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Nickel-based superalloy residue powders secondary resource

Source-designated industrial superalloy residue powders considered as secondary metal feeds, distinct from nickel or cobalt elements, certified alloy grades and recovered metal products. The accepted primary study tested three supplied stocks SAR-Ni 30167, SAR-In 32083 and SAR-Re 30168 within one resource family. Their feed compositions and leaching responses remain separate; no one stock represents all superalloys. Laboratory culture-filtrate experiments do not establish post-consumer provenance, industrial deployment or complete feed recovery.

Microbial & Biochemical Mechanisms (1)

Nickel and cobalt mobilization with biogenic acid and ferric filtrates

bioleaching Microbial

Associated Organisms: Acidithiobacillus thiooxidans (NCBITaxon:930)

Filtered culture media containing biogenic acid, ferric iron or both mobilized nickel and cobalt from three superalloy residue stocks. The acid-containing arms generally gave greater measured release than the less acidic ferric-only arm. Proton attack and ferric oxidation are proposed contributors, but differing initial pH and the absence of matched sterile chemical controls prevent a unique causal allocation or quantified microbial increment. The accepted result is laboratory dissolution into sampled liquor, not isolation of nickel or cobalt products.

Experimental Context & Analytical Limits:
AAS Ltd., Sheffield, UK supplied residues sourced from nickel- and cobalt-based superalloy bars. Exact commercial grades, prior service histories and manufacturing operations for each stock are not identified. Approximately 35 g per stock was ball-milled with stainless-steel balls at 300 rpm for ten minutes; the fraction below 250 micrometres was used. The Bangor Acidophile Culture Collection supplied source-named A. thiooxidans for Bio-acid production and an unresolved iron/sulfur oxidizing consortium for Bio-ferric and combined media. No strain accessions or consortium-member identities are reported. Culture production used mineral medium, sulfur and/or ferrous iron, initial pH adjusted to 1.8 with sulfuric acid, 30 degrees C and 130 rpm, followed by 0.2 micrometre filtration. The opening medium description and the subsequent arm-specific recipes are not completely aligned; no single inferred recipe is substituted for them. Comparisons used 1% w/v powder in 100 mL filtrate in 250 mL flasks at 30 degrees C and 130 rpm for seven days. Bio-acid and combined arms began at nominal pH 1.0, while Bio-ferric had 45 mM ferric iron at pH 1.8. Separate Bio-acid series tested 130, 200 and 270 rpm. Triplicate assays, evaporation replacement with sterile water, 0.22 micrometre leachate filtration, ICP-OES, pH, redox potential and ferrozine iron measurements are described. Sampling-loss correction is not explicit. The 0.1 M acid label in Table 3 is not an independent measurement of total biogenic acid or the fraction added chemically.
Curated Evidence Points:
Sections 2.1–2.4, Figures 1–5 and Tables 1–2 establish the three feed stocks, culture-filtrate preparation and observed Ni/Co release. A. thiooxidans is assigned only to the Bio-acid arm; the organism entry does not identify or causally assign the consortium arms. Bio-acid and combined media outperformed ferric-only medium under different initial acidities, especially for SAR-In 32083. Figure 5d shows only partial ferric reduction in that stock's ferric-only arm, contrary to the adjacent blanket statement of complete reduction for all three stocks. Acidolysis, passivation and secondary precipitation remain interpretations, not directly demonstrated surface phases or molecular pathways.
Section 3.1 acknowledges incomplete aqua-regia feed digestion, and Figure 2 confirms residual material. Equation 3 normalizes extraction using that digested feed concentration. Table 1's listed elemental means also sum above 1000 g/kg for SAR-Ni 30167 and SAR-Re 30168, so they are not a closed total-feed mass balance. These limitations prevent interpreting the source percentages as verified fractions of the entire original feed. XRF labels do not establish mineral species, alloy-grade identity or quantitative phase purity.
Figure 6 and Section 3.3 support faster early mobilization at 270 rpm for SAR-Ni 30167 and SAR-Re 30168: the source reports about 60% Ni and 70% Co after one day for the first stock, and about 60% Ni and 50% Co after two days for the second, on its own extraction denominator. This is not a universal endpoint advantage: SAR-In nickel performs worse at 270 rpm than 130 rpm by day seven, and SAR-Re cobalt at 130 rpm overtakes the faster-mixed arm later. The paper's broader statement that lower speed overtakes for both metals is not supported across every Figure 6 panel. The cited conversion of a ten-percentage-point SAR-Re cobalt increase to approximately 7.45 g/kg does not follow from Table 1's 65.30 g/kg cobalt inventory; it is not imported.
Figure 9 compares no-added-peroxide Bio-acid with 1, 3, 5 and 7 mL additions of nominal 30% peroxide at 270 rpm. Nickel release was not improved across the tested stocks, and SAR-Re cobalt also showed no general benefit. Some early cobalt values for the other stocks increased, without a consistent final advantage. Section 2.3 describes ten days but Figure 9 ends at seven; Section 3.4 mentions a 2 mL SAR-In condition absent from the specified and plotted series. The paper's volume-to-millimolar equivalence is not treated as a verified concentration conversion. No optimized peroxide recipe or general passivation-removal mechanism is accepted from these inconsistencies. No purified product, full economic/life-cycle assessment or industrial demonstration is reported; Section 3.5's favorable deployment claims remain proposals. Table 3 summarizes other studies, not independent controls for these feeds.
Context_only Source: ncbi_930
The authority confirms the species-level name and identifier used for the Bio-acid culture. It does not authenticate that stock, identify the separate consortium or establish the mechanism for every member of the species.

Sources & References

  1. constantin_2025: Constantin AD, Hall S, Pourhossein F, Farnaud S (2025). Strategies for Nickel and Cobalt Mobilisation from Ni-Based Superalloy Residue Powders Using a Sustainable and Cost-Effective Bioleaching Method. Processes 13(7):2157. DOI 10.3390/pr13072157; complete 21-page original, Sections 2–4, Tables 1–3 and Figures 1–9.
    https://doi.org/10.3390/pr13072157 (accessed 2026-10-14)
  2. ncbi_930: NCBI Taxonomy 930, current species name Acidithiobacillus thiooxidans. Species-level context only; not authentication of the source's unnamed culture or identification of its separate iron/sulfur-oxidizing consortium.
    https://www.ncbi.nlm.nih.gov/datasets/taxonomy/930/ (accessed 2026-10-14)

Curation History

Timestamp Curator Action Summary
2026-10-14T18:01:44.935187Z Codex (GPT-6; codex) CREATE Created the source-qualified secondary-resource owner; preserved conflicting conditions, incomplete balances, controls, null results and laboratory scope.

Record source: data/records/nickel-based-superalloy-residue-powders.yaml