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Uranium mine tailings secondary resource

Heterogeneous residual solids in uranium-mine tailings management areas, represented here by DT and RAT samples from two decommissioned Elliot Lake, Ontario sites. These are secondary mining residues, distinct from unprocessed uranium ore, individual uranium minerals, drainage water and purified elements. The original processing flowsheets and the expansions of the two sample-site abbreviations are not established by the curated study. Laboratory evidence concerns culture-associated metal solubilization and a separate resin screen; it does not establish industrial recovery or a resolved uranium extraction yield. No constituent-element criticality designation is inherited by these tailings.

Microbial & Biochemical Mechanisms (2)

Native-community-associated solubilization during acidic tailings treatment

bioleaching Microbial

DT-derived enrichment cultures were associated with release of uranium, thorium and rare-earth elements from DT and RAT tailings into solution. Iron-oxidizing growth and declining pyrite diffraction peaks support a biologically compatible oxidation process. Added sulfuric acid and the absence of a matched sterile leaching control prevent isolation of the microbial increment; neither a particular species nor an enzymatic route is demonstrated. Metal solubilization is distinct from recovered products.

Experimental Context & Analytical Limits:
Samples were collected from water-covered tailings management areas in June 2012. Mineralogical and elemental characterization shows mixed, quartz-rich solids containing sulfides, silicates and minor metal-bearing phases, not pure mineral substrates. Section 2.2.1 enriched 7 g fresh DT tailings in 100 mL distilled water for 22 weeks at 200 rpm; fresh RAT was unavailable. No sequence-resolved composition of the native inoculum was reported. Flask assays used 90 g tailings, 200 mL inoculum and 400 mL McCready medium at initial pH 2 with sulfuric acid, comparing 20, 30 and 40 degrees C. Methods describe 35 days, whereas Tables 5-6 extend to eight weeks. Duplicate stirred-tank assays for each material used 290 g tailings and 250 mL culture in 3 L total liquid at 30 degrees C and about 900 rpm; pH was readjusted to 2.0 +/- 0.1 after sampling. Air supply was about 12.5 L/min, present initially for DT but added after day 2 for RAT when dissolved oxygen fell. The stirred-tank results section calls these 30-day runs, Table 7 ends at week 4 and the abstract says 35 days; those descriptions are not silently equated. Chemical analytical triplicates are distinct from the duplicate reactors. This was a laboratory assay.
Curated Evidence Points:
Sections 2.1-2.2 and 3.2-3.4, Tables 5-7 and Figures 3-5 show solubilization in inoculated acidic assays. Table 7 reports week-4 stirred-tank LREE/HREE solubilization of 5.8%/54% for RAT and 14%/58% for DT; these are source-reported grouped dissolved fractions, not purified-product or microbial-attributable yields. Section 3.4 found at least 10^6 iron oxidizers per gram after DT treatment using most-probable-number growth tests, alongside reduced pyrite peaks. Neither observation establishes a particular organism's causal role.
Figures S1a-b and S2a-b support the approximate REE time-course patterns and show between-reactor variability, including the RAT HREE decline and recovery. Figure S2c instead shows DT uranium near 50% through the plotted period, while main Table 7 reports an increase from 53% to 89%. No correction resolving this conflict was located in the bounded search, so no reconciled DT uranium yield is adopted.
Section 3.3's page-12 prose assigns 42% to uranium and 85% to thorium for RAT at 30 degrees C, opposite the Th/U column values in Table 5. Endpoint descriptions also conflict. Growth-tube uninoculated controls in Section 3.4 are not sterile controls for the tailings leaching runs. ORP changes do not directly measure uranium valence, and XRD peak decline is not a quantitative phase balance. Differences in feed composition, particle size and aeration history limit direct cross-material comparisons. Economic and scale-up claims remain prospective, and a complete mass balance is not established here.

Abiotic resin sorption from composite tailings leachate

separation

Commercial ion-exchange resins removed different element groups from a composite tailings leachate in batch tests. This downstream operation is abiotic sorption after culture-associated leaching; the measurements establish solution depletion, not desorbed or purified recovered products.

Experimental Context & Analytical Limits:
Section 2.3 describes a combined DT/RAT stirred-tank leachate, whereas the end of Section 3.3 refers to collecting flask leachates for recovery studies. That provenance ambiguity is retained; results are not assigned to a single tailings sample. Twenty resins were screened at 1 g per 100 mL solution for 24 h at 150 rpm. Resin-with-water and solution-only method blanks were included. Six resins were subsequently tested at 0.5-2.5 g per 100 mL for 24 h. These were separate laboratory batch contacts, not a demonstrated sequential column flowsheet.
Curated Evidence Points:
Sections 2.3 and 3.5, Tables 8-9 and Figures 6-8 document leachate composition and selective solution removal. Table 9 reports TP272 removal of 94% Sc and 99% U, with 4% each LREE/HREE, and SP112 removal of 81% LREE and 65% HREE. These percentages refer to elements in the contacted composite solution, not initial-tailings inventory.
Pages 15 and 17-18 explicitly identify desorption or elution tests as remaining work. TP272 followed by SP112 is a proposed sequence; isolated-product purity, resin regeneration, integrated process yield and industrial feasibility were not demonstrated. The page-17 broad assertion of no thorium affinity for some resin types cannot replace the nonzero, resin-specific thorium values in Table 9.

Sources & References

  1. reynier2021: Reynier, Gagne-Turcotte, Coudert, Costis, Cameron and Blais (2021). Bioleaching of Uranium Tailings as Secondary Sources for Rare Earth Elements Production. Minerals 11:302. DOI 10.3390/min11030302; complete 21-page publisher article, Sections 2.1-2.3 and 3.1-3.5, Tables 2-9 and Figures 1-8.
    https://doi.org/10.3390/min11030302 (accessed 2026-10-15)
  2. reynier2021_supplement: Supplement to Reynier et al. (2021), Minerals 11:302; two pages, Figure S1 RAT and Figure S2 DT stirred-tank time courses. Figure S2c conflicts with the main article's DT uranium values.
    https://mdpi-res.com/d_attachment/minerals/minerals-11-00302/article_deploy/minerals-11-00302-s001.pdf (accessed 2026-10-15)

Curation History

Timestamp Curator Action Summary
2026-10-15T20:23:42.295616+00:00 Codex (GPT-6; Codex) CREATE Curated the full primary tailings experiment and supplement, preserving source conflicts, unresolved community and controls; separated abiotic resin sorption from product recovery.

Record source: data/records/uranium-mine-tailings.yaml