CMMMech
CMMMech > Secondary resource > Coal fly ash

Coal fly ash secondary resource

Fine particulate residue from coal combustion carried with flue gas and collected as fly ash, distinct from coal, coal bottom ash, municipal-waste incineration ash and sewage-sludge incineration ash. It is a heterogeneous secondary resource rather than a mineral species or a rare-earth commodity. A selected power-plant sample underwent laboratory treatment with yeast culture supernatant; constituent-element criticality is not inherited by the ash.

Microbial & Biochemical Mechanisms (1)

Element loss from coal fly ash after yeast-supernatant treatment

bioleaching Microbial

Associated Organisms: Starmerella bombicola (NCBITaxon:75736)

Park and Liang report decreased residual-solid element inventories following contact with supernatant from Candida (Starmerella) bombicola ATCC 22214. The study estimates extraction from the difference between initial and residual ash analyses, not by measuring recovered metal in solution. This supports a qualified laboratory leaching observation without identifying the active metabolite or a purified product.

Experimental Context & Analytical Limits:
Fly ash from Southern Illinois University Carbondale power plant was ball-milled for one hour and sieved to below 74 micrometres. The yeast was cultivated in glucose 100 g/L, yeast extract 10 g/L and urea 1 g/L medium, initially pH 5.5. A 10% v/v inoculum was grown with 1% w/v fly ash for three days at 28 degrees C, in darkness, 150 rpm. Centrifugation at 4500 x g for 15 minutes supplied supernatant for fresh-fly-ash contact at 28 degrees C, 50 rpm for six hours; Table 2 gives 1% pulp density for this leaching stage. Final solids were separated with a 0.45-micrometre membrane, water-washed, dried and heated at 550 degrees C for six hours. Initial/residual solids underwent dilute nitric/hydrochloric acid reflux at 95 degrees C for 30 minutes, then ICP-MS. Experiments were triplicated; leach volume is not specified. Water and fresh growth-media comparators were stated.
Curated Evidence Points:
Sections 2.3-2.4 and 3, Figure 3 report residual-inventory-based losses of 67.7% Yb, 64.6% Er, 63.0% Sc, 62.2% Y and 79.5% Mo for the ATCC 22214 supernatant. The approximately 59.7% mineral loss is a separate gravimetric denominator based on initial nonvolatile mineral residue, not a total-REE recovery yield. Figure 7 shows that extending culture production from three to six or nine days did not produce a reported significant increase in this mineral-loss measure.
The paper intentionally analyzes initial and residual solids rather than leaching liquor. Equal digestion procedures do not establish quantitative dissolution of all original and altered host phases, and no solution/residue mass balance or isolated product is supplied. The main figures do not report quantitative leaching outcomes for the stated water/fresh-medium controls; Figure 6 controls concern yeast growth without ash, not an acidity-matched sterile leach. Centrifugation is stated without sterile filtration of the spent medium. These limits prevent assigning the whole residual-inventory difference to microbial metabolism or claiming a universal dissolved-metal yield.
Organic-acid or sophorolipid causality is proposed but the active leaching chemicals were not isolated or measured in this experiment. Figure 2 labels the two nonselected comparator organisms in the opposite order to the corresponding mineral-loss values in running text, and Figure 3 gives Ce 27.3% while text groups the lowest light-REE losses as 28.1-30.7%. Those inconsistent details are not silently corrected or adopted. Results from the three organisms are not independent confirmation of a single molecular mechanism, and no commercial operation was tested.

Sources & References

  1. park_liang_2019: Park and Liang (2019). Bioleaching of trace elements and rare earth elements from coal fly ash. International Journal of Coal Science & Technology 6:74-83. DOI 10.1007/s40789-019-0238-5; Sections 2.1-2.4 and 3, Tables 1-2, Figures 1-3 and 6-7.
    https://doi.org/10.1007/s40789-019-0238-5 (accessed 2026-10-11)
  2. ncbi_starmerella: NCBI Taxonomy 75736: Starmerella bombicola, species; Candida bombicola is a listed synonym and ATCC 22214 is listed among type-material cultures.
    https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=75736 (accessed 2026-10-11)

Curation History

Timestamp Curator Action Summary
2026-10-11T09:26:04.464015+00:00 Codex (GPT-6; Codex) CREATE Created the distinct secondary-resource identity and source-scoped laboratory evidence, preserving control, measurement, scale and source-consistency limitations.

Record source: data/records/coal-fly-ash.yaml