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Cemented tungsten carbide scrap secondary resource

Discarded hardmetal production components composed of tungsten carbide with cobalt or cobalt-nickel binder, represented by rolling-mill rollers and brazed cutting tips in the Chaika study. This manufactured secondary resource is distinct from pure tungsten carbide, a mineral species, tungsten mining tailings and metal grinding sludge. The sampled shapes and compositions do not define every hardmetal waste stream. No criticality designation or industrial deployment is inferred.

Microbial & Biochemical Mechanisms (2)

Culture and ferric-solution-associated hardmetal binder mobilization

bioleaching Microbial

Associated Organisms: Acidithiobacillus ferrooxidans (NCBITaxon:920)

A source-described bacterial ferric-sulfate solution was used in a continuously mixed hardmetal-scrap experiment. The authors report cobalt and nickel transfer into liquor and a tungsten-rich solid residue, with spent ferrous liquor routed to fermenters for biological ferric regeneration. This supports association with the reported culture-containing workflow. Ferric attack, electrochemical dissolution and mechanical abrasion also occur in the authors' process description; without matched controls it does not isolate a microbial enhancement or demonstrate a specific contact-mediated pathway.

Experimental Context & Analytical Limits:
Pages 125-128 describe production waste with Co binder in cutting tips and Co-Ni binder in rolling-mill rollers, mixed with the biological solution at a liquid-to-solid volume ratio of 1:1. This is not a mass loading. The apparatus is referred to a 2012 paper; its construction is not specified in this article. The working-solution criteria are ferric Fe above 4 g/L and pH below 4, with a seven-day time course. The source names Thiobacillus ferrooxidans and also an association of thionic bacteria; a verified pure culture is not established. Strain accession, stock provenance, inoculum density, nutrient recipe, incubation temperature, reactor volume, agitation rate, replicated leaching runs and analytical uncertainty are not supplied. Residue was decantation-washed and dried at 85 degrees C; that is a recovery preparation temperature, not the leaching temperature.
Curated Evidence Points:
Figure 1 and Table 2 identify the two scrap forms and different starting elemental compositions. Figure 2 shows increasing reported Co content over 168 hours, with the steepest rise in the first 24 hours and slower subsequent increase. Tables 3 and 4 separately describe residue and spent-liquor elemental composition, including residual Co in the solid and W in the liquor. These observations support incomplete partitioning rather than perfect separation. The paper does not resolve all subsequent products and time-course data into separate roller and cutting-tip experimental arms.
Figure 2 labels its Co axis as content in percent without specifying a fraction of initial feed Co, an absolute dissolved concentration or a mass-balance denominator. Tables 1-6 give relative elemental percentages; their analytical normalization and sample preparation are insufficiently described, and carbon is absent from the reported element lists. Neither the curve nor the liquor/residue compositions establish an extraction percentage, a WC purity or a recovered yield. The Figure 2 pH curve reaches approximately 4; the accompanying text highlights pH 1.5-3 and the working criterion is below 4. These descriptions are retained without treating pH as constant.
No matched sterile ferric-sulfate, acid-only, no-mixing or cell-free regeneration comparison is reported in the complete article. Page 126 explicitly states that the destruction mechanism is not finally established. Its proposed contact and indirect pathways and Equations 1-2 are explanatory hypotheses, not demonstrations of cell attachment, electron transfer, enzyme action or necessity. Culture abundance and iron-regeneration kinetics are not measured here. The experiment does not substantiate the introduction's environmental, economic or equipment advantages at industrial scale.
Page 127 reports predominantly hexagonal WC by DRON-4-07 phase analysis, but displays no original diffraction trace or quantitative phase fraction. Its particle-size range and mass-peak statement refer to a separate 2012 study, not an independently inspected size distribution in this article. Table 3 reports W at 95.395 percent and the discussion rounds this to 95.4 percent W; the conclusion instead calls the powder 95.2 percent WC purity. Relative elemental W abundance, especially without measured carbon, does not establish that phase-purity claim. No numerical WC purity is adopted.
The live authority lists the historical paper name as a homotypic synonym of Acidithiobacillus ferrooxidans. NCBITaxon:920 identifies a species, not the unaccessioned experimental stock or every member of the source-described bacterial association.

Chemical purification and reduction of the resulting leach liquor

recovery

The same workflow included chemical iron separation followed by alkaline hydrazine-hydrate reduction to a reported Co-rich powder containing nickel and other impurities. This downstream product preparation was not a microbial reduction. Product elemental composition and impurity comparisons do not establish whole-feed recovery, cobalt phase purity or an optimized industrial process.

Experimental Context & Analytical Limits:
Pages 127-129 compare aqueous ammonia iron precipitation at nominal pH 4, 5 and 11 with a sodium-fluoride route, followed by settling, filtration and hydrazine-hydrate treatment. The paper does not supply complete reagent doses, isolated product masses, replication, sampling-adjusted metal balance or independent phase characterization of the reported cobalt powders. These are downstream treatments of the earlier liquor, not additional bioleaching experiments.
Curated Evidence Points:
Tables 5-6 and Figure 3 document differing precipitate/powder compositions. Table 6 reports relative Co contents of 70.089, 87.831 and 89.843 percent for the pH 4, 5 and 11 ammonia routes, and 80.098 percent for sodium fluoride. These are source-reported elemental contents, not percentages of feed cobalt recovered. Table 5 reports 44.597 percent Co in the pH 11 iron-separation precipitate, supporting co-precipitation as a loss pathway without quantifying its mass. The authors therefore favor pH 5 despite higher relative Co content in the pH 11 final powder.
Page 129 discusses pH 4.5 where Table 6 and Figure 3 label pH 5; it gives 1.27 percent Fe for the sodium-fluoride powder whereas Table 6 gives 1.373 percent. The concluding 89.8 percent Co value corresponds to the pH 11 column, not the recommended pH 5 column. Figure 3 omits Ni although Table 6 includes it. Equation 7's printed sodium-iron-fluoride stoichiometry is not balanced and is not adopted. These inconsistencies prevent treating the headline purity, chosen pH and chemical equation as a single validated recovery specification.

Sources & References

  1. chaika2013_hardmetal: Chaika, Derbasova and Gavrish (2013), Research division of tungsten carbide and cobalt as a result of microbiological waste destruction of tungstencobalt waste. Visnyk NTUU KPI, Mechanical Engineering 3(69), 125-130. Complete Russian original, Figures 1-3, Tables 1-6, Equations 1-8. Publisher portal posting date 2014-01-07 differs from printed issue year 2013. Publisher-declared DOI 10.20535/2305-9001.2013.69.29004 returned 404 at both DOI resolver and Crossref on the access date; the official article/PDF is accessible.
    https://journal.mmi.kpi.ua/old/article/view/29004 (accessed 2026-10-12)
  2. ncbi_ferrooxidans: NCBI Taxonomy 920, Acidithiobacillus ferrooxidans; Thiobacillus ferrooxidans is a homotypic synonym. Species nomenclature only, without authentication of the experimental culture.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=920&mode=Info (accessed 2026-10-12)

Curation History

Timestamp Curator Action Summary
2026-10-12T01:56:58Z Codex (GPT-6) CREATE Created a distinct cemented tungsten carbide scrap resource from the complete original Chaika study and fresh species authority. Separated culture/ferric-associated binder mobilization from chemical powder preparation and retained missing controls, unresolved denominators, source inconsistencies, incomplete phase evidence and DOI access limits.

Record source: data/records/cemented-tungsten-carbide-scrap.yaml