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Gold-mine tailings secondary resource

Processing-derived residual material from gold production, distinct from unprocessed gold ore, elemental gold, individual mineral species and isolated rare-earth products. The curated experiment concerns one air-dried, sieved batch obtained from the Mouteh Gold Factory tailings dam. It supports qualified chemical pretreatment and culture-associated praseodymium, cerium and europium mobilization at laboratory scale; its composition and behavior do not define all gold-mine tailings. No criticality designation is inherited from constituents.

Microbial & Biochemical Mechanisms (2)

Chemical oxalic-acid pretreatment of a mixed gold-tailings feed

other

An abiotic oxalic-acid stage preceded the bacterial-culture assay and reportedly dissolved some iron while the three assayed rare-earth elements remained below detection in its filtrate. This is a chemical pretreatment observation, not microbial oxalate production, complete iron removal or isolated-metal recovery.

Experimental Context & Analytical Limits:
Fereydouni et al. (2025), Methods and Conclusion: tailings were air dried and sieved through mesh 200 to less than 75 micrometres. The Conclusion and abstract specify 2 M oxalic acid, 90 degrees C and a liquid-to-solid ratio of 60 mL/g for 6 h; Methods independently specifies 500 rpm, 6 h, a heated flask sealed with foil and subsequent vacuum filtration, but omits the acid concentration, temperature and liquid-to-solid ratio. The bioleaching solid loading is not this chemical-stage ratio. Rinsing, drying and residual oxalate carryover into the subsequent culture stage are not detailed. Only one tailings batch was studied.
Curated Evidence Points:
Methods Characteristics GMT (p. 2), Results Pretreatment with oxalic acid (p. 3) and Conclusion (p. 10) identify the processing waste and chemical stage. The authors report at most 20% iron dissolution and Pr, Ce and Eu below 0.01 mg/L in the oxalic-acid leachate. Below detection is not zero and does not by itself close a rare-earth mass balance or establish quantitative retention in the residue.
Figure 3 and pp. 5–6 compare source-assigned quartz, clinochlore, muscovite, albite and gypsum peaks. Prose first says clinochlore and gypsum were removed, then narrows this to reduced peaks and explicitly disclaims complete contaminant removal. Figure 3 also labels hydrogen oxalate hydrate after pretreatment. These qualitative patterns do not quantify phase abundance, establish a particular rare-earth host or prove that iron removal alone caused subsequent extraction changes. Figures 4–6 provide FTIR/SEM/EDX context rather than a phase-specific dissolution balance.

Sulfur-oxidizing culture-associated rare-earth mobilization after pretreatment

bioleaching Microbial

Associated Organisms: Acidithiobacillus thiooxidans (NCBITaxon:930)

A living A. thiooxidans culture was used to condition sulfur-containing medium before addition of the mixed tailings. The paper reports higher dissolved Pr, Ce and Eu extraction endpoints for oxalic-acid-pretreated than untreated tailings. Acid generation is a plausible culture contribution, but omitted control data, incomplete loading information and inconsistent growth descriptions prevent a quantified microbial advantage, a unique molecular mechanism or a demonstrated synergistic interaction from being inferred.

Experimental Context & Analytical Limits:
Methods pp. 2–3 attributes strain PTCC 1717 to IROST, Tehran; the species identifier is verified at NCBI but does not authenticate the experimental stock or strain. Growth medium is listed as elemental sulfur 5 g/L, (NH4)2SO4 2 g/L, K2HPO4.3H2O 0.25 g/L, MgSO4.7H2O 0.25 g/L and KCl 0.1 g/L. Propagation used 10% (v/v) inoculum at 30 degrees C and 140 rpm. The two-step assay separately specifies 100 mL medium in 250 mL flasks, 2% (v/v) inoculum described as 10^8 cells/mL, 30 degrees C, 140 rpm and seven days of leaching. Results chooses culture day 12 for tailings addition, whereas Methods calls the addition the end of logarithmic growth and Results/Conclusion describe its onset; no harmonized growth-stage interpretation is imposed. Bioleaching solids mass/pulp density, pretreatment-residue mass and assay-specific feed composition, filtration cutoff, replicate number and error-bar definition are not supplied in the inspected article. Hemocytometer counts are not viability or CFU measurements. Filtered liquor was analyzed by ICP-OES; water could be added to compensate evaporation.
Curated Evidence Points:
Results Extraction of metals (p. 4) and original Figure 2 (p. 5) report increased solution-extraction endpoints between days 3 and 7 in the pretreated culture assay: Pr 57% to 76%, Ce 31% to 46% and Eu 5% to 14%. Figure 2 includes a seven-day untreated-feed culture comparator with lower bars. These are the authors' reported percentages, not curator-recalculated yields. Equation 1 (p. 3) defines the numerator as leachate concentration Cs (mg/L) times solution volume Vs (L), divided by feed content Cf (mg/g) times feed mass Mf. It does not measure an isolated product. The publication does not provide the solid loading or post-pretreatment inventories needed to reconstruct the denominator and closed mass balance across both stages.
The original Figure 2 bar heights and Results compare pretreated with untreated bacterial cultures. Abstract reports increases of 24.4%, 14.4% and 9.1% for Pr, Ce, Eu; Results rounds these to 24, 14, 9%. The plotted comparison is consistent with differences in extraction percentage points, not established relative-percent gains or a factorial synergy estimate. The Results says uninoculated controls under the same conditions gave near-zero extraction but explicitly omits their data from Figure 2; numerical control trajectories, uncertainties and pH/sulfuric-acid matching are not provided. This is an asserted control result, not independently reconstructable evidence that biological chemistry outperforms matched abiotic acid. Dead-cell, cell-free-liquor and acid-matched comparisons are not shown.
Figure 1a (p. 4) begins with a cell-count point around 4 x 10^8 cells/mL and declines over a 14-day axis, whereas p. 3 states an initial 4 x 10^6 cells/mL and describes maximum growth/log-phase onset at day 12. Figure 1b spans seven days, with pH approximately 0.8 to 0.6 and back to 0.8, not a plotted 3.5-to-0.7 preculture trajectory. The graph/text do not unambiguously align propagation, addition and assay times. Hemocytometry does not establish the prose assertion that cells eventually died. Sulfate/pH/Eh observations are compatible with changing medium chemistry, but do not demonstrate a specific metabolic flux or iron oxidation-state ratio.
Methods p. 2 reports bulk ICP-OES feed concentrations in mg/kg, including Fe 322743, Al 527, Pr 100, Eu 213 and Ce 112; p. 5 later repeats 322743 for Fe with an incompatible mg/L label. Figure 6 EDX tables are explicitly Wt.% and list Fe 15.65, 5.12, 1.71 across stages, while p. 6 calls these v/v. The middle two-entry table sums to 89.47%, and EDX Al values 84.35–98.29% differ greatly from the stated bulk Al assay. These EDX values cannot substitute for bulk feed inventories, absolute iron removal or a closed mass balance. Figure 2 plots Fe on a Recovery(%) axis, whereas p. 4 describes an iron content falling to 1%; those quantities are not equated here.
Figure 7/Table 1 (p. 9) present fitted shrinking-core comparisons, not direct rate-limiting-step measurements. The text on p. 10 gives Eu conventional chemical-reaction R-squared as 0.9168, but Table 1/Figure 7e assign 0.9168 to diffusion and 0.9611 to chemical reaction. Its claim that sulfate-adjusted models predict better conflicts with the lower reported R-squared values, including 0.4012 for Ce and 0.2617 for Eu. These fits do not establish a unique mechanism. Single-batch shake-flask data and qualitative surface images provide no isolated-REE product, gold-recovery result, demonstrated industrial deployment or universal gold-tailings performance.
NCBI Taxonomy 930 resolves to Acidithiobacillus thiooxidans at species rank. This supports the stated species mapping only; PTCC 1717 remains the publication's culture-collection attribution and is not independently authenticated by the species record.

Sources & References

  1. fereydouni2025: Fereydouni, H., Naseri, T. and Mousavi, S.M. (2025). Synergistic recovery of Pr, Eu, and Ce from gold mine tailings using bioleaching and oxalic acid pretreatment. Scientific Reports 15:4478. DOI 10.1038/s41598-025-88594-0; published 6 February 2025. Complete 12-page publisher article, Figures 1–7, Table 1 and Methods/Results/Conclusion inspected; no supplementary-file link identified in complete publisher HTML or PMC XML. Underlying data available from corresponding author on reasonable request.
    https://doi.org/10.1038/s41598-025-88594-0 (accessed 2026-10-12)
  2. ncbi_thiooxidans: NCBI Taxonomy 930: Acidithiobacillus thiooxidans, species; current official taxonomy XML inspected on 12 October 2026.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=930 (accessed 2026-10-12)

Curation History

Timestamp Curator Action Summary
2026-10-12T09:15:16.946343+00:00 codex (GPT-6; codex) CREATE Created a distinct gold-production tailings resource with separately scoped chemical pretreatment and culture-associated REE mobilization, preserving incomplete controls, inconsistent quantities and timelines, and laboratory/solution-extraction limits.

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