Phosphate-ore tailings secondary resource
Residual material from phosphate-ore processing, distinct from phosphate rock as a commodity, a phosphate concentrate, phosphogypsum and a pure phosphate mineral. The curated example is the Florida phosphate tailings specimen studied by Somasundaran and colleagues, described as predominantly clay-bearing and supplied by Florida University, USA. The paper does not identify its mine or processing plant. Composition and leaching behavior are specimen-specific; constituent rare earth elements do not confer a criticality designation on this resource.
Microbial & Biochemical Mechanisms (1)
Culture-associated rare earth leaching in bacterial and fungal arms
bioleaching
Microbial
Associated Organisms:
Acidithiobacillus ferrooxidans (NCBITaxon:920), Aspergillus niger (NCBITaxon:5061)
Separate living cultures identified as Acidithiobacillus ferrooxidans and Aspergillus niger were incubated with phosphate tailings in laboratory shake flasks. The paper reports aggregate rare earth signal in clarified leachate. Without matched sterile or acid-matched leaching controls, these observations establish culture-associated leaching but not a microbial increment, an exclusive biochemical pathway or recovery of an isolated rare earth product.
Experimental Context & Analytical Limits:
Methods p.55 describe 500 mL flasks with 250 mL medium, 1% pulp density, 30 degrees C and 150 rpm. The bacterial arm used ferrous sulfate 9K medium adjusted to leaching pH 1.7, distinct from growth medium pH 2.5, and 1 mL stationary-phase inoculum reported as approximately 5 x 10^8 cells/mL. Its ATCC accession is unspecified. The fungus was isolated from phosphate concentrate and ore-adapted; it used modified Czapek-Dox liquid medium, with pH 7.5 in Figure 4. Methods report autoclaving fungal samples and medium at 121 degrees C, but conflict between one mL culture and two mL spore inoculum. The received tailings particle size was about 147 micrometres; Figures 3-4 explicitly specify ground 75 micrometre particles for both accepted time-series arms. Later optimization compares several separately ground size classes. The nominal 2-3 day bacterial and 24 h fungal methods conflict with time-series figures extending to six and five days, respectively. Figures 1-2 show pure-culture growth curves, without explicit paired with-feed and without-feed series. They are not uninoculated leaching controls. Leachate was filtered through Whatman No.1 paper and centrifuged at 7000 rpm for more than ten minutes before an Arsenazo I colorimetric assay near 520 nm. This is an operational aggregate assay, not an element-resolved analysis. The paper does not supply sufficient calibration, interference or mass-balance information to independently validate its absolute extraction percentages. These are laboratory observations, not evidence of industrial deployment or environmental or economic superiority.
Methods p.55 describe 500 mL flasks with 250 mL medium, 1% pulp density, 30 degrees C and 150 rpm. The bacterial arm used ferrous sulfate 9K medium adjusted to leaching pH 1.7, distinct from growth medium pH 2.5, and 1 mL stationary-phase inoculum reported as approximately 5 x 10^8 cells/mL. Its ATCC accession is unspecified. The fungus was isolated from phosphate concentrate and ore-adapted; it used modified Czapek-Dox liquid medium, with pH 7.5 in Figure 4. Methods report autoclaving fungal samples and medium at 121 degrees C, but conflict between one mL culture and two mL spore inoculum. The received tailings particle size was about 147 micrometres; Figures 3-4 explicitly specify ground 75 micrometre particles for both accepted time-series arms. Later optimization compares several separately ground size classes. The nominal 2-3 day bacterial and 24 h fungal methods conflict with time-series figures extending to six and five days, respectively. Figures 1-2 show pure-culture growth curves, without explicit paired with-feed and without-feed series. They are not uninoculated leaching controls. Leachate was filtered through Whatman No.1 paper and centrifuged at 7000 rpm for more than ten minutes before an Arsenazo I colorimetric assay near 520 nm. This is an operational aggregate assay, not an element-resolved analysis. The paper does not supply sufficient calibration, interference or mass-balance information to independently validate its absolute extraction percentages. These are laboratory observations, not evidence of industrial deployment or environmental or economic superiority.
Curated Evidence Points:
Support
Source:
somasundaran2018
Methods pp.54-55 and Figures 3-4 support the narrow observation that the authors tested the two named cultures separately on Florida phosphate tailings and reported rare earth signal in clarified liquid. The species labels are the authors' assignments; neither a strain accession nor sequence-based identification is supplied for the experimental organisms.
Partial
Source:
somasundaran2018
Figure 3 and the accompanying text report approximately 45% leached from tailings by day three in the bacterial arm, whereas Figure 4 and text report approximately 22.5% in the fungal arm. These are source-reported assay-based fractions, not independently validated yields or isolated-product recovery. The corresponding concentrate results, 70% and 42.5%, do not belong to tailings. Different media and pH and the absence of matched sterile leaching arms prevent interpreting the comparison as intrinsic species efficiency or proof of microbial necessity. Figure 3's caption identifies duplicate experiments; this does not establish the replication of every other experimental series.
Partial
Source:
somasundaran2018
Table 1 prints total tailings REE content as 304 ppm, while its listed elemental cells sum to 305 ppm; the concentrate cells sum to 889 ppm versus a printed total of 826 ppm. No corrected total is inferred. Separate particle-size and pulp-density experiments report tailings maxima of 48% and 38%, but Figure 8 labels pulp density mg/50 mL while methods and prose use g/50 mL. Together with inconsistent timing and inoculum wording, these discrepancies prevent adopting a single verified optimized recipe. The record preserves the reported time-series observations with these limits.
Context_only
Source:
somasundaran2018
Equations and discussion propose iron oxidation, ferric hydrolysis and fungal organic-acid complexation. They do not directly measure the relevant metabolites or isolate their causal contributions in these tailings experiments. Discussion p.60 also refers to monazite isolates ML3-1 and WE3-F in wording not reconciled with this study's stated methods; those strains, feed and concentrations are not attributed to the Florida tailings experiment.
Sources & References
-
somasundaran2018: Somasundaran P, Hussien S, Patra P and El Shall H (2018). Environmentally Benign Bio-Leaching Extraction of Rare Earth Elements from Non-Conventional Resources. Annals of Microbiology and Research 2(1):54-60. DOI 10.36959/958/570. Complete seven-page publisher PDF inspected, including methods pp.54-55, Table 1 and Figures 1-8. Tailings and concentrate results are separate experimental feeds.
https://scholars.direct/Articles/microbiology/amr-2-009.pdf (accessed 2026-10-16) -
ncbi_ferrooxidans: NCBI Taxonomy, taxon 920, Acidithiobacillus ferrooxidans, rank species. This identifier does not resolve the study's unspecified ATCC strain.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=920&mode=info (accessed 2026-10-16) -
ncbi_niger: NCBI Taxonomy, taxon 5061, Aspergillus niger, rank species. This is the authors' species identification, not a verified strain or genome accession for their phosphate-concentrate isolate.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=5061&mode=info (accessed 2026-10-16)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-16T04:26:58.190965Z |
codex (GPT-6; codex) | CREATE | Added process-defined phosphate tailings and qualified culture-associated leaching evidence with controls, assay and source-consistency limits. |
2026-10-16T04:35:42.936385Z |
codex (GPT-6; codex) | EDIT | Corrected the time-series particle size to 75 micrometres and the pure-culture growth-figure scope after independent review issue464. |
Record source: data/records/phosphate-ore-tailings.yaml