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PGM Spent Catalyst Bioleaching Consortium

Ecological State ENGINEERED
Environment contaminated soil
ENVO:00002874
Source File PGM_Spent_Catalyst_Bioleaching.yaml

An engineered acidophilic microbial consortium designed for sustainable recovery of platinum group metals (PGMs) from spent automotive catalysts and hydroprocessing catalysts. This bioleaching system employs a two-stage mechanism combining Acidithiobacillus thiooxidans for alumina support dissolution with biogenic thiosulfate producers for PGM complexation and mobilization. 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
PRIMARY_DEGRADER PRIMARY_PRODUCER
DOMINANT
Acidithiobacillus ferrooxidans NCBITaxon:920
PRIMARY_DEGRADER SYNTROPHIC_PARTNER
ABUNDANT
Sulfobacillus thermosulfidooxidans NCBITaxon:28034
PRIMARY_DEGRADER SYNTROPHIC_PARTNER
COMMON
Thiobacillus thioparus NCBITaxon:931
PRIMARY_PRODUCER
COMMON

Ecological Interactions

Alumina Support Matrix Dissolution

MUTUALISM

Source Taxon: Acidithiobacillus thiooxidans

Metabolites: sulfur (CHEBI:26833), sulfuric acid (CHEBI:26836), aluminium(3+) (CHEBI:28984), aluminium oxide (CHEBI:30073)

Biological Processes:

Downstream Effects:
→ Biogenic Thiosulfate-PGM Complexation

Evidence

  • 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"
  • 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"

Biogenic Thiosulfate-PGM Complexation

COMMENSALISM

Source Taxon: Acidithiobacillus thiooxidans

Metabolites: thiosulfate (CHEBI:16094), palladium (CHEBI:26156), copper(2+) (CHEBI:29036), ammonia (CHEBI:16134), platinum atom (CHEBI:33364), rhodium atom (CHEBI:33359)

Biological Processes:

Evidence

  • 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: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"

Column Bioreactor PGM Recovery

MUTUALISM

Metabolites: palladium (CHEBI:26156), nickel(2+) (CHEBI:49786), molybdenum atom (CHEBI:28685), platinum atom (CHEBI:33364), rhodium atom (CHEBI:33359)

Biological Processes:

Evidence

  • 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"

Thiosulfate Metabolic Cycling

SYNTROPHY

Source Taxon: Acidithiobacillus thiooxidans

Metabolites: thiosulfate (CHEBI:16094), sulfate (CHEBI:16189), sulfur (CHEBI:26833)

Biological Processes:

Evidence

  • PMID:31059950 - SUPPORT (IN_VITRO)
    "The bacterial attachment study with FESEM indicated that the metal toxicity was induced on bacterial cells attached to the sulfur particles"
  • 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"

Environmental Factors

Factor Value Unit
pH for Alumina Dissolution 1.5-3.0 pH
Column Bioreactor Configuration Continuous percolation qualitative
Temperature 25-35 °C
PGM Recovery Efficiency 93.2% Pd, 82.9% Ni, 22.7% Mo % extraction
Thiosulfate-Copper-Ammonia System S₂O₃²⁻ + Cu²⁺/Cu⁺ + NH₃/NH₄⁺ qualitative
Substrate Type Spent TWC and hydroprocessing catalysts qualitative