Iron Oxides in Laboratory

Schwertmann, U.; Cornell, R. M.

doi:10.1097/00010694-199311000-00012

Cited by 522 publications

(800 citation statements)

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“…Schwertmannite was prepared using a modified version of the method described by (22). The precipitate was washed six-times in 18.2 MΩ water, freeze dried and stored under a nitrogen atmosphere until required.…”

Section: Magnetite Formationmentioning

confidence: 99%

Optimizing Cr(VI) and Tc(VII) Remediation through Nanoscale Biomineral Engineering

Cutting

Coker

Telling

et al. 2010

Environ. Sci. Technol.

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To optimise the production of biomagnetite for the bioremediation of metal oxyanion contaminated waters, the reduction of aqueous Cr(VI) to Cr(III) by two biogenic magnetites and a synthetic magnetite was evaluated under batch and continuous flow conditions. Results indicate that nano-scale biogenic magnetite produced by incubating synthetic schwertmannite powder in cell suspensions of Geobacter sulfurreducens is more efficient at reducing Cr(VI) than either biogenic nano-magnetite produced from a suspension of ferrihydrite "gel" or synthetic nano-scale Fe 3 O 4 powder.Although X-ray Photoelectron Spectroscopy (XPS) measurements obtained from postexposure magnetite samples reveal that both Cr(III) and Cr(VI) are associated with nanoparticle surfaces, X-ray Magnetic Circular Dichroism (XMCD) studies indicate that some Cr(III) has replaced octahedrally coordinated Fe in the lattice of the magnetite.Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) measurements of total aqueous Cr in the associated solution phase indicated that, although the majority of Cr(III) was incorporated within or adsorbed to the magnetite samples, a proportion (~10-15 %) was released back into solution. Studies of Tc(VII) uptake by magnetites produced via the different synthesis routes also revealed significant differences between them as regards effectiveness for remediation. In addition, column studies using a γ-camera to obtain real time images of a 99m Tc(VII) radiotracer were performed to visualise directly the relative performances of the magnetite sorbents against ultra-trace concentrations of 2 metal oxyanion contaminants. Again, the magnetite produced from schwertmannite proved capable of retaining more (~20 %) 99m Tc(VII) than the magnetite produced from ferrihydrite, confirming that biomagnetite production for efficient environmental remediation can be fine-tuned through careful selection of the initial Fe(III) mineral substrate supplied to Fe(III)-reducing bacteria.3

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Section: Magnetite Formationmentioning

confidence: 99%

Optimizing Cr(VI) and Tc(VII) Remediation through Nanoscale Biomineral Engineering

Cutting

Coker

Telling

et al. 2010

Environ. Sci. Technol.

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“…A substituição isomórfica (SI) do Fe pelo Al ou, em menor escala, por outros metais na grade cristalina dos óxidos de Fe, depende basicamente da disponibilidade destes durante o processo de formação (Schwertmann & Cornell, 1991). Em condições normais, isto ocorre com freqüência, porque, geralmente, há disponibilidade de Al no sistema (Schwertmann et al, 2000), sendo possível o átomo de Al apresentar a mesma valência e tamanho similares aos do Fe (r = 0,053 nm para o Al 3+ e r = 0,064 nm para o Fe 3+ ), podendo, então, substituí-lo na posição octaedral nos óxidos de Fe.…”

Section: Introductionunclassified

Relações entre a substituição isomórfica de Fe por Al e as características químicas e mineralógicas de hematitas sintéticas

Sambatti¹,

Costa²,

Muniz³

et al. 2002

Rev. Bras. Ciênc. Solo

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“…The set of Fe reference 191 standards included ferrihydrite, goethite, lepidocrocite, magnetite, green rust-chloride, green 192 rust-sulfate, green rust-carbonate and hematite. Each of these materials was synthesized 193 following the procedures of Schwertmann and Cornell [1991]. We can use the NMR measurements on the same iron minerals reported in Keating and Knight 209 [2007] for comparison.…”

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Geochemical Controls on Nuclear Magnetic Resonance Measurements

Knight¹

2008

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Proton nuclear magnetic resonance (NMR) is used in the Earth Sciences as a means of obtaining information about the molecular-scale environment of fluids in porous geological materials. Laboratory experiments were conducted to advance our fundamental understanding of the link between the NMR response and the geochemical properties of geological materials. In the first part of this research project, we studied the impact of both the surface-area-to-volume ratio (S/V) of the pore space and the surface relaxivity on the NMR response of fluids in sandclay mixtures. This study highlighted the way in which these two parameters control our ability to use NMR measurements to detect and quantify fluid saturation in multiphase saturated systems. The second part of the project was designed to explore the way in which the mineralogic form of iron, as opposed to simply the concentration of iron, affects the surface relaxation rate and, more generally, the NMR response of porous materials. We found that the magnitude of the surface relaxation rate was different for the various iron-oxide minerals because of changes in both the surface-area-to-volume ratio of the pore space, and the surface relaxivity. Of particular significance from this study was the finding of an anomalously large surface relaxivity of magnetite compared to that of the other iron minerals. Differences in the NMR response of iron minerals were seen in column experiments during the reaction of ferrihydrite-coated quartz sand with aqueous Fe(II) solutions to form goethite, lepidocrocite and magnetite; indicating the potential use of NMR as a means of monitoring geochemical reactions. The final part of the research project investigated the impact of heterogeneity, at the pore-scale, on the NMR response. This work highlighted the way in which the geochemistry, by controlling the surface relaxivity, has a significant impact on the link between NMR data and the microgeometry of the pore space. Introduction and Research ObjectivesNuclear magnetic resonance (NMR) is a measurement technique, developed in the 1940's, that can provide an incredible amount of information about molecular-scale processes and properties in a wide range of materials. Of specific interest in our research is proton NMR, which investigates the molecular-scale environment of hydrogen nuclei. In the Earth sciences proton NMR is most commonly used to measure the response of water in porous geological materials, as a way of obtaining information about the water content and microgeometry of the water-filled regions of the pore space. Despite many years of the use and study of NMR for borehole logging in the petroleum industry there still remain key questions about the basic mechanisms governing NMR relaxation measurements. As a result, the potential of NMR as a means of determining and studying the physical, chemical and biological properties of Earth materials is far from being fully realized. 2The goal of our research was to advance the fundamental understanding of the link between the NM...

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Iron Oxides in Laboratory

Cited by 522 publications

References 0 publications

Optimizing Cr(VI) and Tc(VII) Remediation through Nanoscale Biomineral Engineering

Optimizing Cr(VI) and Tc(VII) Remediation through Nanoscale Biomineral Engineering

Relações entre a substituição isomórfica de Fe por Al e as características químicas e mineralógicas de hematitas sintéticas

Geochemical Controls on Nuclear Magnetic Resonance Measurements

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