21:03Z Codex (GPT-6; Codex) record_creation Created arsenic identity, dated final US 2025 criticality and sludge co-mobilization evidence, retaining similar abiotic extraction, no proven arsenic redox or recovery result and a source timing conflict. Independent scientific review is a separate subsequent artifact.

Record source: data/records/arsenic.yaml