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Heavy-fuel-oil combustion ash secondary resource

Heterogeneous ash generated by burning heavy fuel oil, represented here by an oil-fired thermal-power-plant residue. This combustion resource is distinct from coal fly ash, petroleum coke, refinery catalysts and its constituent elements. The selected study does not establish the collection fraction needed to identify its sample specifically as fly ash. No constituent-element criticality status is inherited by this resource.

Microbial & Biochemical Mechanisms (1)

Reported metal extraction with Aspergillus niger spent medium

bioleaching Microbial

Associated Organisms: Aspergillus niger (NCBITaxon:5061)

Rasoulnia and Mousavi report vanadium and nickel extraction after contact of oil-fired ash with culture liquid from Aspergillus niger PTCC 5210 following biomass separation. Organic-acid measurements establish production of potential lixiviants, but the study does not isolate a unique causal metabolite or establish a microbial enhancement over matched abiotic leaching. This is a laboratory spent-medium observation, not evidence for fungal growth at the leaching temperature or industrial metal recovery.

Experimental Context & Analytical Limits:
The paper describes ash supplied by a thermal power plant in Tehran, Iran, ground and screened below 75 micrometres. Its exact plant name, collection location and fly-ash versus other residual fraction are not specified. The fungus is source-reported as PTCC 5210 purchased from IROST; its current collection entry was not independently resolved. Seven-day potato-dextrose-agar cultures supplied a spore suspension. The paper states 10^7 spores without an explicit volume denominator or final inoculum fraction. Culture medium contained, per litre, 100 g sucrose, 1.5 g NaNO3, 0.5 g KH2PO4, 0.025 g MgSO4.7H2O, 0.025 g KCl and 1.6 g yeast extract. Flask cultivation lasted fourteen days at 30 degrees C and 130 rpm. A bubble column with 1-L working culture volume operated for seven days at 30 degrees C and 760 mL/min aeration. Biomass separation is stated without a specified separation procedure or residual-cell assessment. Both spent media subsequently contacted ash at 3% w/v, 60 degrees C for seven days. Leaching-vessel volume and agitation are not specified; the 1-L value describes culture production. Organic acids were analyzed by HPLC and feed composition by XRF. Sterilized conditions are stated, but no matched sterile-medium, pure-acid or pH-controlled ash-leaching comparison is reported.
Curated Evidence Points:
Section III, page 367 and Figure 2 report extraction percentages of 97% V and 50% Ni with flask-derived spent medium, compared with 100% V and 33% Ni with bubble-column-derived medium. These are source-reported leaching outcomes, not independently reconstructed yields or isolated-product recovery. The text reports citric-acid-rich flask medium and oxalic-acid-rich reactor medium after the different culture durations. The lower Ni result remains explicit rather than treating reactor cultivation as uniformly superior.
The complete four-page paper does not specify the liquid-metal assay, sampling fraction, yield equation, replication count or uncertainty for Figure 2. Figure 1 has error bars for agar colony diameter but does not define them or provide an ash-leaching control. Culture duration, aeration and possibly inoculum differ, preventing attribution of the yield contrast solely to vessel scale or one organic acid. Without matched abiotic leaching or complete solution/residue balances, the quoted 100% must not be interpreted as demonstrated quantitative recovery of a purified vanadium product.
Nickel-oxalate precipitation is proposed to explain the lower Ni extraction, but Figure 3 labels NiO in the treated solid and does not independently identify a nickel-oxalate phase. The diffraction text emphasizes a sodium iron sulfate residue, while the treated trace additionally labels NaHSO4.H2O and NiO. Neither supports claiming a single-phase residue. Loss of assigned vanadium peaks cannot demonstrate complete vanadium removal below an unstated diffraction detection limit. Figure 4 shows selected surface changes, not quantitative porosity, phase-specific flux or safe residue reuse.
Section III reports aeration difficulties with longer bubble-column fermentation because of biomass accumulation. The 1-L culture system and subsequent spent-medium assay therefore demonstrate laboratory process comparison only. No isolated metal product, economic balance, continuous industrial operation or comprehensive toxicity assessment is established by this paper.

Sources & References

  1. rasoulnia_mousavi_2016: Rasoulnia and Mousavi (2016). Bioleaching of Precious Metals from an Oil-Fired Ash Using Organic Acids Produced by Aspergillus Niger in Shake Flasks and Bioreactor. International Journal of Chemical Engineering and Applications 7(6):365-368. DOI 10.18178/ijcea.2016.7.6.606; complete four-page publisher PDF, Sections II-IV and Figures 1-4.
    https://www.ijcea.org/vol7/606-G0007.pdf (accessed 2026-10-11)
  2. ncbi_niger: NCBI Taxonomy 5061, Aspergillus niger, species-level identity. This mapping does not independently authenticate the reported PTCC culture.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=5061&mode=Info (accessed 2026-10-11)

Curation History

Timestamp Curator Action Summary
2026-10-11T14:54:56.332589+00:00 Codex (GPT-6; Codex) CREATE Curated a distinct oil-combustion-ash resource and source-scoped fungal spent-medium observation, preserving analytical, control and scale limits.

Record source: data/records/heavy-fuel-oil-combustion-ash.yaml