Adsorption of potential-determining ions at the ferric oxide-aqueous electrolyte interface

The thermal decomposition of synthetic a-FeOOH in air has becn studied by X~ray powder diffraction (XRD), IR spectroscopy. transmission electron microscopy, and nitrogen adsorption. Three stages may be differentiated during the course ofthe reaction: (i) 200-250°C; slit-shaped micropores of nearly equal width, about 1.4 nm, are formed along the elongated direction of the lath-shaped acicular mícrocrystals of the hematite producÍS, the highest surface area is obtained on a a-FeOOH decomposed at 250°C; (ii) 300-600°C; an internal sintering occurs within the microcrystals transforming the micropores into dosed spherical mesopores with the consequent significant decrease in surface area; and (iii) above 600°C; interparticle sintering takes place and no valuable porosity is detected. Particle shape effects are shown to be the reason for the differences in the IR spectra and for the nonuniform broadening of the XRD peaks observed in the hematite products.

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“…(9). Electron micrographs showed acicular morphology for the particles, with an average size of about 0.4 X 0.08 JLffi.…”

Section: Malerialsmentioning

confidence: 92%

Pore structure of thermally treated goethite (α-FeOOH)

Rendon

Cornejo

Arambarri

et al. 1983

Journal of Colloid and Interface Science

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“…LM growth medium containing 0.6% NaCl and 20 mM lactate (Meyers & Nealson, 1988) was used for metal reduction experiments. Amorphous manganese oxide (Lovely & Phillips, 1988) and FeOOH (Atkinson et al, 1967) were prepared as described elsewhere. Inocula were grown aerobically in LB liquid medium at 30 "C, harvested by centrifugation, and adjusted to an inoculum size of approximately 2.0 x lo7 (equivalent to OD,,, = 0.2) bacterial cells per ml in LM medium containing either ferric or manganese oxides.…”

Section: Methodsmentioning

confidence: 99%

Shewanella amazonensis sp. nov., a novel metal-reducing facultative anaerobe from Amazonian shelf muds

Venkateswaran

Dollhopf

Aller

et al. 1998

International Journal of Systematic Bacteriology

119

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A new bacterial species belonging t o the genus Shewanella is described on the basis of phenotypic characterization and sequence analysis of its 165 rRNAencoding and gyrase B (gyrB) genes. This organism, isolated from shallowwater marine sediments derived from the Amazon River delta, is a Gramnegative, motile, polarly flagellated, facultatively anaerobic, rod-shaped eubacterium and has a G+C content of 51.7 mol0/o. Strain SB2BT is exceptionally active in the anaerobic reduction of iron, manganese and sulfur compounds. SB2BT grows optimally at 35 "C, with 1-3% NaCl and over a pH range of 7-8. Analysis of the 165 rDNA sequence revealed a clear affiliation between strain SB2BT and members of the gamma subclass of the class Proteobacteria. High similarity values were found with certain members of the genus Shewanella, especially with Shewanella putrefaciens, and this was supported by cellular fatty acid profiles and phenotypic characterization. DNA-DNA hybridization between strain SB2BT and its phylogenetically closest relatives revealed low similarity values (246-4207 %) which indicated species status for strain SB2BT. That SB2BT represents a distinct bacterial species within the genus Shewanella is also supported by gyrB sequence analysis. Considering the source of the isolate, the name Shewanella amazonensis sp. nov. is proposed and strain SB2BT (= ATCC 7003293 is designated as the type strain.

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“…Goethite was prepared using a slightly modified version of Atkinson et al (1967). Ferric nitrate was combined with concentrated sodium hydroxide in the absence of CO 2 .…”

Section: Synthesis Of Iron (Hydr)oxide-coated Sandsmentioning

confidence: 99%

Influence of Uranyl Speciation and Iron Oxides on Uranium Biogeochemical Redox Reactions

Stewart

Amos

Nico

et al. 2011

Geomicrobiology Journal

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Uranium is a pollutant of concern to both human and ecosystem health. Uranium's redox state often dictates its partitioning between the aqueous-and solid-phases, and thus controls its dissolved concentration and, coupled with groundwater flow, its migration within the environment. In anaerobic environments, the more oxidized and mobile form of uranium (UO 2 2+ and associated species) may be reduced, directly or indirectly, by microorganisms to U(IV) with subsequent precipitation of UO 2 . However, various factors within soils and sediments may limit biological reduction of U(VI), inclusive of alterations in U(VI) speciation and competitive electron acceptors. Here we elucidate the impact of U(VI) speciation on the extent and rate of reduction with specific emphasis on speciation changes induced by dissolved Ca, and we examine the impact of Fe(III) (hydr)oxides (ferrihydrite, goethite and hematite) varying in free energies of formation on U reduction. The amount of uranium removed from solution during 100 h of incubation with S. putrefaciens was 77% with no Ca or ferrihydrite present but only 24% (with ferrihydrite) and 14% (no ferrihydrite) were removed for systems with 0.8 mM Ca.Imparting an important criterion on uranium reduction, goethite and hematite decrease the dissolved concentration of calcium through adsorption and thus tend to diminish the effect of calcium on uranium reduction. Dissimilatory reduction of Fe(III) and U(VI) can proceed through different enzyme pathways, even within a single organism, thus providing a potential second means by which Fe(III) bearing minerals may impact U(VI) reduction. We quantify rate coefficients for simultaneous dissimilatory reduction of Fe(III) and U(VI) in systems varying in Ca concentration (0 to 0.8 mM), and using a mathematical construct implemented with the reactive transport code MIN3P, we reveal the predominant influence of uranyl speciation, 2 specifically the formation of uranyl-calcium-carbonato complexes, and ferrihydrite on the rate and extent of uranium reduction in complex geochemical systems.3

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Adsorption of potential-determining ions at the ferric oxide-aqueous electrolyte interface

Cited by 596 publications

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Pore structure of thermally treated goethite (α-FeOOH)

Pore structure of thermally treated goethite (α-FeOOH)

Shewanella amazonensis sp. nov., a novel metal-reducing facultative anaerobe from Amazonian shelf muds

Influence of Uranyl Speciation and Iron Oxides on Uranium Biogeochemical Redox Reactions

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