Untitled

Murad, E.

doi:10.1023/a:1012635124874

Cited by 113 publications

(44 citation statements)

References 99 publications

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“…The presence of two Gaussian components in the starting goethite indicated that goethite existed as a range of particle sizes/crystallinity classes. The average hyperfine field of the sharp component in both the unreduced and the reduced sample was ∼48.5 T. This field value is typical of fine-grained goethite (22). The broad distribution with an average field of 43-44 T was assigned to goethite of lower crystallinity.…”

Section: Resultsmentioning

confidence: 91%

Microbial Reduction of Structural Fe(III) in Illite and Goethite

Dong

Kukkadapu

Fredrickson

et al. 2003

Environ. Sci. Technol.

134

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Microbial reduction of Fe(III) in illite was studied to evaluate the possibility of microbial utilization of Fe(III) in sedimentary clays and to determine the effects of bioreduction on clay composition and structure. A subsurface bacterium (Shewanella putrefaciens CN32) and illite separates (<0.2 µm) from St. Peter Formation sandstone in Ogle County, IL, were used in laboratory experiments. Illite suspensions buffered at pH 7 with bicarbonate were inoculated with CN32 and provided with H 2 as an electron donor. In selected treatments, anthraquinone-2,6-disulfonate (AQDS), was included as an electron shuttle to facilitate the bioreduction. Fe(II) production in inoculated treatments was determined by extraction with 0.5 N HCl and compared to uninoculated controls to establish the extent of biological reduction. The resulting solids were characterized by Mo ¨ssbauer spectroscopy and scanning and transmission electron microscopy (SEM and TEM). The characterization of the starting illite material revealed that it contained a minor component of goethite (R-FeOOH) in addition to fibrous illite. The starting material (both goethite and illite) contained 6% (w/ w) total Fe, and 82% of the total Fe was Fe(III). Approximately 30% of total Fe was associated with goethite. At the end of a 30-day incubation, residual goethite and illite remained. The extent of reduction was much greater in the presence of AQDS (25%) than in its absence (0%). Modeling of Mo ¨ssbauer spectra of the bioreduced material indicated that both goethite and illite were reduced but to a different extent. Additionally, TEM evidence suggested that there was a dramatic change in illite morphology upon bioreduction from fibrous needles to plates. The ability of bacteria to utilize Fe(III) in illite has important implications for microbial functions and survival mechanisms, as well as many geological processes, in the subsurface.

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Section: Resultsmentioning

confidence: 91%

Microbial Reduction of Structural Fe(III) in Illite and Goethite

Dong

Kukkadapu

Fredrickson

et al. 2003

Environ. Sci. Technol.

134

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“…The area (intensity) A T of the transmission peak can be expressed as (32) where I 0 and I 1 denote modified Bessel functions of the first kind, which first appeared in eq. 22.…”

Section: Quantitative Analysismentioning

confidence: 99%

“…Having realized this, the experts of the field have recently called the attention to the necessity of making use of temperature dependence for the analysis of iron-bearing oxide minerals [32] as well as to use the distribution-extracting methods in mineral analysis [27].…”

Section: Examples From Applications In Mineralogy and Geologymentioning

confidence: 99%

“…However, only two typical elementary patterns can be distinguished above 120 K, because the fast electron hopping at the B site smears out the observation of the separate microenvironments. However, below the Verwey transition, several magnetically split B-site patterns [32,67] can be observed, which can be used for the better identification of magnetite in rocks.…”

Section: Phase Analysis Of Rocksmentioning

confidence: 99%

“…Figure 47 [32] illustrates how important it is to find the appropriate external parameters at which the induced spectra are measured for the identification of different hydrous iron oxides in clay minerals [67]. Note that the predominant ferrihydrite phase (5Fe 2 O 3 ؒ9H 2 O) could not be identified from the standard pattern of illite alone.…”

Section: Phase Analysis Of Rocksmentioning

confidence: 99%

See 2 more Smart Citations

Critical review of analytical applications of Mössbauer spectroscopy illustrated by mineralogical and geological examples (IUPAC Technical Report)

Кузманн¹,

Nagy²,

Vértes³

2003

Pure and Applied Chemistry

120

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We have developed a new terminology for Mössbauer pattern analysis in order to enhance the performance of qualitative analysis by Mössbauer spectroscopy. In this approach, Mössbauer parameters are considered as a function of a number of externally adjusted experimental parameters at which the spectrum has been recorded. The basis of analytical classification is the microenvironment, which is determined by an assembly of atoms causing the same hyperfine interactions at one particular class of the Mössbauer probe atoms.Since Mössbauer spectroscopy measures hyperfine interactions very sensitively, the microenvironment presents itself as a fundamental concept for analytical purposes. Our approach can also help to systematize the Mössbauer data for the identification of individual physicochemical species from the corresponding patterns present in the spectrum.

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Superparamagnetic Particles

Mørup

Hansen

2007

Handbook of Magnetism and Advanced Magnetic Materials

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The magnetic properties of nanoparticles are reviewed with special emphasis on magnetic relaxation phenomena. After an introduction to superparamagnetic relaxation phenomena, we give a brief introduction to synthesis of nanoparticles and how they can be characterized by standard techniques such as X‐ray diffraction, electron microscopy, and other techniques. We then describe how one can study magnetic relaxation phenomena in noninteracting nanoparticles by different experimental techniques such as DC and AC magnetization measurements, Mössbauer spectroscopy, and neutron scattering. Subsequently, the influence of interparticle interactions on the relaxation is discussed, and it is shown that both magnetic dipole and exchange interactions between nanoparticles can have a significant influence on the relaxation phenomena. Finally, we discuss the magnetic structure in nanoparticles and how spin canting and transverse relaxation can influence the magnetic properties of nanoparticles.

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Untitled

Cited by 113 publications

References 99 publications

Microbial Reduction of Structural Fe(III) in Illite and Goethite

Microbial Reduction of Structural Fe(III) in Illite and Goethite

Critical review of analytical applications of Mössbauer spectroscopy illustrated by mineralogical and geological examples (IUPAC Technical Report)

Superparamagnetic Particles

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