Electrical-cable recycling residues secondary resource
Metal- and polymer-bearing residual material generated during physical recycling of electrical cables. The accepted experiment uses the low-density fraction remaining after knife milling and two-step gravity separation of end-of-life vehicle cables, rather than intact cable, a high-grade copper concentrate, printed circuit boards or undifferentiated vehicle shredder residue. This process-defined secondary feed is not a mineral species or elemental copper commodity. One laboratory study compares inoculated and bactericide-treated acidic ferric leaching, with only limited evidence for microbial enhancement; neither isolated copper production nor industrial deployment is demonstrated. Constituent-metal criticality is not inherited.
Microbial & Biochemical Mechanisms (1)
Limited culture-associated contribution during acidic ferric leaching
bioleaching
Microbial
An adapted mixed acidophilic culture was tested alongside thymol-treated chemical controls during copper dissolution from real cable-recycling residue. Chemical ferric oxidation dominated the observed kinetics; regeneration of ferric iron by the culture was proposed but too slow to establish a strong general microbial benefit. The source reports somewhat shorter normalized copper-leaching times in selected inoculated arms, while a separate synthetic-feed comparison showed no time advantage. These results do not establish a species-specific causal effect or a feed-to-product copper recovery yield.
Experimental Context & Analytical Limits:
Methods 2.1–2.4 (postprint p.2) describe a below-5-mm low-density vehicle-cable residue containing 4.9% Cu and 0.6% Al, predominantly plastic fragments and liberated metal wires. Copper/aluminium composition was measured after analytical ignition and digestion; ignition at 850 degrees C was not the leaching pretreatment. The Sofia University of Mining and Geology culture initially contained source-named Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans, with A. ferrooxidans described as prevalent. Strains, final community composition and member-specific activities are unresolved. Adaptation used iron-containing 9K medium with added Cu and Al. Fourteen tests used nominal 9% pulp density, 45–55 g solid and 450–550 mL solution in a stated 0.5-L jacketed reactor at 700 rpm, sulfuric-acid control at pH 1.9 and 21, 35 or 50 degrees C. The stated mass/volume ranges and 9% convention are retained without inferring a unique working charge. All abiotic tests received thymol, whose dose and independent chemical effects are unspecified. Tests 3, 4 and 13 also contained inoculum before bactericide addition; other abiotic arms used ferric sulfate. Tests 13–14 used analytical Cu/Al with silica replacing plastics and are separate synthetic-feed controls. Liquor metals were assayed by atomic absorption/ICP-OES, Fe(II) by dichromate titration and Fe(III) by difference; endpoint residues were also digested. Replicated reactor runs and quantitative uncertainty estimates are not reported.
Methods 2.1–2.4 (postprint p.2) describe a below-5-mm low-density vehicle-cable residue containing 4.9% Cu and 0.6% Al, predominantly plastic fragments and liberated metal wires. Copper/aluminium composition was measured after analytical ignition and digestion; ignition at 850 degrees C was not the leaching pretreatment. The Sofia University of Mining and Geology culture initially contained source-named Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans, with A. ferrooxidans described as prevalent. Strains, final community composition and member-specific activities are unresolved. Adaptation used iron-containing 9K medium with added Cu and Al. Fourteen tests used nominal 9% pulp density, 45–55 g solid and 450–550 mL solution in a stated 0.5-L jacketed reactor at 700 rpm, sulfuric-acid control at pH 1.9 and 21, 35 or 50 degrees C. The stated mass/volume ranges and 9% convention are retained without inferring a unique working charge. All abiotic tests received thymol, whose dose and independent chemical effects are unspecified. Tests 3, 4 and 13 also contained inoculum before bactericide addition; other abiotic arms used ferric sulfate. Tests 13–14 used analytical Cu/Al with silica replacing plastics and are separate synthetic-feed controls. Liquor metals were assayed by atomic absorption/ICP-OES, Fe(II) by dichromate titration and Fe(III) by difference; endpoint residues were also digested. Replicated reactor runs and quantitative uncertainty estimates are not reported.
Curated Evidence Points:
Support
Source:
lambert2015
Tables 1–2 and Figure 7 (pp.3–5) compare actual-residue tests 4 and 10 at 35 degrees C, initial Fe(III) 1.9 g/L, 10% inoculum and air injection of 3 mL/min; total Fe differs slightly, 10.2 versus 10.1 g/L. The source reports time to its 90% normalized copper endpoint of 69 h for thymol-treated test 4 and 50 h for living-culture test 10, with initial rates of 65 and 102 mg/L/h. These are source-reported arm values without replication-based significance, not proof that all differences are microbial. Table 2 defines endpoints at 90%, while Section 3.2 defines the percentage as recovered Cu mass divided by total Cu mass. No isolated copper-metal product is reported.
Partial
Source:
lambert2015
Sections 2.2–2.3 specify Cu/Al-containing adaptation liquor and substantial inoculum fractions, including 100% culture liquor in test 11. Section 3.5 gives different Cu/Al concentrations for the separate fermenter-rate assessment. The manuscript does not clearly document subtraction of inoculum-derived copper from each plotted residue-extraction curve or provide a complete initial-liquor/feed/final-liquor/residue balance. The kinetic derivation also assumes zero initial dissolved Cu. Therefore reported normalized extraction is retained as the authors' endpoint, not independently established recovery of that fraction of cable-derived copper. The high-inoculum 23 h versus 36 h comparison is not used as an uncontested biological effect.
Support
Source:
lambert2015
Sections 3.4–3.5, Figures 3–10 and Tables 1–2 show substantial chemical dissolution and a limited biological contribution. Iron-free abiotic test 2 reached only about 84% of the source-normalized copper endpoint after seven days; added ferric iron accelerated leaching in both inoculated and chemical arms. In synthetic tests 13 and 14, Table 2 reports the same 32 h to 90% for both arms; Section 3.5 explicitly states no microbial improvement there. Their initial ferric concentrations differ, 0.7 versus 1.2 g/L in Table 1, so this is not an exact matched-dose test or direct evidence for the actual polymer-bearing residue. Ferric accumulation after copper dissolution in Figure 8 supports possible regeneration but not a species-resolved rate mechanism.
Partial
Source:
lambert2015
Section 3.6 and Figure 13 (p.7) show faster dissolution at higher temperature even in nominally biotic test 12 at 50 degrees C, where the text reports no detected bacteria and no biological mechanism. That arm is not assigned a microbial recovery result. Figure 11's caption, displayed legend and the text's test-number assignments disagree, preventing confident reassignment of individual cell-count curves. Culture persistence, oxygen sufficiency and inhibition by plastics are discussed as alternatives, but the paper does not isolate the cause of the low ferric-regeneration performance.
Partial
Source:
lambert2015
Table 2 and Section 3.7 report lower measured acid consumption for actual-residue test 10 than test 4, 1.21 versus 1.49 mol sulfuric acid per mol dissolved Cu at the 90% endpoint; the explanation remains unresolved. These ratios inherit the copper-denominator limitation. Several source labels conflict: Figure 9's legend and Section 3.5 identify tests 5 and 11, whereas its caption says tests 6 and 13; Figure 8's caption lists a different test set from its legend. Table 2 and Section 3.7 give test 11 acid consumption 0.79, whereas the conclusion gives 0.93. These discrepancies are not silently reconciled, and the repository postprint is not assumed identical to an uninspected final typeset version. No activation-energy fit or caption-only assignment is imported as a uniquely demonstrated microbial mechanism.
Sources & References
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lambert2015: Lambert, F., Gaydardzhiev, S., Léonard, G., Lewis, G., Bareel, P.-F. and Bastin, D. (2015). Copper leaching from waste electric cables by biohydrometallurgy. Minerals Engineering 76:38–46. DOI 10.1016/j.mineng.2014.12.029. Complete nine-page ORBi publisher postprint marked Article in Press, Sections 2–4, Tables 1–3 and Figures 1–13 inspected. Its numbered pages 1–9 are used for locators; several captions and conclusion values conflict with the displayed tables/legends.
https://doi.org/10.1016/j.mineng.2014.12.029 (accessed 2026-10-15)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-15T08:30:47.539962+00:00 |
Codex (GPT-6; Codex) | CREATE | Created distinct cable-recycling residue identity with qualified mixed-culture and chemical comparison, explicit synthetic-arm exclusion, weak/null effects, source-label conflicts and inoculum-dependent denominator limits. |
Record source: data/records/electrical-cable-recycling-residues.yaml