Palygorskite mineral
Palygorskite is the fibrous hydrated magnesium-aluminium silicate listed by IMA as (Mg,Al)2Si4O10(OH).4H2O, grandfathered status G, original-description year 1862. That year is not an approval accession. This mineral owner is distinct from a commercial attapulgite clay commodity, the smectite group and other clay specimens in the same experiment. The accepted primary evidence concerns size-separated, chemically cleaned PFl-1 material, not an untreated natural assemblage or an industrial recovery feed. No constituent criticality designation is inherited.
Microbial & Biochemical Mechanisms (2)
CN32-associated iron reduction in pretreated PFl-1
redox transformation
Microbial
Associated Organisms:
Shewanella putrefaciens CN-32 (NCBITaxon:319224)
Shewanella putrefaciens CN32 increased measured Fe(II) in the pretreated palygorskite specimen relative to no-cell controls. Added AQDS increased the final extent. The experiment supports conditional iron reduction, not substantial dissolved-iron recovery or a mineral-specific electron-transfer protein.
Experimental Context & Analytical Limits:
PFl-1 from the Clay Minerals Society Source Clays Repository originated in the Hawthorn Formation, Georgia-Florida border. The 0.02-0.5 micrometre fraction was treated with dithionite-citrate-bicarbonate for ten minutes, acid-washed, homoionized and reoxidized before use. Methods specify 96-hour reoxidation whereas Figure 5 describes 72 hours; this discrepancy is unresolved. Pasteurized cleaned clay at 7 g/L was incubated with washed CN32 cells at approximately 1.92 x 10^7 cells/mL, nominal 0.2 mM lactate, 30 mM bicarbonate buffer at pH 7, with or without 0.1 mM AQDS. Duplicate anoxic laboratory tubes were held at 37 degrees C and shaken at 60 rpm for approximately two weeks. Equal buffer replaced cells in abiotic controls. Phenanthroline measured Fe(II); these are resting-cell buffer experiments, not demonstrated growth on palygorskite.
PFl-1 from the Clay Minerals Society Source Clays Repository originated in the Hawthorn Formation, Georgia-Florida border. The 0.02-0.5 micrometre fraction was treated with dithionite-citrate-bicarbonate for ten minutes, acid-washed, homoionized and reoxidized before use. Methods specify 96-hour reoxidation whereas Figure 5 describes 72 hours; this discrepancy is unresolved. Pasteurized cleaned clay at 7 g/L was incubated with washed CN32 cells at approximately 1.92 x 10^7 cells/mL, nominal 0.2 mM lactate, 30 mM bicarbonate buffer at pH 7, with or without 0.1 mM AQDS. Duplicate anoxic laboratory tubes were held at 37 degrees C and shaken at 60 rpm for approximately two weeks. Equal buffer replaced cells in abiotic controls. Phenanthroline measured Fe(II); these are resting-cell buffer experiments, not demonstrated growth on palygorskite.
Curated Evidence Points:
Support
Source:
bishop_2010_thesis
Methods 2.1-2.2, Results 3.4 printed p16 and Figure 8H (PDF p54; specimen label PFl-1) support 2.65% and 4.17% Fe(III) reduction without and with AQDS, respectively, and a near-baseline no-cell curve. These are source-reported reduction extents in the prepared material, not percentages of clay dissolved or product recovered. Prose cites Figure 8F for PFl-1, but the actual nine-panel figure and its caption identify H; F is ARG-24.
Partial
Source:
bishop_2010_thesis
Figure 1F shows the original magnetite impurity and the treated diffraction pattern; Figure 5 includes PFl-1 after cleaning. These support the authors' assignment of the remaining reducible iron to cleaned clay, within method detection limits, not universal phase purity. DCB and acid pretreatment can alter the specimen. Table 2 reports different total-iron determinations, and the thesis abstract contains inconsistent cross-mineral rankings; neither a universal reduction ranking nor a harmonized iron composition is asserted.
Partial
Source:
bishop_2010_thesis
Table 3 (printed p37, PDF p44) reports the same dissolved Fe value, 0.002 mmol/L, and Al value, 0.024 mmol/L, for PFl-1 control and bioreduced plus-AQDS material. Si, Mg and K differ, but the stated DCP error is +/-0.03 mmol/L. Thus the general prose about greater dissolved Fe and Al in bioreduced clays must not be transferred to PFl-1. Figure 10 shows declining PFl-1 colony counts, and XRD does not show a discernible new PFl-1 phase; no growth promotion, new mineral identity or bulk iron-extraction yield is claimed.
Context_only
Source:
bishop_2011_lineage
The journal metadata/abstract describe the same authors' clay reduction and technetium research. Thesis-specific conditions and figure numbers are not attributed to the unavailable journal full text; this is one research lineage.
Abiotic technetium removal by washed bioreduced PFl-1
redox transformation
A separate reaction used washed, pasteurized bioreduced PFl-1 as an Fe(II)-bearing reductant. Loss of aqueous technetium accompanied Fe(II) oxidation. Microorganisms prepared the reductant in the preceding arm; this assay is an abiotic reaction, and the source interprets technetium immobilization as Tc(VII) reduction to Tc(IV).
Experimental Context & Analytical Limits:
Methods 2.3-2.4.5 and Table 1 specify anoxic 10 mL reactions in 20 mL bottles, 30 mM PIPES at pH 7, nominal initial 50 micromolar technetium-99 supplied as ammonium pertechnetate, and 0.5 mM PFl-1-associated Fe(II). The bioreduced solid was washed and pasteurized before technetium addition. No-clay technetium and no-technetium clay controls were included. Liquid-scintillation analysis of centrifuged supernatant measured remaining aqueous activity; phenanthroline monitored Fe(II). Bottles were gently hand-shaken daily. The reported initial technetium concentration conflicts with the approximately 80-scale starting points in Figures 11 and 13; the prose also ambiguously states a 0.5 micromolar subsequent spike. No precise technetium capacity is adopted.
Methods 2.3-2.4.5 and Table 1 specify anoxic 10 mL reactions in 20 mL bottles, 30 mM PIPES at pH 7, nominal initial 50 micromolar technetium-99 supplied as ammonium pertechnetate, and 0.5 mM PFl-1-associated Fe(II). The bioreduced solid was washed and pasteurized before technetium addition. No-clay technetium and no-technetium clay controls were included. Liquid-scintillation analysis of centrifuged supernatant measured remaining aqueous activity; phenanthroline monitored Fe(II). Bottles were gently hand-shaken daily. The reported initial technetium concentration conflicts with the approximately 80-scale starting points in Figures 11 and 13; the prose also ambiguously states a 0.5 micromolar subsequent spike. No precise technetium capacity is adopted.
Curated Evidence Points:
Support
Source:
bishop_2010_thesis
Figure 11F (PDF p59) separately plots PFl-1 aqueous technetium decline, Fe(II) decline and the two controls, including repeated technetium additions. This supports reactivity of the prepared Fe(II)-bearing solid. It does not prove that only newly biogenic Fe(II) reacts; Results 3.5 explicitly considers reaction of pre-existing Fe(II).
Partial
Source:
bishop_2010_thesis
The direct Tc-bearing microscopy in Figures 14-15 concerns CCa-2 and ISCz-1, not PFl-1. Aqueous activity loss and Fe oxidation are consistent with the source redox interpretation, but PFl-1-specific Tc oxidation-state spectroscopy, product crystal structure, isolated recovered product and long-term reoxidation resistance are not established here. PIPES alone decreased aqueous Tc after about 800 hours; the source limits or refreshes the buffer in longer experiments. No field deployment, purified-metal recovery or source-wide Fe/Tc ratio is inferred.
Sources & References
-
ima_2026_09: IMA-CNMNC. The New IMA List of Minerals, September 2026, Palygorskite row, PDF p164 and list definitions. Retained original re-inspected on the access date.
https://cnmnc.units.it/files/editor/IMA_Master_List_(2026-09).pdf (accessed 2026-10-14) -
handbook_palygorskite: Handbook of Mineralogy. Palygorskite, version 1.2 (2001), complete one-page identity and structure.
https://www.handbookofmineralogy.org/pdfs/palygorskite.pdf (accessed 2026-10-14) -
bishop_2010_thesis: Bishop, Michael Edward (2010). Microbial Reduction of Fe(III) in Multiple Clay Minerals by Shewanella putrefaciens and Reactivity of Bioreduced Clay Minerals toward Tc(VII) Immobilization. Miami University MS thesis, OhioLINK miami1291059786. Complete 64-page original; printed pp4-24, Tables 1-3, Figures 1-15. The title-page spelling and Methods identify S. putrefaciens CN32.
https://etd.ohiolink.edu/acprod/odb_etd/ws/send_file/send?accession=miami1291059786&disposition=inline (accessed 2026-10-14) -
bishop_2011_lineage: Bishop, Dong, Kukkadapu, Liu and Edelmann (2011). Bioreduction of Fe-bearing clay minerals and their reactivity toward pertechnetate (Tc-99). Geochimica et Cosmochimica Acta 75:5229-5246. DOI metadata and publisher abstract only; full journal text was not acquired. Treated as a related publication of the thesis research, not an independent replication or the source of curated measurements.
https://doi.org/10.1016/j.gca.2011.06.034 (accessed 2026-10-14) -
ncbi_cn32: NCBI Taxonomy 319224, Shewanella putrefaciens CN-32, strain rank; parent species 24. Current XML inspected. This maps the reported strain label without authenticating the experimental stock.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=319224&mode=Info (accessed 2026-10-14)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-14T18:02:49.045937Z |
codex (GPT-6; codex) | CREATE | Created mineral owner from the complete Bishop2010 primary thesis, separating controlled microbial iron reduction from the subsequent abiotic technetium assay and preserving specimen, null and source-conflict limits. |
Record source: data/records/palygorskite.yaml