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PGM Spent Catalyst Bioleaching Consortium

Community ID CommunityMech:000049
Ecological State ENGINEERED
Environment contaminated soil
ENVO:00002116 · HabitatMech ↗

An acidophilic bioleaching system for recovery of platinum group metals (PGMs) from spent automotive catalysts and hydroprocessing catalysts. Acidithiobacillus thiooxidans is the only organism the cited sources name: it generates sulfuric acid that dissolves the alumina support. The thiosulfate used for PGM complexation was sourced separately, from a biogas biodesulfurization bioreactor whose community the source does not characterise taxonomically. Spent three-way catalysts (TWC) from automotive exhaust systems contain precious metals (Pt, Pd, Rh) deposited on alumina (Al₂O₃) supports, while spent petroleum refinery hydroprocessing catalysts contain Pd, Ni, Mo, and Al. The consortium operates under acidic conditions in column bioreactors, achieving exceptional recovery rates: 93.2% Pd extraction, 82.9% Ni, 33.4% Al, and 22.7% Mo from spent petroleum catalysts. The bioleaching mechanism proceeds in two stages: (1) At. thiooxidans generates sulfuric acid that dissolves the alumina support matrix, exposing embedded PGM particles, and (2) biogenic thiosulfate (S₂O₃²⁻) produced during sulfur oxidation forms stable complexes with Pd and other PGMs in the presence of copper and ammonia, mobilizing them from the catalyst surface. The thiosulfate-copper-ammonia system enables selective PGM leaching without harsh cyanide reagents. This biotechnological approach offers an environmentally sustainable alternative to conventional pyrometallurgical PGM recovery (high-temperature smelting) and aggressive chemical leaching (aqua regia, cyanide), while addressing circular economy needs for critical materials recovery from automotive and industrial waste streams. The technology represents a significant advance in green metallurgy for spent catalyst recycling.

Taxonomy

Taxon Ontology ID Functional Roles Abundance
Acidithiobacillus thiooxidans NCBITaxon:930 · TaxonMech · TraitMech
PRIMARY_DEGRADER PRIMARY_PRODUCER
DOMINANT
  • doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO)
    "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"
  • doi:10.1016/j.jenvman.2019.04.081 - PARTIAL (IN_VITRO)
    "about 82.9% of Ni, 33.4% of Al, and 22.7% of Mo were leached after 315 h of column operation"
  • PMID:38138568 - SUPPORT (IN_VITRO)
    "A remarkable 96.2 and 93.2% of the total Pd was successfully extracted from the solid at 5% pulp density using both commercially available and biogenic thiosulfate, highlighting the method's versatility for Pd bioleaching from both thiosulfate sources."
  • PMID:31059950 - SUPPORT (IN_VITRO)
    "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"

Ecological Interactions

The graph shows only explicitly linked interaction participants. Community members without an asserted participant link are omitted; membership alone does not imply an interaction.

Ecological interaction network for PGM Spent Catalyst Bioleaching Consortium Bipartite graph where circles represent taxa and non-circular symbols represent interactions. Rare or untyped interactions share the Other symbol; exact curated types remain in the interaction details.
Taxon
Other

Aluminium Leaching from Refinery Catalyst

A. thiooxidans column bioleaching of an uncrushed refinery hydroprocessing catalyst released 33.4% of its Al after 315 h in submerged continuous operation. The accessible abstract reports a chemical-control kinetic fit for Al dissolution, not direct demonstration of gamma-alumina removal exposing PGM particles. This experiment is separate from synthetic Pd/alpha-alumina thiosulfate leaching; additional sulfur-oxidizing partners are not established.

Source Taxon: Acidithiobacillus thiooxidans

Metabolites: aluminium (CHEBI:28984 · MediaIngredientMech · CMMMech)

Evidence

  • PMID:31059950 - SUPPORT (IN_VITRO)
    "about 82.9% of Ni, 33.4% of Al, and 22.7% of Mo were leached"

Biogenic Thiosulfate Leaching of Synthetic Palladium Catalyst

A separate activated-sludge gas-lift system produced up to 4.9 g/L thiosulfate at pH 10. Its liquid was concentrated at 100 C and filtered before chemical leaching of synthetic metallic Pd on alpha-alumina at 60 C, pH 8 and 5% pulp. Biogenic thiosulfate removed 93.22% of Pd from the solid, but dissolved-phase recovery was 63.53%; precipitation accounts for the discrepancy. This is not A. thiooxidans thiosulfate production, a spent-refinery PGM column, demonstrated Pt/Rh recovery, a measured unique Pd-complex stoichiometry or proof of benign industrial operation.

Metabolites: thiosulfate (CHEBI:16094 · MediaIngredientMech · CMMMech), palladium (CHEBI:33363 · MediaIngredientMech · CMMMech), copper(2+) (CHEBI:29036 · MediaIngredientMech · CMMMech), ammonia (CHEBI:16134 · MediaIngredientMech · CMMMech)

Evidence

  • PMID:38138568 - SUPPORT (IN_VITRO)
    "with the Pd supported on alpha-alumina."
  • PMID:38138568 - SUPPORT (IN_VITRO)
    "93.22 ± 0.06% when employing biogenic thiosulfate."
  • PMID:38138568 - SUPPORT (IN_VITRO)
    "achieved a recovery rate in the liquid phase of 63.53 ± 0.07%"

Column Bioleaching of Refinery Catalyst Metals

Submerged continuous A. thiooxidans column operation on uncrushed spent hydroprocessing catalyst leached 82.9% Ni, 33.4% Al and 22.7% Mo after 315 h. V reached 53.6% at 105 h and then declined, consistent with precipitation; FESEM detected V in precipitates. The accessible abstract reports diffusion control for Ni and chemical control for Al/V/Mo. These are positive metal-extraction findings, not Pd/Pt/Rh recovery or a combined acid/thiosulfate cascade. Full-text conditions and mechanistic controls remain uninspected.

Source Taxon: Acidithiobacillus thiooxidans

Evidence

  • PMID:31059950 - SUPPORT (IN_VITRO)
    "from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans"
  • PMID:31059950 - SUPPORT (IN_VITRO)
    "The maximum yield of V (53.6%) in this column was achieved in 105 h"

Knowledge gaps & discussions (1)

KNOWLEDGE_GAP OPEN Which causal leaching steps are supported within each catalyst system separately?

The removed arrows joined distinct studies and matrices. PMID31059950 and DOI10.1016/j.jenvman.2019.04.081 are the same column article, not independent corroboration. Its abstract supports metal yields, not PGM exposure; full text remains inaccessible after publisher 403. The complete thiosulfate paper distinguishes synthetic alpha-alumina, filtered/concentrated lixiviant and solid versus liquid Pd. No coexisting supporting taxa or exact complex speciation should be invented.

Attaches to: ecological_interactions#Aluminium Leaching from Refinery Catalyst, ecological_interactions#Biogenic Thiosulfate Leaching of Synthetic Palladium Catalyst, ecological_interactions#Column Bioleaching of Refinery Catalyst Metals

1 evidence item(s)
IN_VITRO SUPPORT PMID:38138568

achieved a recovery rate in the liquid phase of 63.53 ± 0.07%

Separately quantifies dissolved Pd, preserving the precipitation limitation.

Environmental Factors

Factor Value Unit
pH for Alumina Dissolution 1.5-3.0 pH
  • PMID:38138568 - SUPPORT (IN_VITRO)
    "Based on these results, an optimization through an experimental design was performed, indicating the optimal conditions to be Na2S2O3 1.2 M, CuSO4 0.03 M, (NH4)2SO4 1.5 M, Na2SO3 0.2 M, pH 8, and 60 °C"
  • doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO)
    "Different operational strategies such as submerged bioleaching in continuous mode, submerged bioleaching in resting period mode, free flow bioleaching in continuous mode, and free flow bioleaching in resting period mode were tested to find out the optimum bioleaching strategy for the recovery of metals from spent hydroprocessing catalyst"
Column Bioreactor Configuration Continuous percolation qualitative
  • doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO)
    "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"
  • PMID:38138568 - SUPPORT (IN_VITRO)
    "Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"
Temperature 25-35 °C
  • doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO)
    "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"
  • PMID:38138568 - SUPPORT (IN_VITRO)
    "To optimize Pd bioleaching from a ground TWC, screening through a Plackett-Burman design determined that oxygen and temperature significantly affected the leaching yield negatively and positively, respectively"
PGM Recovery Efficiency 93.2% Pd, 82.9% Ni, 22.7% Mo % extraction
  • doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO)
    "Different operational strategies such as submerged bioleaching in continuous mode, submerged bioleaching in resting period mode, free flow bioleaching in continuous mode, and free flow bioleaching in resting period mode were tested to find out the optimum bioleaching strategy for the recovery of metals from spent hydroprocessing catalyst"
  • PMID:38138568 - SUPPORT (IN_VITRO)
    "Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"
Thiosulfate-Copper-Ammonia System S₂O₃²⁻ + Cu²⁺/Cu⁺ + NH₃/NH₄⁺ qualitative
  • PMID:31059950 - SUPPORT (IN_VITRO)
    "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"
  • PMID:38138568 - SUPPORT (IN_VITRO)
    "Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"
Substrate Type Spent TWC and hydroprocessing catalysts qualitative
  • doi:10.1016/j.jenvman.2019.04.081 - SUPPORT (IN_VITRO)
    "The feasibility of column bioleaching in the recovery of valuable metals (Ni, V, Mo, and Al) from an uncrushed petroleum refinery spent hydroprocessing catalyst using Acidithiobacillus thiooxidans has been reported"
  • PMID:38138568 - SUPPORT (IN_VITRO)
    "Bioleaching of palladium (Pd) using the thiosulfate-copper-ammonia leaching processes, with biogenic thiosulfate sourced from a bioreactor used for biogas biodesulfurization, is proposed as a sustainable alternative to conventional methods"

Growth Media

biogenic thiosulfate production medium (biogas biodesulfurization consortium)

Atmosphere MICROAEROBIC

Preparation notes: Thiosulfate-producing sulfur-oxidizing consortium operated under anoxic and microaerobic conditions; optimum biogenic thiosulfate (4.9 g/L) at batch mode, pH 10 and airflow 0.033 vvm.

Evidence

PMID:38138568

"Biogenic thiosulfate production was optimized in a gas-lift bioreactor by studying the pH (8-10) and operation modes (batch and continuous) under anoxic and microaerobic conditions for 35 d."

Cross-Mech Suite Links

Explore related entities across the CultureBotAI X-Mech knowledge bases:

HabitatMech: contaminated soil ↗ TaxonMech: Acidithiobacillus thiooxidans ↗ TraitMech: Acidithiobacillus thiooxidans ↗ CMMMech (Critical Minerals & REE) ↗ CultureMech Growth Media ↗ PathwayMech Pathways ↗