The Behavior of Co, Ni, Zn, Cu, Mn, and Cr in Magnetite during Alteration to Maghemite and Hematite

Sidhu, P. S.; Gilkes, R. J.; Posner, A. M.

doi:10.2136/sssaj1980.03615995004400010028x

Cited by 59 publications

(42 citation statements)

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“…Landers et al (2009) observed Ni migration in natural goethite samples because of thermal treatment. In contrast, Sidhu et al (1980) emphasized that during thermal transformation of maghemite into hematite, element ejection mainly occurs with divalent ions that exhibit a lower valence and larger ionic radii than Fe 3+ , a situation not observed in this experiment.…”

Section: Available Fe and Al In 1 Mol L -1 Kclcontrasting

confidence: 72%

“…In other words, the higher the content of chemical elements, the higher the energy necessary to eject or redistribute them in the mineral crystalline structure. When samples with different IS are exposed to the same temperature, the sample that has higher IS will transform slower (Sidhu et al, 1980).…”

Section: Colormentioning

confidence: 99%

“…Some authors found that thermal transformation of Fe oxides that were isomorphically substituted caused migration and/or ejection of some elements from the crystalline structure of the mineral (Sidhu et al, 1980;Landers et al, 2009). However, some elements remain in the mineral even after heating (Sidhu et al, 1980 …”

Section: Introductionmentioning

confidence: 99%

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Thermal Transformation and Characterization of Synthetic Al-Substituted Maghemites (γ-Fe2-xAlxO3)

Nonaka

Batista

Inoue

et al. 2016

Rev. Bras. Ciênc. Solo

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ABSTRACT:Burning is a common practice in tropical areas and related changes in mineralogy might affect the chemical and physical behavior of soils. Maghemite is a common iron oxide in soils formed from basic rocks in tropical regions. This mineral and hematite are the main pigments in these soils and exhibit high magnetization stemming from the precursor magnetite formed during the weathering process of primary minerals. The objective of the present study was to analyze changes in color, magnetic suceptibility values, Fourier transform infrared spectroscopy (FTIR) spectra, and available Fe and Al contents extracted with 1 mol L -1 KCl during the process of thermal transformation of synthetic Al-maghemites into Al-hematites. Synthetic substituted maghemites with different degrees of Al-substitution (0.0, 1.0, 2.0, 2.9, 3.8, 5.6, 6.7, 10.0, 12.0, and 17.1 mol% Al) were subjected to a temperature of 500 ± 10 °C for 0, 5, 10, 16, 64, 128, 192, 360, 720, 2160, 3600, 5040 and 6480 min. The color of the samples was analyzed by a Munsell system in a colorimeter. Mass-specific magnetic susceptibility (χ LF ) was measured at low-frequency. Available Fe and Al contents were estimated by a 1 mol L -1 KCl solution. Fourier transform infrared spectroscopy (FTIR) spectra were obtained through use of a Bruker Vertex 70X FTIR spectrophotometer at a spectral resolution of 4 cm -1 . Contents of Fe and Al extracted by 1 mol L -1 KCl in Al-hematites were not detected. All samples analyzed exhibited YR hue. Hue proportion decreased with increased heating time, and color changed from brown to red. The increase in isomorphic substitution (IS) led to increased hue values from maghemite to hematite, and the latter then became yellower. The χ LF values decreased with an increase in heating time, indicating transformation from a ferrimagnetic phase (maghemite) to an antiferrimagnetic phase (hematite). With increasing IS, the maghemite χ LF values decreased. Bands of the initial members (time 0) in the FTIR spectra were indexed as maghemites. The end members after completion of the heat treatment were identified as hematites. The IS of Fe by Al in maghemite influenced the thermal transformation to hematite, as well as the color and χ LF of the minerals. The χ LF proved to be very efficient in detecting maghemites remaining after thermal processing. Fe and/or Al were not ejected from the hematite crystalline structure after heat treatment.

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Section: Available Fe and Al In 1 Mol L -1 Kclcontrasting

confidence: 72%

Section: Colormentioning

confidence: 99%

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Thermal Transformation and Characterization of Synthetic Al-Substituted Maghemites (γ-Fe2-xAlxO3)

Nonaka

Batista

Inoue

et al. 2016

Rev. Bras. Ciênc. Solo

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“…This process is slower in ironsand due to high amount of Ti ). 10,11,13) The XRD patterns of samples heated up to 1 273 and 1 373 K showed that titanium was present in TTM and TTH solid solutions. Ulvospinel (Fe 2 TiO 4 ), ilmenite (FeTiO 3 ) or rutile (TiO 2 ) were not detected.…”

Section: Non-isothermal Oxidationmentioning

confidence: 99%

Effects of Preoxidation of Titania-Ferrous Ore on the Ore Structure and Reduction Behavior

Park

Ostrovski

2004

ISIJ International

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The paper examined an effect of preoxidation of titania-ferrous ore (New Zealand ironsand) on the ore structure and reduction by carbon monoxide.The major phase in ironsand is titanomagnetite, Fe 3 O 4 -Fe 2 TiO 4 solid solution, with spinel cubic structure. In the non-isothermal preoxidation titanomagnetite was oxidized to cubic maghemite and then transformed to rhombohedral titanohematite, Fe 2 O 3 -FeTiO 3 solid solution. Isothermal preoxidation of the ironsand at 1 273 K transformed titanomagnetite to titanohematite and partly to pseudobrookite (Fe 2 TiO 5 ), however, complete oxidation of Fe 2ϩ to Fe 3ϩ in titanomagnetite was not achieved in the experimental condition. The reduction of the titania-ferrous ore was investigated in non-isothermal and isothermal experiments using 75vol%CO-25vol%Ar gas mixtures in a laboratory fixed bed reactor. Samples in the course of reduction were characterized using XRD and EPMA. Preoxidation increased the rate of ironsand reduction.

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“…where [ ] and { } stand for tetrahedral and octahedral sites and L represents cation vacancies in the spinel structure, respectively; in step (2), much of certain substitutional elements (Co, Ni, Zn and Cu) tend to migrate from the lattice toward the surface of the grain whereas Mn and Cr are favourably retained in the hematite structure (Sidhu et al, 1980). Alhematite and Al-goethite are ubiquitously found in pedoenvironments (e.g.…”

Section: Introductionmentioning

confidence: 99%

Magnetita e sua transformação para hematita em um solo derivado de esteatito

Santana

Fabris

Goulart

et al. 2001

Rev. Bras. Ciênc. Solo

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SUMMARYThe main objective of this work was to characterize the magnetic minerals and to identify their pedogenic transformation on a steatite-forming soil of Minas Gerais, Brazil. The iron-rich spinel phase was characterized by chemical analysis, powder X-ray diffraction, Mössbauer spectroscopy, with and without an externally applied magnetic field of 6 tesla, and saturation magnetization measurements. Nearly stoichiometric and well-crystallized magnetite was the only magnetic mineral actually detected. The cubic unit cell parameter of the fresh rock magnetite was found to be a o = 0.8407(5) nm. Hematite (hexagonal cell; a = 0.5036(3) nm, c = 1.375(4) nm) was detected in the altered rock and in the sand-soil and silt-soil fractions. Magnetite is assumed to transform into hematite during pedogenesis through progressive oxidation of structural Fe 2+ to Fe 3+ . In partially oxidized magnetites, a relatively small proportion of Fe 3+ was interpreted as being uncoupled from the Fe 2+ -Fe 3+ charge transfer system, in octahedral sites of the spinel structure. Compositional formulae of magnetite with different degrees of non-stoichiometry are proposed. Ilmenite was found in minor proportions in the magnetically extracted portions from both rock and soil samples.Index terms: Iron-rich spinel, iron oxide, soapstone, magnetic soil, Mössbauer spectroscopy.(1) This work is part of the thesis of the first author, presented to the Departmento

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The Behavior of Co, Ni, Zn, Cu, Mn, and Cr in Magnetite during Alteration to Maghemite and Hematite

Cited by 59 publications

References 0 publications

Thermal Transformation and Characterization of Synthetic Al-Substituted Maghemites (γ-Fe2-xAlxO3)

Thermal Transformation and Characterization of Synthetic Al-Substituted Maghemites (γ-Fe2-xAlxO3)

Effects of Preoxidation of Titania-Ferrous Ore on the Ore Structure and Reduction Behavior

Magnetita e sua transformação para hematita em um solo derivado de esteatito

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