Nature-inspired synthesis of magnetic non-stoichiometric Fe3O4 nanoparticles by oxidative in situ method in a humic medium

Pankratov, D. А.; Anuchina, M. M.

doi:10.1016/j.matchemphys.2019.04.022

Cited by 22 publications

(9 citation statements)

References 62 publications

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“…It can be seen that the sextet itself corresponds to metallic iron (α-Fe) [83], and its distortion is caused by satellite subspectra of those Fe atoms in the α-Fe 1−x A x alloy, which neighboring 1, 2 or more Fe atoms are substituted by atoms of other metals-A [84,85]. The parameters of these subspectra are analogous to those of the subspectrum 1 (Table 3), with the only different chemical shift and effective magnetic field by n•dδ and −n•dH, respectively, where n is the number of a subspectrum, dδ and dH are the changes of the corresponding parameters.…”

Section: Investigation Of Iron Reduction In the Roasted Samplesmentioning

confidence: 99%

Influence of Sodium Sulfate Addition on Iron Grain Growth during Carbothermic Roasting of Red Mud Samples with Different Basicity

Grudinsky

Zinoveev

Pankratov

et al. 2020

Metals

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Red mud is an iron-containing waste of alumina production with high alkalinity. A promising approach for its recycling is solid-phase carbothermic roasting in the presence of special additives followed by magnetic separation. The crucial factor of the separation of the obtained iron metallic particles from gangue is sufficiently large iron grains. This study focuses on the influence of Na2SO4 addition on iron grain growth during carbothermic roasting of two red mud samples with different (CaO + MgO)/(SiO2 + Al2O3) ratio of 0.46 and 1.21, respectively. Iron phase distribution in the red mud and roasted samples were investigated in detail by Mössbauer spectroscopy method. Based on thermodynamic calculations and results of multifactorial experiments, the optimal conditions for the roasting of the red mud samples with (CaO + MgO)/(SiO2 + Al2O3) ratio of 0.46 and 1.21 were duration of 180 min with the addition of 13.65% Na2SO4 at 1150 °C and 1350 °C followed by magnetic separation that led to 97% and 83.91% of iron recovery, as well as 51.6% and 83.7% of iron grade, respectively. The mechanism of sodium sulfate effect on iron grain growth was proposed. The results pointed out that Na2SO4 addition is unfavorable for the red mud carbothermic roasting compared with other alkaline sulfur-free additives.

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Section: Investigation Of Iron Reduction In the Roasted Samplesmentioning

confidence: 99%

Influence of Sodium Sulfate Addition on Iron Grain Growth during Carbothermic Roasting of Red Mud Samples with Different Basicity

Grudinsky

Zinoveev

Pankratov

et al. 2020

Metals

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“…[ 37 ] Considering that the isomeric shifts of the indicated subspectra vary in the range from 0.45 to 0.57 mm s −1 , one can assume that most of the iron is in oxidation state +3, i.e., the samples contain a nonstoichiometric solution “magnetite–maghemite” Fe 3 O 4–δ . [ 38 ] A high content of oxidized iron also evidenced by the appearance of a sextet in the low‐temperature spectrum of the FeC/S sample with parameters corresponding to maghemite γ‐Fe 2 O 3 (#0, Table 5 , Figure 5 ). [ 36 ] Sextet from this group with the minimum magnitude of magnetic splitting and maximum width of resonance lines (#3, Table 4) describes the relaxation part of the spectrum for small particles of nonstoichiometric iron oxide.…”

Section: Resultsmentioning

confidence: 99%

Unusual Effect of Support Carbonization on the Structure and Performance of Fe/Mgal₂o₄ Fischer–Tropsch Catalyst

et al. 2020

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Carbonization of MgAl2O4 spinel via glucose treatment is applied for preparation of spinel‐supported iron Fischer–Tropsch synthesis (FTS) catalysts. The catalysts are characterized by low‐temperature adsorption of N2, transmission electron microscopy (TEM), Mössbauer spectroscopy, in situ magnitometry, and are tested in high‐temperature FTS conditions. Surface carbonization leads to magnetite formation in the course of catalyst calcining, likely due to reductive function of surface carbon. In contrast, hematite is formed if iron precursor is deposited on pristine spinel. Support carbonization facilitates iron precursor reduction into carbide during catalyst activation step in synthesis gas flow and gives rise to highly dispersed iron nanopartilcles. Comparison of sequential and co‐impregnation approaches for support carbonization reveal that the first is preferable in terms of Hägg carbide formation during catalyst activation. Specific activity of the catalysts in high‐temperature FTS is approximately doubled due to the support carbonization. The carbonization also boosts C5+ selectivity and olefin percentage in the product hydrocarbons, while methane formation is suppressed. Adding potassium to catalyst formulation suppresses iron carbide oxidation and Fe3O4 formation, and promotes conversion of χ‐Fe5C2 into θ‐Fe7C3 in FTS conditions.

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“…The remaining three sextets correspond to iron atoms in different crystallographic positions for nonstoichiometric magnetite of the composition Fe3-δO4 ≡ (Fe 3+ )A(Fe 2+ 1-3δFe 3+ 1+2δ#δ)BO4 [49,50]. By analyzing the areas and isomeric shifts of the subspectra related to iron atoms in different crystallographic sites of magnetite, it is possible to estimate the value of the magnetite nonstoichiometric parameter -δ, using the Equation ( 16) [51]:…”

Section: Mössbauer Analysismentioning

confidence: 99%

High-Iron Bauxite Residue (Red Mud) Valorisation Using Hydrochemical Conversion of Goethite to Magnetite

Shoppert¹,

Valeev²,

Diallo³

et al. 2022

Preprint

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Bauxite residue (BR), also known as red mud, is a by-product of the production of alumina via the Bayer process. Because of the high sodium oxide and other impurities content, this material is not used to obtain iron or other iron-containing products. In this paper, the hydro-chemical conversion of goethite (FeOOH) to magnetite (Fe3O4) in high-iron BR from the Friguia alumina refinery (Guinea) by Fe2+ ions in highly concentrated alkaline media was studied. The simultaneous extraction of Al and Na made it possible to obtain a product containing more than 96% Fe3O4. The results show that the magnetization of Al-goethite and Al-hemetite accelerates the dissolution of the Al from the iron mineral solid matrix and from the desilication product (DSP). After ferrous sulfate (FeSO4·7H2O) was added directly at the FeO:Fe2O3 molar ratio of 1:1 at 120 °C for 150 min in the solution with the 360 g L-1 Na2O concentration, the alumina extraction ratio reached 96.27% for the coarse bauxite residue size fraction (Sands) and 87.06% for fine BR obtained from red mud. The grade of iron (total iron in the form of iron element) in the residue can be increased to 69.55% for Sands and 58.31% for BR. The solid residues obtained after leaching were studied by XRD, XRF, TG-DTA, VSM, Mössbauer spectroscopy and SEM to evaluate the conversion and leaching mechanisms and the recovery ratio of Al from different minerals. The iron-rich residues can be used in the steel industry or as a pigment.

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Nature-inspired synthesis of magnetic non-stoichiometric Fe3O4 nanoparticles by oxidative in situ method in a humic medium

Cited by 22 publications

References 62 publications

Influence of Sodium Sulfate Addition on Iron Grain Growth during Carbothermic Roasting of Red Mud Samples with Different Basicity

Influence of Sodium Sulfate Addition on Iron Grain Growth during Carbothermic Roasting of Red Mud Samples with Different Basicity

Unusual Effect of Support Carbonization on the Structure and Performance of Fe/Mgal₂o₄ Fischer–Tropsch Catalyst

High-Iron Bauxite Residue (Red Mud) Valorisation Using Hydrochemical Conversion of Goethite to Magnetite

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Nature-inspired synthesis of magnetic non-stoichiometric Fe3O4 nanoparticles by oxidative in situ method in a humic medium

Cited by 22 publications

References 62 publications

Influence of Sodium Sulfate Addition on Iron Grain Growth during Carbothermic Roasting of Red Mud Samples with Different Basicity

Influence of Sodium Sulfate Addition on Iron Grain Growth during Carbothermic Roasting of Red Mud Samples with Different Basicity

Unusual Effect of Support Carbonization on the Structure and Performance of Fe/Mgal2o4 Fischer–Tropsch Catalyst

High-Iron Bauxite Residue (Red Mud) Valorisation Using Hydrochemical Conversion of Goethite to Magnetite

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Unusual Effect of Support Carbonization on the Structure and Performance of Fe/Mgal₂o₄ Fischer–Tropsch Catalyst