Spent automotive three-way catalyst secondary resource
Used automotive three-way catalytic-converter material, represented here by a real vehicle-treatment-centre catalyst containing a ceramic support and metal-bearing coating. This use-defined secondary resource is distinct from its constituent platinum-group elements, fresh catalyst, refinery hydrocracking or hydrodesulfurization catalysts, and automotive wastewater-treatment sludge. The selected cryomilled feed does not define every converter formulation. No constituent criticality designation is inherited.
Microbial & Biochemical Mechanisms (1)
Biogenic-acid pretreatment of spent three-way catalyst
bioleaching
Microbial
Associated Organisms:
Acidithiobacillus thiooxidans (NCBITaxon:930)
Acidithiobacillus thiooxidans DSM 11478 cultures produced acidic media subsequently applied to pulverized spent automotive catalyst. Culture-containing and bacteria-depleted media mobilized aluminium, with a condition-dependent comparison against commercial sulfuric acid. The experiment demonstrates a laboratory pretreatment observation, not phase-specific alumina removal, validated platinum-group enrichment, isolated metal recovery or industrial deployment.
Experimental Context & Analytical Limits:
Compagnone et al. obtained a real spent three-way catalyst from the El Caimán authorized vehicle-treatment centre in Cádiz and cryomilled it. The main text reports XRF feed aluminium and platinum; complete composition is assigned to unavailable Table S1. Acid preparation used 180 mL 0K medium, 20 mL exponential-phase inoculum and 2 g biogenic sulfur, at 30 degrees C and 150 rpm. The sulfur came from a separate anoxic biogas-desulfurization process. Day-4 exponential and day-14 stationary cultures provided initially pH 1 and pH 0.7 lixiviants; sulfur-removal filtration retained cells. Day-20 culture was centrifuged at 1610 x g for 10 minutes to make the source-labelled bacteria-free pH 0.55 lixiviant; complete cell removal was not independently demonstrated. Commercial sulfuric acid at pH 0.55 was the chemical comparator. Each lixiviant treated 5, 30 or 60% w/v catalyst for 14 days at 30 degrees C and 150 rpm. These are unlike culture ages and starting chemistries, not matched-pH microbial-versus-sterile pairs. Samples were centrifuged at 1610 x g for 10 minutes, with recovered liquid analyzed by an aluminium photometric assay and endpoint ICP-AES. The paper does not clearly report independent replicate counts for the catalyst-leaching arms; triplication stated for the separate sulfur/pH experiment and local EDX measurements must not be transferred to these arms.
Compagnone et al. obtained a real spent three-way catalyst from the El Caimán authorized vehicle-treatment centre in Cádiz and cryomilled it. The main text reports XRF feed aluminium and platinum; complete composition is assigned to unavailable Table S1. Acid preparation used 180 mL 0K medium, 20 mL exponential-phase inoculum and 2 g biogenic sulfur, at 30 degrees C and 150 rpm. The sulfur came from a separate anoxic biogas-desulfurization process. Day-4 exponential and day-14 stationary cultures provided initially pH 1 and pH 0.7 lixiviants; sulfur-removal filtration retained cells. Day-20 culture was centrifuged at 1610 x g for 10 minutes to make the source-labelled bacteria-free pH 0.55 lixiviant; complete cell removal was not independently demonstrated. Commercial sulfuric acid at pH 0.55 was the chemical comparator. Each lixiviant treated 5, 30 or 60% w/v catalyst for 14 days at 30 degrees C and 150 rpm. These are unlike culture ages and starting chemistries, not matched-pH microbial-versus-sterile pairs. Samples were centrifuged at 1610 x g for 10 minutes, with recovered liquid analyzed by an aluminium photometric assay and endpoint ICP-AES. The paper does not clearly report independent replicate counts for the catalyst-leaching arms; triplication stated for the separate sulfur/pH experiment and local EDX measurements must not be transferred to these arms.
Curated Evidence Points:
Support
Source:
compagnone_2023
Methods 2.1-2.5 and Figure 4 identify the feed and leaching comparison. At 5% w/v catalyst, the day-14 stationary-culture acid gave higher reported liquid aluminium release than the bacteria-depleted, exponential-culture and commercial-acid arms. Figure 4 gives 54.5%, 23.4%, 21.7% and 24.7%, respectively, on the source's feed-normalized aluminium-leaching basis. These are reported leaching percentages, not isolated-product recovery. The lower-loading advantage does not establish a universal advantage of living cells or a specific gene or enzyme mechanism.
Partial
Source:
compagnone_2023
Figure 4 is narrower than Results 3.4 prose. At 30% w/v, the plotted bacteria-free value of 5.9% exceeds the stationary-culture value of 5.1%; at 60% w/v, the plotted stationary-culture 2.5% slightly exceeds bacteria-free 2.4%. The text instead calls bacteria-free acid highest at both high loadings and quotes 5.9% collectively. No significance assessment establishes that the 60% difference is meaningful. The economic discussion separately uses 57.1% aluminium extraction where the abstract, main result and Figure 4 use 54.5%. These discrepancies remain unresolved; neither high-loading superiority nor a reconciled optimum is asserted.
Partial
Source:
compagnone_2023
Total-element aluminium in the recovered liquid cannot assign dissolution uniquely to the alumina coating instead of the aluminium-bearing ceramic support. Initial sulfuric-acid concentration was estimated rather than measured, and the differing ages, residual chemistry and pH trajectories limit attribution to live cells. The main text's cell-count trends and microscopy suggest activity and association, but they do not demonstrate sulfur-residue consumption, an EPS-specific causal pathway or necessity of direct cell contact.
Partial
Source:
compagnone_2023
Results 3.4 calculates platinum-group enrichment from assumed retained platinum and aluminium mass loss; it does not measure a recovered PGM product. That section reports non-detection of Pt in post-treatment liquid and solid analyses, without a detection limit, while Results 3.5 reports Pt in selected EDX-analyzed biological globules. Figures 5-6 show selected surfaces and aggregates, not a bulk mass balance or proof of intracellular uptake. Local EDX composition is not a percentage of feed platinum recovered. Source percentage bases also switch between w/w and w/v in discussing feed composition. Unknown analytical detection limits, unresolved heterogeneous fractions and unavailable supplementary composition prevent stronger recovery or purity claims.
Sources & References
-
compagnone_2023: Compagnone, González-Cortés, Yeste, Cantero and Ramírez (2023). Bioleaching of the α-alumina layer of spent three-way catalysts as a pretreatment for the recovery of platinum group metals. Journal of Environmental Management 345:118825. DOI 10.1016/j.jenvman.2023.118825; Methods 2.1-2.6, Results 3.2-3.5, Figures 2-6. Full primary repository PDF inspected; supplementary files and underlying dataset contents unavailable in this assessment.
https://doi.org/10.1016/j.jenvman.2023.118825 (accessed 2026-10-11) -
dsm11478: DSMZ catalogue: Acidithiobacillus thiooxidans DSM 11478, strain designation Tth04. Confirms collection strain identity; does not independently verify the experimental stock.
https://www.dsmz.de/collection/catalogue/details/culture/DSM-11478 (accessed 2026-10-11) -
ncbi_thiooxidans: NCBI Taxonomy 930: Acidithiobacillus thiooxidans, species. The species identifier is distinct from DSM 11478 strain provenance.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=930&mode=Info (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T13:46:54.274021+00:00 |
Codex (GPT-6; Codex; round23_identity_gaps) | CREATE | Created a distinct spent automotive three-way-catalyst resource from rechecked primary evidence and authority-verified organism identity; retained acid-comparator, figure/text, phase-assignment and platinum-recovery limits. |
Record source: data/records/spent-automotive-three-way-catalyst.yaml