magnetite hematite oxygen concentration
Mechanism and Kinetics of the Reduction of Hematite to Magnetite …
Oxygen would diffuse from the hematite core to the external border of magnetite, but the mobility of the oxygen anions in the magnetite was negligible in comparison with the ferrous cations . The gaseous reaction product CO 2 migrated back to the gas flow where it could be removed from the fluidized bed reactor [ 11 ].
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The chemistry of hydrothermal magnetite: A review
The minimum oxygen fugacity for any given temperature at which ... The upper limit for magnetite stability is defined by the hematite–magnetite (HM) buffer, beyond which hematite is ... They found that minor and trace element concentrations in magnetite are governed by the successive depletion of lithophile elements in the sulfide …
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Magnetite-hematite transformation: correlation …
Schematic diagram of a magnetite crystal. Surfaces a) 111, b) 100 and 3) 110 are represented by two EBSD maps: phase map and inverse pole figure map.In the phase map, the red area refers to the …
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Mechanism and kinetics of hydrothermal replacement of magnetite by hematite
The replacement of magnetite by hematite was studied through a series of experiments under mild hydrothermal conditions (140-220 ℃, vapour saturated pressures) to quantify the kinetics of the transformation and the relative effects of redox and non-redox processes on the transformation. The results indicate that oxygen is not an essential factor in the …
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Transformation of magnetite to hematite and its influence …
The high fugacity of oxygen in the fluid phase promotes the reaction of Fe 2+ (in solution) with oxygen. ... The transformation of magnetite to hematite during deformation plays an important role in the fabric evolution of the iron formation rocks. The transformation along {111} creates planes of weakness that facilitate fracturing. ...
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Formation of magnetite-(apatite) systems by crystallizing …
Magnetite-(apatite) ore deposits are interpreted as being formed by the crystallization of iron-rich ultrabasic melts, dominantly generated by the interaction of silicate melts with oxidized P-F-SO4-bearing sedimentary rocks. This hypothesis is supported by geologic evidence, experimental studies, numerical modeling, stable and radiogenic …
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Mechanism and Kinetics of the Reduction of …
Abstract. The mechanism and kinetics of the reduction of hematite to magnetite in a laboratory-scale, micro-fluidized bed reactor were isothermally investigated. The procedure consisted of the …
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Kinetics of hematite to magnetite transformation by …
The reduction test also demonstrated a higher reduction rate at 700 °C owing to the reduction of hematite (Fe 2 O 3 ) to magnetite (Fe 3 O 4 ) 33 .
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Mechanism and kinetics of magnetite oxidation under …
A well-characterized sample of commercially-available magnetite with a particle size of approximately 690 nm was oxidized by dissolved oxygen (DO) under alkaline …
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Experimental evidence for non-redox transformations between magnetite
Transformations of magnetite (Fe II Fe 2 III O 4) to hematite (Fe 2 III O 3) (and vice versa) have been thought by many scientists and engineers to require molecular O 2 and/or H 2.Thus, the presence of magnetite and/or hematite in rocks has been linked to a specific oxidation environment. However, the availability of reductants or oxidants in …
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Minerals | Free Full-Text | Dissolution of …
Dissolution mechanisms and kinetics have a key role in better understanding of processes. In this work, magnetite and hematite powder were dissolved in oxalic and nitric acid mixtures at different …
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Hematite vs Magnetite: Identifying Key …
Uses: Hematite is used in the extraction of iron for the manufacture of steel, which is the most popular application of the mineral.The vast quantity of hematite ore mined is then processed into …
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Mineral and Technological Features of …
The magnetite–hematite ores of the Mikhailovskoye deposit are characterized by fine dissemination of ore and gangue minerals, the complexity of the structural and textural features and material …
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Mechanism and kinetics of hydrothermal replacement of …
The reaction mechanism and kinetics of the replacement of magnetite by hematite were investigated by assessing the effect of temperature, solution pH, NaCl …
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Microstructural Changes and Kinetics of Reduction of Hematite …
The microstructures of porous magnetite formed on gaseous reduction of dense hematite have been examined using high-resolution scanning electron microscopy. It has been shown that cellular pores are formed on reduction in the temperature range 573 K to 973 K (300 °C to 700 °C). Dendritic shaped gas pores are formed on reduction at …
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Replacement of magnetite by hematite in hydrothermal …
In this work, high-resolution transmission electron microscopy (TEM) was used to investigate porous hematite from the Baishiya skarn deposit, East Kunlun …
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Replacement of magnetite by hematite in hydrothermal …
The replacement of magnetite by hematite is commonly observed in various geologic systems. In contrast to the formation of hematite by a solid-state oxidation, numerous experimental results have demonstrated that it can also occur by a redox-independent dissolution-reprecipitation reaction. ... When the Si concentration in …
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Experimental evidence for non-redox transformations between magnetite
Most of the previous researchers [5–10] have interpreted the interconversion of these iron oxides as a near-equilibrium redox phenomenon, involving reduction of hematite to magnetite by hydrogen or organic matter, or oxidation of magnetite to hematite by oxygen, such as: 3Fe2 O3 ðHmÞ þ H2 →2Fe3 O4 ðMtÞ þ H2 O ð1Þ 6Fe2 O3 ðHmÞ þ ...
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Review on the Oxidation Behaviors and Kinetics of Magnetite …
Hematite phase is the oxide with the highest oxygen content, followed by magnetite. The ideal stoichiometries of hematite and magnetite are Fe 2 O 3 and Fe 3 O 4, respectively. Theoretically, magnetite is in equilibrium with hematite at low temperature.
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Mechanism and kinetics of magnetite oxidation under …
The magnetite concentration in each specimen was calculated based on the Fe(ii)/Fe ratio obtained from titration, assuming that Fe(ii) ... In this scenario, the diffusion of ferrous ions or oxygen through the hematite is unlikely due to its compact structure, and thus transformation can only occur at the uncovered magnetite surface. ...
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Acidic Dissolution of Magnetite: Experimental Study on …
Magnetite (Fe 3 O 4) is a key economically valuable component in iron ore and is extracted by dissolution processes, but among the Fe (oxyhydr)oxides its solubility behavior is one of the least understood.The objective of this study was to improve understanding of magnetite dissolution mechanisms leading to thermodynamic …
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Reduction of Hematite to Magnetite in CO/CO
In carbon looping combustion technologies, the hematite oxygen carrier material is introduced at the process temperature to the fuel reactor, a fluidised bed reactor, where it is reduced to magnetite under isothermal conditions between 1073 K and 1373 K (800 °C and 1100 °C). ... At a low CO concentration of 2 pct CO, the magnetite is …
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Kinetics of hematite to magnetite transformation by gaseous …
The transformation of weakly magnetic hematite into magnetite can enhance the efficiency of magnetic separation. In this work, chemical reduction of …
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Oxygen isotope fractionation in hematite and magnetite; a …
Yong-Fei Zheng, Klaus Simon; Oxygen isotope fractionation in hematite and magnetite; a theoretical calculation and application to geothermometry of metamorphic iron-formations. European Journal of Mineralogy 1991;; 3 (5): 877–886. doi: . Download citation file: Ris (Zotero) Refmanager; EasyBib; Bookends; Mendeley; …
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Magnetite in the human body: Biogenic vs. anthropogenic
Magnetite is an iron-oxide mineral that occurs naturally on Earth. ... Due to its tendency to react with oxygen to form hematite (Fe 2 O 3) and various iron oxyhydroxides (e.g., ferrihydrite, goethite), magnetite can be used as a powerful tool to explore oxygen concentrations in rocks during geological processes, changes in the …
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Effect of oxygen enrichment on sintering behavior of high …
To achieve high-efficiency utilization of complex and unmanageable iron-containing minerals, the effects of oxygen enrichment on productivity, yield, flame front speed, exhaust gas peak temperature, and desulphurization reaction of the vanadium–titanium magnetite sintering process as well as sinter tumble index and …
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Quantitative determination of magnetite and maghemite in …
Iron oxide nanoparticles are available in two common phases, namely magnetite (Fe3O4) and maghemite (Fe2O3). Upon exposure to oxygen atoms, the magnetite phase readily oxidizes into the maghemite phase with the partial conversion of ferrous ions into ferric ions. We report on the approach to determine the ratio of …
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Chapter 11- Preboiler & Industrial Boiler Corrosion Control
The first and most important is the 0.0002-0.0007 in. (0.2-0.7 mil) thick magnetite formed by the reaction of iron and water in an oxygen-free environment. This magnetite forms a protective barrier against further corrosion. Magnetite forms on boiler system metal surfaces from the following overall reaction:
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Investigation of Magnetite Oxidation Kinetics at the
We investigated the oxidation phenomenon of magnetite concentrate from the Luossavaara-Ki-irunavara Aktiebolag (LKAB) mine in Malmberget, Sweden at the …
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A promising process for transformation of hematite to magnetite …
The hematite conversion is found to be due to the synthesis of magnetite by interaction of Fe(II) and Fe(III) ions in the Bayer liquor, as well as to hematite reduction by ions-reductants from the initial RM; the process of magnetite synthesis is promoted by repeated digestion and enhancement of its duration.
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