Mössbauer and thermogravimetric analysis of the oxidation pathway in the thermal decomposition of FeSO4·7H2O

Bristoti, A.; Kunrath, J. I.; Viccaro, P.J.; Bergter, L.

doi:10.1016/0022-1902(75)80460-x

Cited by 28 publications

(9 citation statements)

References 3 publications

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“…25–30 In a typical procedure, about 1 g of solid metal sulfate polyhydrate was stirred and heated under an argon flow exiting through an external cold trap. Water evolution was monitored and typically ceased after a few minutes at the maximal temperature of: Fe, 140 °C; Zn, 150 °C; Cu, 170 °C; Co, 215 °C, and; Ni, 225 °C.…”

Section: Methodsmentioning

confidence: 99%

“…The divalent transition-metal sulfate monohydrates [M II (SO 4 )(H 2 O)] (M = Fe, Co, Ni, Cu, and Zn) were prepared by dehydration of the heptahydrate or pentahydrate (copper) sulfate, using literature methods. − In a typical procedure, about 1 g of solid metal sulfate polyhydrate was stirred and heated under an argon flow exiting through an external cold trap. Water evolution was monitored and typically ceased after a few minutes at the following maximal temperatures: Fe, 140 °C; Zn, 150 °C; Cu, 170 °C; Co, 215 °C; Ni, 225 °C.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Spin-Polarization-Induced Preedge Transitions in the Sulfur K-Edge XAS Spectra of Open-Shell Transition-Metal Sulfates: Spectroscopic Validation of σ-Bond Electron Transfer

et al. 2017

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Sulfur K-edge XAS spectra of the monodentate sulfate complexes [MII(itao)(SO4)(H2O)0,1] and [Cu(Me6tren)(SO4)] exhibit well-defined pre-edge transitions at 2479.4 eV, 2479.9 eV, 2478.4 eV, and 2477.7 eV, respectively (M = Co, Ni, Cu), despite having no direct metal-sulfur bond, while the XAS pre-edge of [Zn(itao)(SO4)] is featureless. The sulfur K-edge XAS of [Cu(itao)(SO4)] but not of [Cu(Me6tren)(SO4)] uniquely exhibits a weak transition at 2472.1 eV, an extraordinary 8.7 eV below the first inflection of the rising K-edge. Pre-edge transitions also appear in the sulfur K-edge XAS of crystalline [MII(SO4)(H2O)] (M = Fe, Co, Ni, Cu, but not Zn) and in sulfates of higher-valent early transition metals. Ground state density functional theory (DFT) and time-dependent DFT (TDDFT) calculations show that charge transfer from coordinated sulfate to paramagnetic late transition metals produces spin polarization that differentially mixes the spin-up (α) and spin-down (β) spin-orbitals of the sulfate ligand, inducing negative spin density at sulfate sulfur. Ground state DFT calculations show that sulfur 3p character then mixes into metal 4s and 4p valence orbitals and various combinations of ligand anti-bonding orbitals, producing measureable sulfur XAS transitions. TDDFT calculations confirm the presence of XAS pre-edge features 0.5 to 2 eV below the sulfur rising K-edge energy. The 2472.1 eV feature arises when orbitals at lower energy than the frontier occupied orbitals with S 3p character mix with the Cu(II) electron hole. Transmission of spin polarization and thus of radical character through several bonds between the S and the electron hole provides a new mechanism for the counter-intuitive appearance of pre-edge transitions in the XAS spectra of transition metal oxoanion ligands in the absence of any direct metal-absorber bond. The 2472.1 eV transition is evidence for further radicalization from Cu(II), which extends across an H-bond bridge between sulfate and the itao ligand and involves orbitals at energies below the frontier set. This electronic structure feature provides direct spectroscopic confirmation of the through-bond electron transfer mechanism of redox-active metalloproteins.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Spin-Polarization-Induced Preedge Transitions in the Sulfur K-Edge XAS Spectra of Open-Shell Transition-Metal Sulfates: Spectroscopic Validation of σ-Bond Electron Transfer

et al. 2017

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“…In the second and competing scheme, an intermediate basic sulfate (FeOHSO 4 ) is formed by direct oxidation of the monohydrate. In both cases, these intermediates finally decompose to hematite within 550-800°C range [33,[47][48][49][50]. Galwey and Brown summarized a combination of these pathways where ferric sulfate formation was also included [51].…”

Section: Thermal Decomposition Of Iron Sulfatesmentioning

confidence: 99%

Recycling of NdFeB Magnets Using Sulfation, Selective Roasting, and Water Leaching

Önal

Gerven

Guo

et al. 2015

J. Sustain. Metall.

116

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NdFeB magnets currently dominate the magnet market. Supply risks of certain rare earth metals (REMs), e.g., Nd and Dy, demand efficient recycling options that are applicable to different types and compositions with minimum use of chemicals and waste generation. In this study, a hydrometallurgical method is presented, which is adjustable to all NdFeB magnets, regardless of their composition. After completely transforming powdered samples into a sulfate mixture, a suitable selective roasting and water leaching treatment resulted in 95-100 % extraction efficiencies for Nd, Dy, Pr, Gd, Tb, and Eu, while Fe remained in the resultant residue forming a marketable hematitedominated by-product. Impurities other than Fe were also greatly separated from the leachate thereby enabling the production of a liquid with at least 98 % REM purity. Such a solution then can be directly treated with subsequent shortened downstream processes without pretreatments for impurity removal. Due to decomposition reactions of impurities, including Fe, during the selective roasting stage, the majority of consumed acid is recyclable resulting in an environment-friendly flow sheet.

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“…Many researchers studied the mechanism and kinetics of these complex reactions that can be classified into several groups according to the nature of the initial iron-bearing phase. Examples are as follows: the thermal decompositions of iron(III) compounds including FeO(OH), [7][8][9][10][11][12][13][14][15][16][17][18][19][20] Fe 2 (C 2 O 4 ) 3 , [21][22][23] Fe 2 (SO 4 ) 3 , [24][25][26] Fe(OH) 3 , 27 (NH 4 ) 2 Fe-(SO 4 ) 2 , 28 Fe(OH)SO 4 , [29][30][31][32] NaFe(SO 4 ) 2 , Na 3 Fe(SO 4 ) 3 , 33,34 FeCl 3 , 35,36 Fe(OH)CO 3 , 37 and NH 4 Fe(C 2 O 4 ) 2 ; 38 the thermally induced oxidation of metal iron, 39,40 Fe 3 O 4 , 41,42 and iron(II) compounds including FeCl 2 , 43 FeSO 4 , [43][44][45][46][47][48][49][50][51] FeS, 52,…”

Section: Thermal Transformations Of Iron-bearing Materialssclassifica...mentioning

confidence: 99%

Iron(III) Oxides from Thermal ProcessesSynthesis, Structural and Magnetic Properties, Mössbauer Spectroscopy Characterization, and Applications

2002

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Structural and magnetic properties, methods of synthesis, and applications of seven iron-(III) oxide polymorphs, including rare beta, epsilon, amorphous, and high-pressure forms, are reviewed. Thermal transformations resulting in the formation of iron oxides are classified according to different parameters, and their mechanisms are discussed. 57 Fe Mo ¨ssbauer spectroscopy is presented as a powerful tool for the identification, distinction, and characterization of individual polymorphs. The advantages of Mo ¨ssbauer spectroscopy are demonstrated with two examples related to the study of the thermally induced solid-state reactions of Fe 2 (SO 4 ) 3 . Lead-InIron(III) oxide is not only a strategic industrial material but also a convenient compound for the general study of the polymorphism and the mutual polymorphous changes in nanoparticles. The existence of amorphous Fe 2 O 3 and four polymorphs (alpha, beta, gamma, and epsilon) has been established. Their discoveries as well as the majority of formation processes are connected with thermal transformations of iron-bearing materials in an oxidizing atmosphere. 57 Fe Mo ¨ssbauer spectroscopy is a unique method that allows one to distinguish and identify individual structural forms, amorphous and nanostructured Fe 2 O 3 particles, to analyze their magnetic properties and to study their formation mechanism during thermally induced solidstate reactions. In this review, thermal processes resulted in the Fe 2 O 3 formation are classified from different viewpoints and their mechanism is discussed. Applications, structural and magnetic properties, and methods of synthesis of all known forms of iron(III) oxide and their Mo ¨ssbauer characterization are also summarized. A detailed survey of the properties of rare forms (amorphous Fe 2 O 3 , β-Fe 2 O 3 , -Fe 2 O 3 , and highpressure Fe 2 O 3 ) is presented for the first time. With respect to the more known R-Fe 2 O 3 and γ-Fe 2 O 3 , the presented data spring from a series of previous works, including the excellent book by R. M. Cornell and U. Schwertmann. 1 Some unresolved problems, such as the relation between the properties of the original ferrogenous precursor and the structure of the formed iron-(III) oxide, or the experimental possibility to distinguish the amorphous Fe 2 O 3 from nanostructured γ-Fe 2 O 3 or R-Fe 2 O 3 particles are discussed. The value of Mo ¨ssbauer spectroscopy for the characterization of iron(III) oxides produced by thermal processes is demonstrated with two experimental examples taken from our work in the field. † Dedicated to R. L. Mo ¨ssbauer on the occasion of the 40 th jubilee of Nobel Prize presentation.

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Mössbauer and thermogravimetric analysis of the oxidation pathway in the thermal decomposition of FeSO4·7H2O

Cited by 28 publications

References 3 publications

Spin-Polarization-Induced Preedge Transitions in the Sulfur K-Edge XAS Spectra of Open-Shell Transition-Metal Sulfates: Spectroscopic Validation of σ-Bond Electron Transfer

Spin-Polarization-Induced Preedge Transitions in the Sulfur K-Edge XAS Spectra of Open-Shell Transition-Metal Sulfates: Spectroscopic Validation of σ-Bond Electron Transfer

Recycling of NdFeB Magnets Using Sulfation, Selective Roasting, and Water Leaching

Iron(III) Oxides from Thermal ProcessesSynthesis, Structural and Magnetic Properties, Mössbauer Spectroscopy Characterization, and Applications

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