Spent sulfuric-acid-production catalyst secondary resource
Used catalyst from sulfur-dioxide oxidation in sulfuric-acid production, represented here by vanadium-bearing material from a copper-smelter acid unit. This process-defined secondary resource is distinct from petroleum hydrodesulfurization catalysts, automotive converters, fresh catalyst and its constituent elements or mineral phases. The selected silica-rich feed does not define every spent acid-plant catalyst. No constituent-element criticality designation is inherited.
Microbial & Biochemical Mechanisms (1)
Loading-dependent culture-associated vanadium mobilization
bioleaching
Microbial
Associated Organisms:
Acidithiobacillus thiooxidans (NCBITaxon:930)
Living Acidithiobacillus thiooxidans DSM 9463 culture with elemental sulfur was associated with increased filtered-liquid vanadium at low catalyst loading, together with acidification and increasing sulfate. Higher-loading experiments lacked the same advantage over uninoculated controls. The evidence supports a conditional laboratory solubilization observation, without establishing direct enzymatic vanadium reduction, isolated vanadium recovery or industrial deployment.
Experimental Context & Analytical Limits:
Mikoda et al. (2020) studied actual spent catalyst from a copper-smelter sulfuric-acid unit: approximately 10-mm granules were comminuted and sieved. Main Methods name 100- and 200-micrometre sieves, whereas supplementary Figure S1 names a 250-micrometre sieve; the fraction used for each bioleaching arm is not explicitly assigned. Table 3 reports 65.5 wt% SiO2 and 5.50 wt% V2O5 on an oxide-composition basis, not pure vanadium oxide or a universal feed composition. Culture DSM 9463 was supplied by DSMZ, pregrown in mineral medium with 1% w/v sulfur to reported pH 1.7, and added at 2% v/v. Assays used fresh mineral medium initially adjusted to pH 2.5 with sulfuric acid, 2% w/v added elemental sulfur, 28 degrees C and 100 rpm. Materials were autoclaved at 121 degrees C for 15 minutes. The paper names 50-cm3 flasks but does not clearly specify working liquid volume. Pulp densities were 1, 2, 5, 10 and 20%, with at least duplicate biotic and uninoculated batches sampled on days 1, 7, 14, 21 and 28. Pulp-density percentages are retained as source labels rather than silently assigned an unstated basis. Liquid aliquots were filtered at 0.22 micrometres, diluted and acidified for ICP-MS total-element V analysis; the stated quantification limit was 0.001 mg/L. No pH-trajectory-matched sterile acid control was reported.
Mikoda et al. (2020) studied actual spent catalyst from a copper-smelter sulfuric-acid unit: approximately 10-mm granules were comminuted and sieved. Main Methods name 100- and 200-micrometre sieves, whereas supplementary Figure S1 names a 250-micrometre sieve; the fraction used for each bioleaching arm is not explicitly assigned. Table 3 reports 65.5 wt% SiO2 and 5.50 wt% V2O5 on an oxide-composition basis, not pure vanadium oxide or a universal feed composition. Culture DSM 9463 was supplied by DSMZ, pregrown in mineral medium with 1% w/v sulfur to reported pH 1.7, and added at 2% v/v. Assays used fresh mineral medium initially adjusted to pH 2.5 with sulfuric acid, 2% w/v added elemental sulfur, 28 degrees C and 100 rpm. Materials were autoclaved at 121 degrees C for 15 minutes. The paper names 50-cm3 flasks but does not clearly specify working liquid volume. Pulp densities were 1, 2, 5, 10 and 20%, with at least duplicate biotic and uninoculated batches sampled on days 1, 7, 14, 21 and 28. Pulp-density percentages are retained as source labels rather than silently assigned an unstated basis. Liquid aliquots were filtered at 0.22 micrometres, diluted and acidified for ICP-MS total-element V analysis; the stated quantification limit was 0.001 mg/L. No pH-trajectory-matched sterile acid control was reported.
Curated Evidence Points:
Support
Source:
mikoda_2020
Results 3.2, Figure 7 and Perspectives 3.3 assign day-21 liquid V release of 93% to 1% pulp density and 85.5% to 2%, versus at most 17% in the corresponding uninoculated series. These source percentages normalize filtered-liquid V to the initial feed V inventory; they are not isolated product yields. Lower culture pH and increasing sulfate in Figure 9 support culture-associated acidification, without separating the effects of cells from their evolving solution chemistry.
Partial
Source:
mikoda_2020
The abstract instead attributes 93% to 2% pulp density. Results 3.2 also labels both day-28 values, 80% and 74%, as 1%, while Figure 7 distinguishes the two arms. These inconsistencies remain unresolved. The low-loading liquid V inventory declined after day 21. At 5-20% pulp density, Figure 8 shows decreasing liquid V with controls often exceeding inoculated arms; no universal microbial advantage or monotonic extraction is established. Oxygen-transfer limitation and precipitation are proposed explanations, not independently isolated causes.
Partial
Source:
mikoda_2020_supplement
Figures S2-S3 show a qualitative sulfur-settling transfer assay and changing solution color. These are activity/speciation clues, not cell counts, quantified survival, or direct measurement of V oxidation state. Figure S1's sieve description conflicts with main Methods. The observed colors cannot independently establish a microbial V(V)-reduction pathway.
Partial
Source:
mikoda_2020
Figures 1-2 and Table 3 describe mixed feed and residual phases; disappearance of XRD peaks and lower residual-solid V concentration do not supply residue mass or a complete V balance. Color and the pH/Eh comparison in Figure 6 do not directly identify dissolved V species. Kinetic fits use selected incomplete time series to improve R-squared values (Methods 2.5), so they do not demonstrate a unique rate-controlling mechanism. Separate reagent-grade citric-acid leaching is abiotic, under different temperature, duration and vessel conditions; it is not evidence that DSM 9463 produced citrate.
Context_only
Source:
mikoda_residues
This related same-group study explicitly follows the earlier work and repeats its raw/residue oxide compositions. Its 2%-pulp-density 93% claim does not resolve the earlier arm conflict or establish independent replication. The approximately 96% statement compares solid V concentrations, without residue-mass accounting for a recovered yield. The separate SPLP assay (1 g residue, 20 mL pH-4.2 solution, 18 hours) reports bioleached-residue V and Al of 6.4 and 4.8 mg/L in Table 3; residual leachability remains. These observations do not demonstrate a metal-free or universally safe residue, a regulatory determination, validated concrete use, or a recovered vanadium product.
Sources & References
-
mikoda_2020: Mikoda, Potysz, Kucha and Kmiecik (2020). Vanadium removal from spent sulfuric acid plant catalyst using citric acid and Acidithiobacillus thiooxidans. Archives of Civil and Mechanical Engineering 20:132. DOI 10.1007/s43452-020-00136-9; Methods 2.1-2.5, Results 3.1-3.3, Tables 1-3 and Figures 1-9.
https://doi.org/10.1007/s43452-020-00136-9 (accessed 2026-10-11) -
mikoda_2020_supplement: Supplementary material to Mikoda et al. (2020), DOI 10.1007/s43452-020-00136-9. Figures S1-S3: catalyst preparation, post-experiment activity test and culture-liquid color. DOCX inspected, including its embedded figure images.
https://media.springernature.com/original/springer-static/esm/art%3A10.1007%2Fs43452-020-00136-9/MediaObjects/43452_2020_136_MOESM1_ESM.docx (accessed 2026-10-11) -
mikoda_residues: Mikoda, Potysz, Gruszecka-Kosowska, Kmiecik and Tomczyk. Spent sulfuric acid plant catalyst: valuable resource of vanadium or risky residue? Process comparison for environmental implications. Published online 27 October 2020; Environmental Science and Pollution Research 28:59358-59367 (2021). DOI 10.1007/s11356-020-11349-z; Methods, Figures 1-3 and Tables 1-4.
https://doi.org/10.1007/s11356-020-11349-z (accessed 2026-10-11) -
dsm9463: DSMZ catalogue: Acidithiobacillus thiooxidans DSM 9463, strain designation B-S2, isolated from an Australian bioleaching reactor. Collection identity does not independently verify the study's experimental stock.
https://www.dsmz.de/collection/catalogue/details/culture/DSM-9463 (accessed 2026-10-11) -
ncbi_thiooxidans: NCBI Taxonomy 930: Acidithiobacillus thiooxidans, species. This identifier does not identify the experimental DSM 9463 stock.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=930&mode=Info (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T14:19:32.351097+00:00 |
Codex (GPT-6; Codex) | CREATE | Created the process-defined spent sulfuric-acid catalyst record from primary full text and supplements, retaining loading-dependent controls, source contradictions, companion-study overlap and laboratory recovery limits. |
Record source: data/records/spent-sulfuric-acid-production-catalyst.yaml