Natural silica-sand feed primary resource
Naturally occurring quartz-rich sand or disaggregated sandstone used as an industrial-mineral feed, represented here by two distinct English quarry samples. Yahaya's Silica 2 was a purple-red Oakamoor/Moneystone rock sample disaggregated to sand-grade powder; Silica 3 was yellow, uncemented Lower Greensand from Grandcourt near King's Lynn. The latter's XRD was dominated by quartz with minor phases assigned as kaolinite and feldspar. These are heterogeneous geological feeds, not the mineral species quartz, elemental silicon, spent foundry sand or a purity-defined silica product. The two samples' compositions and assay outcomes are not pooled. No constituent's criticality designation is transferred to this resource.
Microbial & Biochemical Mechanisms (1)
Resting-cell-associated reduction of iron in natural silica sand
redox transformation
Microbial
Associated Organisms:
Shewanella putrefaciens (NCBITaxon:24)
Washed, viable Shewanella putrefaciens cells designated CIP8040 were associated with increased HCl-extractable Fe(II) in anaerobic silica-sand microcosms relative to the displayed blank. This is consistent with reduction of feed-associated Fe(III), with lactate supplied as an electron donor. It does not establish a particular iron-mineral source, a unique electron-transfer pathway, dissolved-only iron release, isolated iron recovery or industrial deployment.
Experimental Context & Analytical Limits:
The accepted core experiment used the source's Silica 3 from Grandcourt, collected in July 2008; its feed identity is distinct from Oakamoor Silica 2. Chapter 2 describes a nongrowth assay with washed stationary-phase cells, 80 mL minimal saline medium containing 0.9% NaCl and normally 10 mM lactate, in sealed, sterilized bottles purged with oxygen-free N2. Working pH was described as approximately 7.1-7.3, with dark incubation and 60 rpm shaking. The cell-density comparison used 2.5 g Silica 3, 3.5 or 7 mL stock suspension and 30 degrees C; the stock concentration was reported as 1.2 plus or minus 0.4 times 10^8 cells or CFU per mL, not the final reactor cell density. Its figure reports standard errors for three replicates. The separate AQDS comparison used 2.4 g Silica 3 and 4 mL stock cells at 30 degrees C, with or without the generally specified 100 micromolar AQDS. These arms are not pooled as identical assays. General methods describe blanks as cell-free or cell-and-donor-free without clearly mapping the two formulations to every figure; therefore a fully matched lactate-containing abiotic control is not assumed. For Fe(II) analysis, 1 mL unfiltered sample was mixed with 1 mL 2 M HCl for about 24 hours, filtered at 0.2 micrometres and analyzed using 1,10-phenanthroline at 510 nm. The endpoint includes acid-extractable solid-associated as well as soluble Fe(II). These laboratory microcosms do not establish a complete mass balance or a recovered product yield.
The accepted core experiment used the source's Silica 3 from Grandcourt, collected in July 2008; its feed identity is distinct from Oakamoor Silica 2. Chapter 2 describes a nongrowth assay with washed stationary-phase cells, 80 mL minimal saline medium containing 0.9% NaCl and normally 10 mM lactate, in sealed, sterilized bottles purged with oxygen-free N2. Working pH was described as approximately 7.1-7.3, with dark incubation and 60 rpm shaking. The cell-density comparison used 2.5 g Silica 3, 3.5 or 7 mL stock suspension and 30 degrees C; the stock concentration was reported as 1.2 plus or minus 0.4 times 10^8 cells or CFU per mL, not the final reactor cell density. Its figure reports standard errors for three replicates. The separate AQDS comparison used 2.4 g Silica 3 and 4 mL stock cells at 30 degrees C, with or without the generally specified 100 micromolar AQDS. These arms are not pooled as identical assays. General methods describe blanks as cell-free or cell-and-donor-free without clearly mapping the two formulations to every figure; therefore a fully matched lactate-containing abiotic control is not assumed. For Fe(II) analysis, 1 mL unfiltered sample was mixed with 1 mL 2 M HCl for about 24 hours, filtered at 0.2 micrometres and analyzed using 1,10-phenanthroline at 510 nm. The endpoint includes acid-extractable solid-associated as well as soluble Fe(II). These laboratory microcosms do not establish a complete mass balance or a recovered product yield.
Curated Evidence Points:
Support
Source:
yahaya2012
Chapter 2 sections 2.2.2, 2.4.3-2.4.5 and 2.5.7, printed pages 31-40 (PDF pages 50-59), establish the separate feeds, cell preparation and extraction assay. Chapter 5 cell-density comparison, printed pages 110-111 (PDF pages 129-130; Figure 5.2), shows greater extractable Fe(II) with 7 mL than with 3.5 mL CIP8040 suspension and a lower, nonzero blank. The text reports day-one concentrations of 0.24 and 0.12 mmol/L respectively. These are assay concentrations, not rates or percentages recovered. The differing inoculum volumes and incompletely specified blank composition limit a unique causal interpretation.
Partial
Source:
yahaya2012
Chapter 5 printed pages 111-115 (PDF pages 130-134), AQDS-presence comparison Figure 5.3 and the AQDS/NOM/no-shuttle comparison Figure 5.5, show little early AQDS benefit and only modest later differences in Silica 3. The Figure 5.3 text reports 0.224 mmol/L with AQDS and 0.186 mmol/L without it after 15 days. This does not support a universal requirement for, or large enhancement by, the added shuttle. Figure 5.4 is excluded from a feed-specific quantitative inference because its surrounding discussion concerns Silica 3 while its caption says Silica Sand 2. Proposed direct contact, pore accessibility and cell-surface inhibition were not independently established by these comparisons.
Partial
Source:
yahaya2012
Chapter 5 printed pages 109-110 (PDF pages 128-129), strain-screen Figure 5.1, instead concerns 2.5 g Oakamoor Silica 2 with 10 mM lactate and 100 micromolar AQDS at a caption-specified 20 degrees C. Its four displayed curves include a much lower response for source-designated S. loihica than for the other tested cultures. This separate screen cannot establish identical behavior across strains or be transferred quantitatively to the Grandcourt 30-degree-C experiment. The generic culture list is not used to invent an additional tested silica strain.
Partial
Source:
yahaya2012
Chapter 5 printed pages 121-126 (PDF pages 140-145), Figures 5.10-5.15 and Tables 5.1-5.2, constrain the mineralogical interpretation. Before/ after XRD of Silica 3 did not show an obvious new crystalline product; FTIR changes also occurred in the blank. Local EDX lists Fe in the blank but not the biotreated table, without a detection limit or bulk recovery balance. This is not complete iron removal. SEM images show surface differences but do not identify a uniquely dissolved iron phase. The displayed Mossbauer spectrum is of untreated Silica 3 only, not a measured before/after oxidation-state conversion. None of these observations establishes purified silica quality or a specific genetic mechanism. The deposited document's editorial uncertainties further warrant preserving these narrow interpretations.
Sources & References
-
yahaya2012: Yahaya, S. Bacterial removal of iron impurities to increase the quality and value of industrial minerals. Newcastle University PhD thesis, repository issue year 2012; cover and declaration dated September 2011. Complete 297-page official PDF acquired; this claim assessment covers Chapter 2 methods and Chapter 5 silica microcosms, including all its figures and tables. The deposited artifact visibly retains tracked edits, comments and overlapping section/figure numbers. Printed pages and figure subjects below disambiguate locators; this is not a clean journal edition.
https://theses.ncl.ac.uk/jspui/handle/10443/1346 (accessed 2026-10-15) -
ncbi_putrefaciens: NCBI Taxonomy 24, Shewanella putrefaciens, current species-level record. This identifier resolves the species name, not a verified genome or the identity of the thesis's particular stored culture.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=24&mode=Info (accessed 2026-10-15) -
jcm_cip8040: RIKEN JCM catalogue, Shewanella putrefaciens JCM 20190T, listing CIP 80.40 among equivalent type-strain collection designations. This corroborates the thesis spelling CIP8040 as a culture designation; it does not verify that the experimental culture was independently sequence-confirmed.
https://www.jcm.riken.jp/cgi-bin/jcm/jcm_number?JCM=20190 (accessed 2026-10-15)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-15T00:06:20.077904+00:00 |
codex (GPT-6; codex) | CREATE | Curated the distinct natural silica-sand resource and a bounded primary resting-cell iron-redox assay, preserving quarry-specific conditions, extraction endpoint, controls, null effects and deposited-source limits. |
Record source: data/records/silica-sand.yaml