Ion-adsorption rare-earth clay primary resource
Naturally weathered, rare-earth-bearing clay material, distinct from an individual clay mineral, isolated rare-earth element or processing residue. Separate curated experiments concern ferruginous, poorly sorted material from 3.8–4.8 m depth above volcanic breccia in the Ambohimirahavavy Alkaline Complex, Madagascar, and a Guangxi, China ore described as an ion-adsorption feed. Their specimens, communities, preparations and assays remain distinct; neither characterizes every ion-adsorption deposit.
Microbial & Biochemical Mechanisms (2)
Heterotrophic culture-associated rare-earth mobilization
bioleaching
Microbial
Associated Organisms:
Aspergillus (NCBITaxon:5052), Bacillus (NCBITaxon:1386)
Separate Aspergillus TD25 and Bacillus TD29 inoculations were associated with acidification and gradual rare-earth release from a nonsterile clay feed. Organic-acid measurements support an acid-associated interpretation, without isolating proton attack from ligand complexation or endogenous community effects. Salt leaching was generally faster and more effective; cerium showed the opposite comparison. Dissolved release is not an isolated rare-earth product or demonstrated industrial recovery.
Experimental Context & Analytical Limits:
Barnett et al. used living isolates from a separate country-rock profile; nonaseptic collection/storage limits claims of indigenous provenance. The reported genus assignments are retained: Table 3's closest GenBank matches do not identify the experimental isolates themselves. Triplicate treatments contained 3 g crushed/sieved feed below 0.5 mm and 150 mL liquid (2% w/v), incubated at 25 °C and 150 rpm for 60 days after 48 h inoculum cultivation. Modified phosphate-free CAB contained 140 g/L glucose; comparators were uninoculated CAB and 0.5 M ammonium sulfate. The feed was deliberately not sterilized. Late acidification in uninoculated flasks prevents treating them as abiotic controls. Leachate ICP-MS data were corrected for sampling and evaporation. No isolated-product recovery yield was reported.
Barnett et al. used living isolates from a separate country-rock profile; nonaseptic collection/storage limits claims of indigenous provenance. The reported genus assignments are retained: Table 3's closest GenBank matches do not identify the experimental isolates themselves. Triplicate treatments contained 3 g crushed/sieved feed below 0.5 mm and 150 mL liquid (2% w/v), incubated at 25 °C and 150 rpm for 60 days after 48 h inoculum cultivation. Modified phosphate-free CAB contained 140 g/L glucose; comparators were uninoculated CAB and 0.5 M ammonium sulfate. The feed was deliberately not sterilized. Late acidification in uninoculated flasks prevents treating them as abiotic controls. Leachate ICP-MS data were corrected for sampling and evaporation. No isolated-product recovery yield was reported.
Curated Evidence Points:
Support
Source:
barnett2018
Sections 2–3, Figures 1–3 and Tables 1–5 establish the feed, separate inoculations, measured acidification, organic ligands and solution release. At day 60, reported Lu release was 70.7% with Aspergillus versus 73.1% with salt, relative to total feed Lu. This supports condition-specific mobilization, not general microbial superiority.
Support
Source:
barnett2018_supplement
Document S1 specifies the modified CAB recipe and screening methods. Table S1, Sheet1 rows 4–20, supplies triplicate mean/standard-deviation leaching data and original-feed composition; its fungal, bacterial, natural-community and salt rows remain distinct. These are source mass-based values, not solution concentrations or independent studies.
Partial
Source:
barnett2018
Discussion Sections 4–5 acknowledge background-community activity, unresolved acid-versus-complexation effects, slow kinetics and Si/Fe co-leaching. A matched proton-only test was future work. Cerium speciation and local redox explanations are proposed rather than demonstrated; the paper gives inconsistent Ce correlation statistics. Genus-level identifiers do not establish strain identity or each organism's exclusive causal contribution.
Guangxi indigenous culture-broth-associated rare-earth mobilization
bioleaching
Microbial
Cultivated communities from local pit wastewater were applied with their culture solutions to a separate Guangxi ore. La, Ce and Y were detected in leachates, and organic acids were measured in filtered culture liquids. This supports culture-broth-associated mobilization. It does not separate living-cell activity from accumulated metabolites, nutrients, medium salts or abiotic ion exchange, and does not demonstrate a purified rare-earth product, universal microbial advantage or industrial deployment.
Experimental Context & Analytical Limits:
Li et al. air-dried the natural feed at 20–35 °C, removed plant debris and mixed it by cone tetrad subdivision. Original ore was used for columns; a separate aliquot ball-milled for 2 min was used for stirred assays. Pit wastewater was first cultivated for 24 h in YEPD at initial pH 6, then transferred three times with 10 vol% preceding culture for 48 h at 30 °C and 160 rpm in Czapek (G1), sucrose (G2) or nutrient-broth (G3) media. Table 2's G3 medium contained 10 g/L peptone, 3 g/L beef extract and 5 g/L NaCl; G2 contained 4 g/L ammonium sulfate. Culture preparation began at pH 6 without subsequent adjustment. Stirred assays used 300 mL liquid in 500 mL flasks at 25 °C and 200 rpm. The common comparison used 50 vol% culture, 4 mL/g liquid-to-solid ratio and 60 min; later G3 series varied those factors. The column contained 1 kg original ore in five 200 g layers, with 70 vol% G3, nominal 5 mL/g and 117 h leaching. Triplicate groups and mean/standard-deviation reporting are stated. Water and 2/4 wt% ammonium sulfate were stirred comparators. A sterile uninoculated medium matched for nutrients, salts and pH was not reported, nor was a matched abiotic column. Ore sterilization and axenic community status were not established. The 18S-based community annotations do not verify species, strains, individual causal roles or the full bacterial community; the cited sequencing supplement was not accessible in this curation. No new taxon or sequence identifiers are asserted.
Li et al. air-dried the natural feed at 20–35 °C, removed plant debris and mixed it by cone tetrad subdivision. Original ore was used for columns; a separate aliquot ball-milled for 2 min was used for stirred assays. Pit wastewater was first cultivated for 24 h in YEPD at initial pH 6, then transferred three times with 10 vol% preceding culture for 48 h at 30 °C and 160 rpm in Czapek (G1), sucrose (G2) or nutrient-broth (G3) media. Table 2's G3 medium contained 10 g/L peptone, 3 g/L beef extract and 5 g/L NaCl; G2 contained 4 g/L ammonium sulfate. Culture preparation began at pH 6 without subsequent adjustment. Stirred assays used 300 mL liquid in 500 mL flasks at 25 °C and 200 rpm. The common comparison used 50 vol% culture, 4 mL/g liquid-to-solid ratio and 60 min; later G3 series varied those factors. The column contained 1 kg original ore in five 200 g layers, with 70 vol% G3, nominal 5 mL/g and 117 h leaching. Triplicate groups and mean/standard-deviation reporting are stated. Water and 2/4 wt% ammonium sulfate were stirred comparators. A sterile uninoculated medium matched for nutrients, salts and pH was not reported, nor was a matched abiotic column. Ore sterilization and axenic community status were not established. The 18S-based community annotations do not verify species, strains, individual causal roles or the full bacterial community; the cited sequencing supplement was not accessible in this curation. No new taxon or sequence identifiers are asserted.
Curated Evidence Points:
Support
Source:
li2025_indigenous
Sections 2.1–2.4, Figures 1–2 and Tables 1–2 identify the feed and laboratory treatments. Figures 5–8 report organic acids in filtered culture liquid and rare-earth-bearing leachates. These observations support association with the cultivated broth, without a matched sterile-medium control establishing how much mobilization required microbial metabolism during the leaching stage.
Partial
Source:
li2025_indigenous
Figure 6(a), at the shared 50 vol%, 4 mL/g, 60 min conditions, reports less mobilization for all three culture arms than for the ammonium sulfate comparators; G1 was only about 8–11% on the source's scale. The final 70 vol% G3, 5 mL/g, 60 min series reports La/Ce/Y values of 92.49/92.42/94.39%. These are source-reported percentages with an unresolved calculation basis, not independently validated recoveries. They must not be compared with the lower-dose controls as a matched demonstration of biological superiority.
Partial
Source:
li2025_indigenous
Printed page 1851 Equation 2 gives eta_x = (1 - C_x V) / (1000 omega_x M) times 100%, defining C_x in mg/L, V in L, omega_x as wt% and M in g. The subtraction and scale are not dimensionally consistent with those definitions; no silent replacement formula or reconstructed yield is adopted. Table 1 XRF values for La2O3, CeO2 and Y2O3 also differ from the separately reported elemental digestion inventories in Section 2.1 beyond simple oxide conversion. The operational ammonium-sulfate-extractable fraction and the remaining fraction by subtraction are not mineral-specific assays.
Partial
Source:
li2025_indigenous
Section 3.4 and Figure 8 show a separate 1 kg column trial, reporting a combined detectable La/Ce/Y leachate concentration peak near 390 mg/L at 33.5 h and a final source-scale percentage of 98.88% at 117 h. This is not an all-REE or isolated-product recovery yield. Original versus milled feed, flowing versus closed liquid and differing pH prevent attributing the column/flask difference solely to microorganisms. Figure 7(a)'s stirred pH plot is labeled 4 mL/g, while the compared selected leaching conditions use 5 mL/g.
Partial
Source:
li2025_indigenous
Figures 9–10 and Section 3.5 show source-assigned bulk phases and broadly similar before/after SEM morphology; the authors explicitly report no significant morphological difference apart from fewer fine particles. Relative XRD peak changes and the schematic in Figure 11 do not directly establish phase-specific dissolution, Ce(IV) reduction, Fe–O bond cleavage or an individual genus's mechanism. No such causal or redox pathway is accepted here. The 200 t example in the Introduction belongs to cited prior work, not this study's laboratory column.
Sources & References
-
barnett2018: Barnett, Palumbo-Roe and Gregory (2018), Comparison of Heterotrophic Bioleaching and Ammonium Sulfate Ion Exchange Leaching of Rare Earth Elements from a Madagascan Ion-Adsorption Clay; Minerals 8, 236; Sections 2–5, Figures 1–3 and Tables 1–5
https://doi.org/10.3390/min8060236 (accessed 2026-10-12) -
barnett2018_supplement: Barnett et al. (2018), Document S1 microbial screening and medium recipes, and Table S1 leaching workbook; publisher ZIP linked by the article XML
https://mdpi-res.com/d_attachment/minerals/minerals-08-00236/article_deploy/minerals-08-00236-s001.zip (accessed 2026-10-12) -
ncbi_aspergillus: NCBI Taxonomy, Aspergillus genus, taxon 5052; genus context only
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=5052 (accessed 2026-10-12) -
ncbi_bacillus: NCBI Taxonomy, Bacillus genus, taxon 1386; genus context only
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=1386 (accessed 2026-10-12) -
li2025_indigenous: Jiafeng Li, Junmeng Li, Lei Tian, Jian Wang, Yanfei Xiao and Zhiyuan Ma (2025), Extraction of rare earths from ion-adsorption type rare earth ore by indigenous microbial community; International Journal of Minerals, Metallurgy and Materials 32(8), 1848–1860; final publisher edition, Sections 2–4, Figures 1–11 and Tables 1–3
https://doi.org/10.1007/s12613-024-3071-9 (accessed 2026-10-12)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-12T08:32:06Z |
codex | CREATE | Added the natural clay-feed identity and primary-supported laboratory mobilization mechanism, preserving nonsterile controls, genus-only assignments, chemical comparisons and unresolved causal contributions. |
2026-10-12T10:02:31Z |
codex | EDIT | Added the separate Guangxi indigenous-culture broth experiment from the complete final Li et al. 2025 primary article, preserving chemical comparators, calculation and inventory conflicts, sequencing-access limits and laboratory-only association; earlier Madagascar claims remain unchanged. |
Record source: data/records/ion-adsorption-rare-earth-clay.yaml