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Stucki, Joseph W. Wilkinson, Henry T. Gates, Will Peter 2011-05-07T14:29:04Z 2011-05-07T14:29:04Z 10000-01-01 1994 The ability of bacteria to reduce smectite structural Fe and the effect microbial reduction has on clay swelling, flow behavior, and the crystal structure was studied to better understand the reduction process. Structural Fe reduction by combinations of Pseudomonas bacteria is a diffusion driven process in which extracellular reductants may be involved in the transfer of electrons from the solution phase to crystalline Fe. The absolute magnitude of structural Fe(II) depended on the total structural Fe content of the clay mineral. Reduction of structural Fe by various bacteria cultures decreased the swelling pressure of the Fe-bearing clays studied, as measured by the gravimetric water content (m$\sb{\rm w}$/m$\sb{\rm c}$). The depression of m$\sb{\rm w}$/m$\sb{\rm c}$ by microbial reduction of structural Fe(II) was greater at Fe(II) contents less than 0.4 mmol g$\sp{-1}$ than in chemically-reduced smectites. The presence of structural Fe(II) apparently overcomes the opposing effect of organics on the ability of clay gels to retain water. The flow behavior of microbially-reduced smectite suspensions depended on smectite, medium used, incubation time, and Fe(II) content. The yield stress ($\sigma\sb{\rm e}$) for the Fe-bearing smectite suspensions increased with increasing Fe(II) content above 0.2 mmol Fe(II), indicating increased inter-particle forces of attraction. A general direct relationship existed between $\sigma\sb{\rm e}$ and the plastic viscosity ($\eta\sb{\rm pl}$) for the Fe-bearing smectite suspensions. Multi nuclear ($\sp{29}$Si, $\sp{27}$Al, and $\sp{23}$Na) magic-angle sample spinning nuclear magnetic resonance (MAS NMR) of dithionite- and microbially-reduced montmorillonite revealed that reduction of structural Fe caused reversible structural distortions in the tetrahedral sheet, lifted the paramagnetic effect of Fe(III) on quadrupolar nuclei, and resulted in an increased association of charge-balancing cations with the clay surface. The structural changes that occur upon reduction of structural Fe are consistent with numerous studies detailing the effects of reduction of structural Fe(III) on physical and chemical properties of smectites. Made available in DSpace on 2011-05-07T14:29:04Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9512369.pdf: 7386651 bytes, checksum: 35a5f570e3ab77c74b1e390a3d87e843 (MD5) Previous issue date: 1994 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T15:07:16Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:32:18-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission Restricted to the U of I community indefinitely during batch ingest of legacy ETDs U of I Only AAI9512369 (UMI)AAI9512369 http://hdl.handle.net/2142/23840 eng Copyright 1994 Gates, Will Peter Biology, Microbiology Mineralogy Biogeochemistry Physical chemistry of microbially-reduced smectites text Biology, Microbiology Mineralogy Biogeochemistry Biology, Microbiology Mineralogy Biogeochemistry University of Illinois at Urbana-Champaign Dissertation Ph.D.