Electric-arc-furnace dust secondary resource
Zinc-bearing dust generated by electric-arc-furnace steelmaking, represented here by two actual dusts supplied by an unnamed steelmaking company. This process-defined secondary resource is distinct from cast-house dust, blast-furnace flue-gas dust, steelmaking slag, zinc ore and elemental zinc. The two samples do not define a universal composition. No elemental identifier or criticality designation is assigned to the dust.
Microbial & Biochemical Mechanisms (2)
Zinc mobilization by sulfur-oxidizing culture-derived acid
bioleaching
Microbial
Associated Organisms:
Acidithiobacillus thiooxidans (NCBITaxon:930)
Acidithiobacillus thiooxidans DSM 504 produced an acidic sulfur-containing culture liquid that was filtered before contact with the EAF dusts. The evidence supports indirect biogenic-acid dissolution of zinc under specified laboratory conditions. The organism generated the lixiviant; living cells were not intentionally retained in the leaching stage. Preferential zinc mobilization over iron was strongly feed- and condition-dependent and is not an isolated-metal recovery yield.
Experimental Context & Analytical Limits:
Methods 2.1-2.3 describe two EAF dusts from a steelmaking company, without naming its location or defining their mineral phases. Table 4 reports 99.8% dry mass in both, with Zn 161000 and 390000 mg/kg dry mass in Dusts 1 and 2 respectively. Drying at 105 degrees C refers to dry-mass characterization; whole-feed sterilization or pretreatment is not stated. The named culture was grown in basal salts, elemental sulfur and 0.02 g/L yeast extract. Acid production used a 3-L working-volume stirred reactor at 30 degrees C, 160 rpm and 75 L/h air, with 20 g/L sulfur and 100 mL inoculum. After each two-week production cycle, fresh medium and sulfur replaced the contents and 100 mL from the previous culture reinoculated the next cycle. The authors call this fed-batch operation. Culture liquid passed through a 0.22-micrometre filter before duplicate 50-mL leaching assays. Assays varied 50-100 g/L dust, 30-50 degrees C and 2 minutes to 24 hours; leaching mixing speed is not given. The reactor's 160 rpm is not assigned to these separate leaching assays.
Methods 2.1-2.3 describe two EAF dusts from a steelmaking company, without naming its location or defining their mineral phases. Table 4 reports 99.8% dry mass in both, with Zn 161000 and 390000 mg/kg dry mass in Dusts 1 and 2 respectively. Drying at 105 degrees C refers to dry-mass characterization; whole-feed sterilization or pretreatment is not stated. The named culture was grown in basal salts, elemental sulfur and 0.02 g/L yeast extract. Acid production used a 3-L working-volume stirred reactor at 30 degrees C, 160 rpm and 75 L/h air, with 20 g/L sulfur and 100 mL inoculum. After each two-week production cycle, fresh medium and sulfur replaced the contents and 100 mL from the previous culture reinoculated the next cycle. The authors call this fed-batch operation. Culture liquid passed through a 0.22-micrometre filter before duplicate 50-mL leaching assays. Assays varied 50-100 g/L dust, 30-50 degrees C and 2 minutes to 24 hours; leaching mixing speed is not given. The reactor's 160 rpm is not assigned to these separate leaching assays.
Curated Evidence Points:
Support
Source:
frueholz_2025
Results 3.1 and Table 5 report Dust 2 leachate Zn 29900 mg/L and Fe 3.0 mg/L after 10 minutes at 100 g/L and 30 degrees C. Against Table 4 feed concentrations, these correspond approximately to the abstract's 76.67% Zn and 0.02% Fe mobilization. Figure 6 shows a near-plateau for Dust 2 at this loading from 2 to 10 minutes; its error bars are standard deviations of duplicate assays. The reported 76.7 +/- 0.2% at 2 minutes is a separate time point, not the 10-minute uncertainty.
Partial
Source:
frueholz_2025
Dust 1 was less selectively leached in Table 5. Its 100-g/L leachate contains Zn 9745 and Fe 3710 mg/L, whereas Figure 6 depicts about 30% Zn extraction and Results 3.1 gives 28.9 +/- 0.2% at 2 minutes. The 10-minute table Zn concentration divided by the Table 4 Dust 1 inventory implies about 60.5%, not the figure's roughly 30%. These source representations are not silently reconciled or pooled. No corrected Dust 1 extraction percentage is established here.
Partial
Source:
frueholz_2025
The paper reports average culture-acid sulfate around 50 g/L and pH 0.3, describing its acidity as approximately 0.5 M. Acidity was calculated from pH and sulfate speciation, not directly titrated. The reported average does not provide assay-specific acid doses; Results 3.1 attributes between-series variation partly to initial instability of acid production. There is no matched reagent-sulfuric- acid comparison or uninoculated acid-production control in this experiment. Earlier chemical-acid studies cited in the paper support an alternative acid-dissolution explanation, not biological superiority.
Context_only
Source:
dsm504
The live collection record resolves DSM 504 to Acidithiobacillus thiooxidans. Species-level NCBI identity and catalogue identity do not establish stock purity, authentication, or a particular cellular dissolution pathway. The microbial contribution directly described here is production of the subsequently filtered lixiviant.
Bioanode-associated zinc depletion and cathodic deposition from leachate
recovery
Microbial
A mixed microbial anode supplied with simulated wastewater was coupled to a stainless-steel cathode receiving purified and diluted Dust 2 leachate. With an externally controlled anode potential, zinc largely disappeared from catholyte and a zinc-rich electrode deposit was analyzed. This supports a laboratory bioelectrochemical recovery stage, while separating solution depletion from deposit yield and overall dust-to-product recovery. The anode community was not taxonomically resolved in this experiment and is not assigned to A. thiooxidans.
Experimental Context & Analytical Limits:
Methods 2.5-2.6 used Dust 2 leachate, hydrogen peroxide described as 30 vol% without an unambiguous added-volume specification, and 2-M NaOH to raise pH from 2.9 to 3.8. After impurity precipitation, 0.22-micrometre filtration and a stated 1:1 dilution, Table 3 gives Zn 1785, Fe 56, Mn 21 and Cr 6 mg/L in the MEC feed. A two-chamber H-cell used a proton exchange membrane, 12.5-square-centimetre carbon-felt anode and 316-stainless-steel cathode, with 220 mL per chamber. The anode was inoculated with 110 mL mixed-culture anolyte from another MEC plus 110 mL nutrient medium. Following four weeks of acclimation, the cathode chamber received the prepared leachate. Room-temperature operation used 70 rpm stirring and seven-day catholyte exchanges. Simulated wastewater, reported COD 675 mg/L, was supplied twice weekly while half the anolyte was replaced and CO2 flushing maintained anaerobic conditions. A potentiostat held the anode at -100 mV versus Ag/AgCl in 3-M NaCl; this is not an applied cell voltage or a cathode potential. Each cycle's electrode deposit was dissolved in dilute HCl for ICP analysis and electrode regeneration.
Methods 2.5-2.6 used Dust 2 leachate, hydrogen peroxide described as 30 vol% without an unambiguous added-volume specification, and 2-M NaOH to raise pH from 2.9 to 3.8. After impurity precipitation, 0.22-micrometre filtration and a stated 1:1 dilution, Table 3 gives Zn 1785, Fe 56, Mn 21 and Cr 6 mg/L in the MEC feed. A two-chamber H-cell used a proton exchange membrane, 12.5-square-centimetre carbon-felt anode and 316-stainless-steel cathode, with 220 mL per chamber. The anode was inoculated with 110 mL mixed-culture anolyte from another MEC plus 110 mL nutrient medium. Following four weeks of acclimation, the cathode chamber received the prepared leachate. Room-temperature operation used 70 rpm stirring and seven-day catholyte exchanges. Simulated wastewater, reported COD 675 mg/L, was supplied twice weekly while half the anolyte was replaced and CO2 flushing maintained anaerobic conditions. A potentiostat held the anode at -100 mV versus Ag/AgCl in 3-M NaCl; this is not an applied cell voltage or a cathode potential. Each cycle's electrode deposit was dissolved in dilute HCl for ICP analysis and electrode regeneration.
Curated Evidence Points:
Support
Source:
frueholz_2025
Results 3.3 and Figure 8 report 99.7-100% Zn removal from catholyte, averaging 99.9 +/- 0.1% across seven serial batch cycles. Reported cathodic coulombic efficiency averaged 69.3 +/- 13.2%, COD removal 80.9 +/- 9.4%, and current density 2.3 +/- 0.4 A per square metre. These cycles share the operating MEC and are not seven independent reactors. The source's near-total recovery wording refers to the already prepared catholyte inventory, not the original dust inventory.
Context_only
Source:
spiess_2023_methods
The 2025 paper explicitly delegates its Zn recovery calculation to Equation 1 of this earlier study: the difference between initial and final catholyte Zn concentrations divided by the initial concentration. This is a solution-depletion metric. The earlier study's distinct blast-furnace feed, microbial community, electrode and performance values are not imported as observations on the 2025 EAF system.
Support
Source:
frueholz_2025
Figure 9 and Results 3.3 report mean analyzed deposit composition of 99.15% Zn, 0.48% Mn, 0.30% Fe and 0.08% Cr across seven cycles, with Zn rounded to 99.2% in the abstract. Deposited material was acid-dissolved and analyzed by ICP. These selected-metal proportions do not by themselves determine complete deposit mass, oxygen content, zinc oxidation state, phase purity or a certified marketable product.
Partial
Source:
frueholz_2025
The abstract reports 48% Fe precipitation, whereas Results 3.2 and Figure 7B give about 42%; the figure specifies n = 4. Results also report 24% Cr, 6% Mn and 2% Zn precipitation at pH 3.8. The Fe discrepancy is unresolved. The specific preliminary Dust 2 leachate batch entering purification is not identified sufficiently to connect Table 3 Zn 1785 mg/L after 1:1 dilution to the best Table 5 Zn 29900 mg/L result. Those concentrations must not be treated as a closed sequential mass balance or multiplied into an overall yield.
Partial
Source:
frueholz_2025
No matched abiotic-anode or open-circuit comparator, independent MEC replication, full deposit mass balance or measured process energy budget is reported. Catholyte depletion alone cannot exclude other zinc sinks. Comparisons with conventional electrowinning and lower energy consumption reported in other studies are contextual, not demonstrated advantages for this EAF experiment. Proposed reuse in galvanizing and reuse of iron-rich residue were not tested here. Industrial dust origin does not establish industrial biological operation, validated residue safety, or a deployable closed process.
Sources & References
-
frueholz_2025: Frueholz, Spiess, Eisbacher-Lubensky, Habermaier, Guebitz, Mueller and Haberbauer (2025). Zn recovery from steel mill EAF dusts: A two-step biotechnological approach. Resources, Conservation & Recycling Advances 27:200278. DOI 10.1016/j.rcradv.2025.200278; available online 16 July 2025, September issue. Full nine-page article, Methods 2.1-2.7, Results 3.1-3.3, Tables 1-5 and Figures 1-9 inspected.
https://doi.org/10.1016/j.rcradv.2025.200278 (accessed 2026-10-11) -
spiess_2023_methods: Spiess et al. (2023). Zinc recovery from bioleachate using a microbial electrolysis cell and comparison with selective precipitation. Frontiers in Microbiology 14:1238853. DOI 10.3389/fmicb.2023.1238853. Analytics and calculations, Equations 1-2, cited by the 2025 EAF study to define its recovery and coulombic-efficiency calculations. This earlier experiment used blast-furnace dust bioleachate, not the 2025 EAF feed.
https://doi.org/10.3389/fmicb.2023.1238853 (accessed 2026-10-11) -
dsm504: DSMZ culture catalogue, DSM 504, Acidithiobacillus thiooxidans. Confirms the accession-to-species mapping reported by the EAF study; it does not independently authenticate the experimental stock.
https://www.dsmz.de/collection/catalogue/details/culture/DSM-504 (accessed 2026-10-11) -
ncbi_thiooxidans: NCBI Taxonomy 930, Acidithiobacillus thiooxidans, species-level identity.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=930&mode=Info (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T15:29:57.478716+00:00 |
Codex (GPT-6; Codex) | CREATE | Curated actual EAF dust with separate filtered biogenic-acid leaching and microbial-electrolysis stages, preserving source conflicts, conditional denominators, unresolved mixed-culture identity and laboratory scope. |
Record source: data/records/electric-arc-furnace-dust.yaml