Electroformed copper-silver manufacturing scrap secondary resource
Defective electroformed copper components retaining an inner silver-bearing conductive coating from manufacture on expendable wax mandrels. The studied tube-shaped rejects had incomplete copper deposition or uneven wall thickness. This manufacturing-derived secondary resource is distinct from elemental copper or silver, printed circuit boards, electroplating sludge and multilayer beverage packaging. Its selected composition does not define all electroforming waste or confer a jurisdictional criticality designation.
Microbial & Biochemical Mechanisms (2)
Culture-associated ferric regeneration and copper solubilization
bioleaching
Microbial
Associated Organisms:
Acidithiobacillus ferruginosus (NCBITaxon:3063951)
Growing iron-oxidizing acidophiles regenerated ferric iron in laboratory leaching systems, supporting copper dissolution from defective Cu/Ag tubes while leaving a silver-rich residue. The article's direct two-step label describes cultures present with the feed after pre-growth; it does not demonstrate direct cellular electron transfer from metallic copper. A pure CF3 flask, mixed-culture flask and adapted-consortium reactor are different experimental systems, not replicated treatments.
Experimental Context & Analytical Limits:
Methods 2.1 describes copper electrodeposition over Ag-painted wax mandrels; defective components had approximately 500 micrometre Cu walls and a 24-30 micrometre inner Ag layer. The Discussion reports 94.4 wt.% Cu and 5.6 wt.% Ag for this feed, without an independently reconstructed bulk assay denominator. Bangor's Acidophile Culture Collection supplied CF3 and the Table 1 ten-member inoculum. The sole organism CURIE below gives current species context for the separately tested CF3 culture, not every member or active species in the consortium. Table 1 also names A. ferrooxidans, A. ferrivorans, A. ferridurans, A. ferriphilus, A. ferrianus, Sulfobacillus thermosulfidooxidans, Leptospirillum ferrooxidans, L. ferriphilum and Sulfoacidibacillus ferrooxidans; these are source labels, not independently authenticated strain assignments. Sterile basal salts and trace elements at initial pH 1.7 contained 20 mM Fe(II). After its oxidation during pre-growth, ethanol-treated tubes were added: 19.64 g for CF3 and 18.98 g for the consortium in 0.7 L, approximately 2.8 and 2.7% pulp density. Methods 2.3 gives about 23 degrees C, 220 rpm and automated pH 1.9 control with 1 M sulfuric acid; Figures 2-3 instead say 130 rpm, and the abstract says 22 degrees C. Leachate replacement retained 70 mL inoculum before replenishment to 0.7 L. The reactor used the prior flask consortium, 19.83 g feed, a 2 L vessel, 32 degrees C, 130 rpm, approximately 1 L/min air, pH 1.9 and medium replacement after seven leaching days. A single uninoculated flask control ran at 25-28 degrees C and 220 rpm for 75 days. Dissolved Cu was measured by ICP-OES after 0.22 micrometre filtration; ferrozine assays measured soluble Fe species.
Methods 2.1 describes copper electrodeposition over Ag-painted wax mandrels; defective components had approximately 500 micrometre Cu walls and a 24-30 micrometre inner Ag layer. The Discussion reports 94.4 wt.% Cu and 5.6 wt.% Ag for this feed, without an independently reconstructed bulk assay denominator. Bangor's Acidophile Culture Collection supplied CF3 and the Table 1 ten-member inoculum. The sole organism CURIE below gives current species context for the separately tested CF3 culture, not every member or active species in the consortium. Table 1 also names A. ferrooxidans, A. ferrivorans, A. ferridurans, A. ferriphilus, A. ferrianus, Sulfobacillus thermosulfidooxidans, Leptospirillum ferrooxidans, L. ferriphilum and Sulfoacidibacillus ferrooxidans; these are source labels, not independently authenticated strain assignments. Sterile basal salts and trace elements at initial pH 1.7 contained 20 mM Fe(II). After its oxidation during pre-growth, ethanol-treated tubes were added: 19.64 g for CF3 and 18.98 g for the consortium in 0.7 L, approximately 2.8 and 2.7% pulp density. Methods 2.3 gives about 23 degrees C, 220 rpm and automated pH 1.9 control with 1 M sulfuric acid; Figures 2-3 instead say 130 rpm, and the abstract says 22 degrees C. Leachate replacement retained 70 mL inoculum before replenishment to 0.7 L. The reactor used the prior flask consortium, 19.83 g feed, a 2 L vessel, 32 degrees C, 130 rpm, approximately 1 L/min air, pH 1.9 and medium replacement after seven leaching days. A single uninoculated flask control ran at 25-28 degrees C and 220 rpm for 75 days. Dissolved Cu was measured by ICP-OES after 0.22 micrometre filtration; ferrozine assays measured soluble Fe species.
Curated Evidence Points:
Results 3.1-3.3 and Figures 2-4 document rising dissolved Cu, cell counts and high redox potential during inoculated leaching. Reported cumulative Cu solubilization was about 95% for CF3 over 78 days, 99.2% for the consortium flask over 59 days and 99.6% for the adapted reactor over 12 leaching days. Pre-growth precedes those leaching durations. CF3's result is 94.7% in the abstract and 95.2% in Results 3.1; the discrepancy is retained rather than selecting an exact value. The uninoculated control released 5.3% in 75 days and retained predominantly Fe(II), supporting culture-associated ferric regeneration under the tested conditions rather than an exclusive biological dissolution chemistry.
The control was not matched to the reactor's temperature, aeration or adaptation and did not maintain an equivalent abiotic ferric supply. No independently replicated leaching vessels or inferential statistical comparison are described in Methods 2-3; time-course points and n values for redox readings are not biological replicates. Faster reactor dissolution therefore cannot be assigned specifically to adaptation, community composition, temperature or aeration. CF3 plateaued near 42% before medium replacement; Cu inhibition is an interpretation rather than an isolated dose-response experiment. Fresh medium and continual sulfuric-acid dosing are material process inputs.
Results 3.2-3.3 and Figure 5 show changes in genus-level sequence-read proportions and cultured isolates resembling A. ferridurans and L. ferriphilum. These observations do not isolate each member's causal contribution or distinguish viable from dead-cell DNA. The abstract gives final Leptospirillum abundance as 59%, whereas Results 3.3 says 50.0%; the discrepancy remains unresolved. Figure 5 is not used to infer an independent exact percentage. No sequence accession is supplied in the inspected main article. The missing supplementary images limit verification of apparatus and abiotic-residue microscopy but do not remove the main-text control data.
Results 3.5 and Figure 7 show collected Ag-rich residue with local EDS values of 92.6% Ag, 7.2% Cu and 0.2% Fe. This is an incompletely purified residual fraction, not a measured whole-feed Ag recovery yield or evidence of microbial silver reduction. Local EDS and photographs do not establish bulk purity, metal mass balance, product specification or closed-loop manufacturing performance. Laboratory feed manufacture and use do not establish industrial deployment or verified economic and environmental advantage.
Context_only
Source:
ncbi_cf3_species
The current NCBI species label and CF3 type-strain annotation support using A. ferruginosus as taxonomic context. The paper's A. ferrooxidans and Table 1 parenthetical ferruginosis are preserved as historical source naming; the species CURIE does not independently identify the exact laboratory stock or establish a consortium member's role.
Context_only
Source:
ncbi_cf3_biosample
The public CF3 sample is assigned to A. ferruginosus; its linked project retains an A. ferrooxidans strain CF3 title. This supports a nomenclature distinction and is not a sequence deposit for the leaching experiment.
Chemical iron removal followed by copper electrowinning
recovery
A separate electrochemical operation deposited copper from selected bioleachates on a copper-foil cathode. Prior iron precipitation improved the reported electrowinning performance but discarded part of the dissolved copper. Neither stage is demonstrated microbial copper biomineralization, and its solution-based yield is not whole-feed recovery.
Experimental Context & Analytical Limits:
Methods 2.4 used 200 mL leachate in a stirred beaker at about 22 degrees C and 300 rpm, 20 mA/cm2, a 5 by 5 cm Cu-foil cathode and an IrO2-Ta2O5-coated Ti anode for up to five hours. Unamended liquor at pH 1.9 contained 20 mM Fe; amended liquor was raised to about pH 4 with 1 M KOH and filtered at 0.22 micrometres to remove precipitated iron. The tested leachates contained 13.7-21.7 g/L Cu; these concentrations do not describe every collected fraction. Sampling ICP measurements tracked residual dissolved Cu, and SEM-EDS examined deposited material.
Methods 2.4 used 200 mL leachate in a stirred beaker at about 22 degrees C and 300 rpm, 20 mA/cm2, a 5 by 5 cm Cu-foil cathode and an IrO2-Ta2O5-coated Ti anode for up to five hours. Unamended liquor at pH 1.9 contained 20 mM Fe; amended liquor was raised to about pH 4 with 1 M KOH and filtered at 0.22 micrometres to remove precipitated iron. The tested leachates contained 13.7-21.7 g/L Cu; these concentrations do not describe every collected fraction. Sampling ICP measurements tracked residual dissolved Cu, and SEM-EDS examined deposited material.
Curated Evidence Points:
Results 3.4 and Figure 6 report 89% Cu recovery from unamended liquor in four hours with 60-66% current efficiency, versus near-complete solution depletion in approximately 3.3 hours after iron removal and 80-92% current efficiency during active plating. The source alternates greater-than-99%, 99.9% and 99.99% wording; this record does not turn those rounded statements into a more precise reconstructed yield. Current efficiency subsequently fell as dissolved Cu was depleted.
Raising pH removed more than 99.99% of iron as reported, but also co-precipitated 6-19% of the already solubilized Cu. Electrowinning recovery is conditional on the remaining liquor and cannot be applied to the original scrap without those losses and other stage balances. Figure 8 and Results 3.5 give local EDS Cu contents of 98.5-99.9% on the recovered sheet. A starting Cu-foil cathode, local elemental measurements and no reported net deposited-mass balance prevent treating these values or the sheet dimensions as a validated bulk product yield or certified purity.
Sources & References
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pakostova2023_electroformed: Pakostova and Herath (2023). A Bioleaching Process for Sustainable Recycling of Complex Structures with Multi-Metal Layers. Sustainability 15(19):14068. DOI 10.3390/su151914068; published 22 September 2023. Main Methods 2.1-2.6, Results 3.1-3.5, Discussion, Table 1 and Figures 1-8 inspected. Supplementary Figures S1-S4 were not acquired; their main-text captions are not substituted for visual inspection.
https://doi.org/10.3390/su151914068 (accessed 2026-10-11) -
ncbi_cf3_species: NCBI Taxonomy 3063951, Acidithiobacillus ferruginosus, species rank and effective name; CF3 listed as type strain. Current label differs from the experimental paper's A. ferrooxidans CF3 naming.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=3063951&mode=Info (accessed 2026-10-11) -
ncbi_cf3_biosample: NCBI BioSample SAMN14556242, sample AFE_CF3, strain CF3, current organism Acidithiobacillus ferruginosus. Taxonomic context, not authentication of the experimental culture used in the 2023 leaching study.
https://www.ncbi.nlm.nih.gov/biosample/SAMN14556242 (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T16:13:14.036657Z |
Codex (GPT-6; Codex) | CREATE | Created the distinct defective electroformed Cu/Ag component resource, scoped culture-associated ferric leaching and separate electrowinning, retaining CF3 nomenclature, source discrepancies, unmatched controls, downstream Cu loss, local-EDS limitations and unavailable supplement. |
2026-10-11T16:22:11.028471Z |
Codex (GPT-6; Codex) | EDIT | Addressed independent review F1 by removing the incorrect assertion that Figure 5 supports the Results 50.0% Leptospirillum value. Retained the abstract 59% versus Results 50.0% discrepancy without inferring an independent exact percentage from the graph. |
Record source: data/records/electroformed-copper-silver-manufacturing-scrap.yaml