TG/DTA/MS Study of the thermal decomposition of FeSO4·6H2O

The thermal decomposition of FeSO₄·6H₂O was studied by mass spectroscopy coupled with DTA/TG thermal analysis under inert atmosphere. On the ground of TG measurements, the mechanism of decomposition of FeSO₄·6H₂O is: i) three dehydration steps FeSO₄·6H₂O FeSO₄·4H₂O+2H₂O FeSO₄·4H₂O FeSO₄·H₂O+3H₂O FeSO₄·H₂O FeSO4+H₂O ii) two decomposition steps 6FeSO₄ Fe₂(SO₄)₃+2Fe₂O₃+2SO₂ Fe₂(SO₄)3 Fe₂O₃+3SO₂+3/2O₂ The intermediate compound was identified as Fe₂(SO₄)₃ and the final product as the hematite Fe₂O₃.     

The kinetic parameters of thermal decomposition hydrated iron sulphate

The thermal decomposition of iron sulphate hexahydrate was studied by thermogravimetry at a heating rate of 5°C min^?1 in static air. The kinetic parameters were evaluated using the integral method by applying the Coats and Redfern approximation. The thermal stabilities of the hydrates were found to vary in the order. Fe₂(SO₄)₃·6H₂O → Fe₂(SO₄)₃·4.5H₂O → Fe₂(SO₄)₃·0.5H₂O The dehydration process of hydrated iron sulphate was found to conform to random nucleation mass loss kinetics, and the activation energies of the respective hydrates were 89.82, 105.04 and 172.62 kJ mol^?1, respectively. The decomposition process of anhydrous iron sulphate occurs in the temperature region between 810 and 960 K with activation energies 526.52 kJ mol^?1 for the D3 model or 256.05 kJ mol^?1 for the R3 model.     

Thermal decomposition of Prussian blue under inert atmosphere

The thermal decomposition of Prussian blue (iron(III) hexacyanoferrate) under inert atmosphere of argon was monitored by thermal analysis from room temperature up to 1000?°C. X-ray powder diffraction and ⁵⁷Fe M?ssbauer spectroscopy were the techniques used for phase identification before and after sample heating. The decomposition reaction is based on a successive release of cyanide groups from the Prussian blue structure. Three principal stages were observed including dehydration, change of crystal structure of Prussian blue, and its decomposition. At 400?°C, a monoclinic Prussian blue analogue was identified, while at higher temperatures the formation of various polymorphs of iron carbides was observed, including an orthorhombic Fe₂C. Increase in the temperature above 700?°C induced decomposition of primarily formed Fe₇C₃ and Fe₂C iron carbides into cementite, metallic iron, and graphite. The overall decomposition reaction can be expressed as follows: Fe₄[Fe(CN)₆]₃·4H₂O????4Fe?+?Fe₃C?+?7C?+?5(CN)₂?+?4N₂?+?4H₂O.     

Mechanism and kinetics of inorganic sulphates decomposition

Thermal decomposition of different inorganic sulphates are presented. A number of techniques, but mainly TG and DTA, are used to prove the mechanism and kinetics of CaSO₄, BaSO₄, FeSO₄·xH₂O, Al₂(SO₄)₃·xH₂O under various gas atmospheres. It is shown how the partial pressure of gas components and heating rate may effect the mechanism and kinetic parameters. There are also examples on the effects of some additives and initial treatment on the thermal processes. On the base of the results obtained some recommendations are given concerning the precautions to be taken into account in the thermal decomposition studies and the sulphur recovering.     

Complexation of the Fe(III) and Fe(II) sulphates with diphenyl-4-amine barium sulphonate (DAS) Synthesis,thermogravimetric and spectroscopic studies

Reactions in aqueous-alcoholic solution between diphenyl-4-amine barium sulphonate (Ba-DAS—anionic surfactant) and the hydrated sulphates of Fe(III) and Fe(II) ions and their use to ovtain iron oxides are described here. The formation of Fe(II) complexes was reached by using an excess of Ba-DAS, in absence of light under inert atmosphere. The complexes achieved Fe₂[(C₁₂H₁₀NO₃S)₄]·9H₂O and Fe₃[(C₁₂H₁₀NO₃S)₆]·12H₂O were characterized by TG/DTG and IR, UV-VIS and ⁵⁷Fe-Mössbauer analyses.     

Radiation effects on polymers—X: The grafting of acrylic acid on polyethylene in presence of a redox system using accelerated electrons

Films of low-density polyethylene grafted with various amounts of polyacrylic acid were prepared by the direct irradiation method, using a 10 MeV linear electron accelerator. Aqueous solutions of acrylic acid were used with FeSO₄ · 7H₂O as a redox system. The best graft/homopolymer ratios were obtained at radiation doses between 2 and 3 Mrad, at acrylic acid concentrations of 40–60% and at FeSO₄ · 7H₂O concentrations of 0.25-0.5% by weight. The grafted films were tested for reverse osmosis properties. A membrane with 60% polyacrylic acid content gave 87% salt rejection and a water flux of 0.75 × 10^?5 gm/cm² per sec.     

Preparation of nanocrystalline BiFeO3 and kinetics of thermal process of precursor

The Bi₂Fe₂(C₂O₄)₅·5H₂O was synthesized by solid-state reaction at low heat using Bi(NO₃)₃·5H₂O, FeSO₄·7H₂O, and Na₂C₂O₄ as raw materials. The nanocrystalline BiFeO₃ was obtained by calcining Bi₂Fe₂(C₂O₄)₅·5H₂O at 600 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, FT-IR, X-ray powder diffraction, and vibrating sample magnetometer. The data showed that highly crystallized BiFeO₃ with hexagonal structure [space group R3c(161)] was obtained when the precursor was calcined at 600 °C in air for 1.5 h. The thermal process of the precursor in air experienced five steps which involved, at first, the dehydration of an adsorption water molecule, then dehydration of four crystal water molecules, decomposition of FeC₂O₄ into Fe₂O₃, decomposition of Bi₂(C₂O₄)₃ into Bi₂O₃, and at last, reaction of Bi₂O₃ and Fe₂O₃ into hexagonal BiFeO₃. Based on Starink equation, the values of the activation energies associated with the thermal process of Bi₂Fe₂(C₂O₄)₅·5H₂O were determined. Besides, the most probable mechanism functions and thermodynamic functions (ΔS ^≠, ΔH ^≠, and ΔG ^≠) of thermal processes of Bi₂Fe₂(C₂O₄)₅·5H₂O were also determined.     

Iron(II) sulfate oxidation with oxygen on a Pt/C catalyst: A kinetic study

The kinetics of iron(II) sulfate oxidation with molecular oxygen on the 2% Pt/Sibunit catalyst was studied by a volumetric method at atmospheric pressure, T = 303 K, pH 0.33–2.4, [FeSO₄] = 0.06?0.48 mol/l, and [Fe₂(SO₄)₃] = 0?0.36 mol/l in the absence of diffusion limitations. Relationships were established between the reaction rate and the concentrations of Fe²⁺, Fe³⁺, H⁺, and Cl^? ions in the reaction solution. The kinetic isotope effect caused by the replacement of H₂O with D₂O and of H⁺ with D⁺ was measured. The dependence of Fe²⁺ and Fe³⁺ adsorption on the catalyst pretreatment conditions was studied. A reaction scheme is suggested, which includes oxygen adsorption, the formation of a Fe(II) complex with surface oxygen, and the one-electron reduction of oxygen. The last step can proceed via two pathways, namely, electron transfer with H⁺ addition and hydrogen atom transfer from the coordination sphere of the iron(II) aqua complex. A kinetic equation providing a satisfactory fit to experimental data is set up. Numerical values are determined for the rate constants of the individual steps of the scheme suggested.     

Thermal decomposition mechanism of iron(III) nitrate and characterization of intermediate products by the technique of computerized modeling

The nonahydrate of iron(III) nitrate shows no phase transitions in the range of ?40 to 0 °C. Both hexahydrate Fe(NO₃)₃·6H₂O and nonahydrate Fe(NO₃)₃·9H₂O have practically the same thermal behavior. Thermal decomposition of iron nitrate is a complex process which has a different mechanism than those described for other trivalent elements. Thermolysis begins with the successive condensation of 4 mol of the initial monomer accompanied by the loss of 4 mol of nitric acid. At higher temperature, hydrolytic processes continue with the gradual elimination of nitric acid from resulting tetramer and dimeric iron oxyhydroxide Fe₄O₄(OH)₄ is formed. After complete dehydration, oxyhydroxide is destroyed leaving behind 2 mol of Fe₂O₃. The molecular mechanics method provides a helpful insight into the structural arrangement of intermediate compounds.     

Thermal decomposition of some hexaborates

Thermal decomposition of iron(II) and cobalt(II) hexaborates has been investigated. The methods applied to investigate the process were differential thermal analysis, derivatography, crystallooptics and x-ray study. The following iron(II) hexaborate hydrates, FeO · 3B₂O₃ · 7.5H₂O, FeO · 3B₂O₃ · 5H₂O, FeO · 3B₂O₃ · 0.5H₂O; iron(III) borates, Fe₂O₃ · 6B₂O₃ and 2Fe₂O₃ · B₂O₃; cobalt(II)hexaborate hydrates CoO · 3B₂O₃ · 7.5H₂O, CoO · 3B₂O₃ · 5H₂O, CoO · 3B₂O₃ · 0.5H₂O, CoO · 3B₂O₃ and the decomposition product 2CoO · 3B₂O₃ have been isolated. Hepta- and semihydrates of cobalt(II) and iron(II) hexaborates have been proved to be isomorphous. It has been established that in the case of cobalt and iron hexaborates the exothermic maximum refers to a decomposition reaction and to the formation of a borate containing a smaller proportion of boron and boric anhydride.     

Influence of temperatures and starting materials used to prepare α-Fe2O3 on its catalytic activity at the thermal decomposition of KClO4

In order to elucidate the influence of preparative history of α-Fe₂O₃ on its reactivity, the catalytic thermal decomposition of KClO₄ by α-Fe₂O₃ was studied by means of DTA and X-ray techniques. The catalysts were prepared by the calcination of three iron salts, Fe(OH)(CH₃COO)₂, FeSO₄ ? 7H₂O and Fe₂(SO₄)₃ ? αH₂O, at temperatures of 500–1200°C in air. The lower the preparation temperature of αFe₂O₃, the larger the specific surface area and reversely the smaller the crystalline size. KClO₄ without α-Fe₂O₃ was found to begin fusion and decomposition simultaneously at about 530°C. The addition of αFe₂O₃ resulted in promotion of the decomposition reaction of KClO₄; a lowering of 30–110°C in the initial decomposition temperature and a solid-phase decomposition before fusion of KClO₄. The influence of preparative history of α-Fe₂O₃ on the decomposition mainly depended on the preparation temperature rather than the starting material. The initial decomposition temperature of KClO₄ increased with an increase of the preparation temperature of α-Fe₂O₃. The effect of α-Fe₂O₃ was discussed on the basis of the charge transfer and the oxygen abstraction models.     

Untersuchung von Hydrolysereaktionen zum Aufbau von Eisen(III)‐Oxo‐Aggregaten

Investigation of the Hydrolytic Build‐up of Iron(III)‐Oxo‐Aggregates The synthesis and structures of five new iron/hpdta complexes [{Fe^III₄(μ‐O)(μ‐OH)(hpdta)₂(H₂O)₄}₂Fe^II(H₂O)₄]·21H₂O ( 2 ), (pipH₂)₂[Fe₂(hpdta)₂]·8H₂O ( 4 ), (NH₄)₄[Fe₆(μ‐O)(μ‐OH)₅(hpdta)₃]·20.5H₂O ( 5 ), (pipH₂)_1.5[Fe₄(μ‐O)(μ‐OH)₃(hpdta)₂]·6H₂O ( 7 ), [{Fe₆(μ₃‐O)₂(μ‐OH)₂(hpdta)₂(H₄hpdta)₂}₂]·py·50H₂O ( 9 ) are described and the formation of these is discussed in the context of other previously published hpdta‐complexes (H₅hpdta = 2‐Hydroxypropane‐1, 3‐diamine‐N, N, N′, N′‐tetraacetic acid). Terminal water ligands are important for the successive build‐up of higher nuclearity oxy/hydroxy bridged aggregates as well as for the activation of substrates such as DMA and CO₂. The formation of the compounds under hydrolytic conditions formally results from condensation reactions. The magnetic behaviour can be quantified analogously up to the hexanuclear aggregate 5 . The iron(III) atoms in 1 ‐ 7 are antiferromagnetically coupled giving rise to S = 0 spin ground states. In the dodecanuclear iron(III) aggregate 9 we observe the encapsulation of inorganic ionic fragments by dimeric{M₂hpdta}‐units as we recently reported for Al^III/hpdta‐system.     

Synthesis and Crystal Structures of Bis(1‐{(E)‐2‐pyridinylmethylidene}‐semicarbazone)iron(II) and ‐copper(II) Diperchlorate Monohydrates

The pyridine‐2‐carbaldehyde semicarbazone ligand (HL) reacts with iron(II) and copper(II) perchlorates in boiling ethanol to yield red‐violet [Fe^II(HL)₂](ClO₄)₂·H₂O ( 1 ) and light‐green crystals [Cu^II(HL)₂](ClO₄)₂·H₂O ( 2 ). The crystals are triclinic with the metal ions in an octahedral environment, coordinated to two nitrogen and one oxygen‐donor atom from HL. Electronic, magnetic and electrochemical properties are presented as well.     

Thermal decomposition of synthetic hydrotalcites reevesite and pyroaurite

A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of synthetic hydrotalcites reevesite (Ni₆Fe₂(CO₃)(OH)₁₆·4H₂O) and pyroaurite (Mg₆Fe₂(SO₄,CO₃)(OH)₁₆·4H₂O) and the cationic mixtures of the two minerals. XRD patterns show the hydrotalcites are layered structures with interspacing distances of around 8.0. Å. A linear relationship is observed for the d(001) spacing as Ni is replaced by Mg in the progression from reevesite to pyroaurite. The significance of this result means the interlayer spacing in these hydrotalcites is cation dependent. High resolution thermal analysis shows the decomposition takes place in 3 steps. A mechanism for the thermal decomposition is proposed based upon the loss of water, hydroxyl units, oxygen and carbon dioxide.     

A new high-spin iron(III) bis(aqua) complex with the <Emphasis Type="Italic">meso</Emphasis>-tetra(para-chlorophenyl)porphyrin: X-ray crystallography,Hirshfeld surface analysis,magnetic, EPR and electrochemical properties

Chemical preparation of the bis(aqua) iron(III) metalloporphyrin [Fe^III(TClPP)(H₂O)₂](SO₃CF₃)·2(Pnz)·3/4(C₆H₁₂)·2H₂O (TClPP?=?TClPP?=?5,10,15,20-tetra(para-chlorophenyl)porphyrinato and Pnz?=?phenazine) coordination complex (I) was made. The crystal structure of (I) was determined by X-ray single-crystal diffraction and elucidated by Hirshfeld surface approach. Magnetic, spectroscopic and electrochemical properties were also reported and discussed. The mean equatorial distance (Fe–Np) between the iron(III) atom and porphyrin nitrogen atoms is appropriate to a high-spin (S?=?5/2) iron(III) complex. The high-spin state is also confirmed by both magnetic and electron paramagnetic resonance (EPR) spectroscopy data. The repetitive building unit of the crystal structure provides [Fe^III(TClPP)(H₂O)₂]⁺ ion complexes, two non-coordinated Pnz molecules and two water molecules which are interconnected by O–H···O/N/Cl, C–H···O/F/Cl hydrogen bonds, and by C–X···π, C–H···π and π–π stacking intermolecular contacts, forming a 3D supramolecular network. The role and nature of these intermolecular interactions were quantitatively analysed by 3D Hirshfeld surface analysis and associated 2D fingerprint plots. Cyclic voltammetry measurements indicate a one-electron reversible reduction wave with an E_1/2 (Fe(III)/Fe(II) half-potential value of ?0.24 V, which confirms the high-spin S?=?5/2 state of the studied complex.     

2‐Amino‐5‐(2‐pyridyl)‐thiadiazole as Bidentate Ligand

The amino substituted bidentate chelating ligand 2‐amino‐5‐(2‐pyridyl)‐1,3,4‐thiadiazole (H₂ L ) was used to prepare 3:1‐type coordination compounds of iron(II), cobalt(II) and nickel(II). In the iron(II) perchlorate complex [Fe^II(H₂ L )₃](ClO₄)₂·0.6MeOH·0.9H₂O a 1:1 mixture of mer and fac isomers is present whereas [Fe^II(H₂ L )₃](BF₄)₂·MeOH·H₂O, [Co^II(H₂ L )₃](ClO₄)₂·2H₂O and [Ni^II(H₂ L )₃](ClO₄)₂·MeOH·H₂O feature merely mer derivatives. Moessbauer spectroscopy and variable temperature magnetic measurements revealed the [Fe^II(H₂ L )₃]²⁺ complex core to exist in the low‐spin state, whereas the [Co^II(H₂ L )₃]²⁺ complex core resides in its high‐spin state, even at very low temperatures.     

The study of thermal decomposition kinetics of zinc oxide formation from zinc oxalate dihydrate

This study is devoted to the thermal decomposition of ZnC₂O₄·2H₂O, which was synthesized by solid-state reaction using C₂H₂O₄·2H₂O and Zn(CH₃COO)₂·2H₂O as raw materials. The initial samples and the final solid thermal decomposition products were characterized by Fourier transform infrared and X-ray diffraction. The particle size of the products was observed by transmission electron microscopy. The thermal decomposition behavior was investigated by thermogravimetry, derivative thermogravimetric and differential thermal analysis. Experimental results show that the thermal decomposition reaction includes two stages: dehydration and decomposition, with nanostructured ZnO as the final solid product. The Ozawa integral method along with Coats–Redfern integral method was used to determine the kinetic model and kinetic parameters of the second thermal decomposition stage of ZnC₂O₄·2H₂O. After calculation and comparison, the decomposition conforms to the nucleation and growth model and the physical interpretation is summarized. The activation energy and the kinetic mechanism function are determined to be 119.7 kJ mol^?1 and G(α) = ?ln(1 – α)^1/2, respectively.     

Water-soluble double potassium and ammonium salts of iron(III) and manganese(II) with (hydroxyethylidene)diphosphonic acid

A method to multifold increase the water solubility of diiron(III) tris[(hydroxyethylidene)-diphosphonate) tetrahydrate Fe₂(H₂L)₃·4H₂O and manganese(II) (hydroxyethylidene)diphosphonate dihydrate MnH₂L·2H₂O, prepared by the reaction of 1-hydroxyethylidene-1,1-diphosphonic acid with iron(III)hydroxide and basic manganese carbonate. The method involves conversion of the phosphonates into their double salts Fe₂K₆L₃·4H₂O [Fe₂(NH₄)₆L₃·4H₂O] and MnK_1.3H_0.7L·2H₂O [Mn(NH₄)₂L·2H₂O] by treatment of their aqueous suspensions with potassium or ammonium hydroxides. The solubility of the iron salt increases from 0.2 to 4.0 g per 100 mL solution (20 times) and that of the manganese salt increases from 0.1 to 4.8 g per 100 mL solution (45 times).     

Zur Kenntnis der Sulfite und Sulfithydrate des Eisens und Nickels Röntgenographische,thermoanalytische, IR- und Raman-spektroskopische Untersuchungen

In den Systemen FeSO₃? H₂O und NiSO₃? H₂O konnten folgende Hydrate erhalten werden: α-FeSO₃ · 3H₂O, γ-FeSO₃ · 3H₂O, FeSO₃ · 2,5 H₂O, FeSO₃ · 2 H₂O, NiSO₃ · 6 H₂O, NiSO₃ · 3 H₂O, NiSO₃ · 2,5 H₂O und NiSO₃ · 2 H₂O. Die Gitterdaten der folgenden Hydrate wurden anhand von Einkristallmessungen bestimmt: γ-FeSO₃ · 3 H₂O: a = 965,9(1), b = 557,1(1), c = 944,7(1) pm, Z = 4, FeSO₃ · 2 H₂O (P2₁/n): a = 645,6(1), b = 863,1(1), c = 761,2(1) pm, β = 99,84(1)°, Z = 4, NiSO₃ · 3 H₂O: a = 945,0(1), b = 547,2(1), c = 932,5(1) pm, Z = 4, NiSO₃ · 2,5 H₂O (P4₁2₁2): a = b = 935,3(1), c = 1016,6(1) pm, Z = 8, NiSO₃ · 2 H₂O (P2₁/n): a = 631,4(1), b = 851,0(1), c = 744,7(1) pm, β = 98,91(1)°, Z = 4. Die IR- und Raman-Spektren sowie das Ergebnis thermoanalytischer Messungen (DTA, DTG, Röntgenheizaufnahmen) werden mitgeteilt. Die bei Sulfiten und Sulfithydraten zweiwertiger Metalle bisher beobachteten Strukturtypen werden diskutiert. Sulfites and Sulfite Hydrates of Iron and Nickel. X-ray, Thermoanalytical, I.R., and Raman Data In the systems FeSO₃? H₂O and NiSO₃? H₂O the following hydrates have been found: α-FeSO₃ · 3H₂O, γ-FeSO₃ · 3H₂O, FeSO₃ · 2,5 H₂O, FeSO₃ · 2 H₂O, NiSO₃ · 6 H₂O, NiSO₃ · 3 H₂O, NiSO₃ · 2,5 H₂O and NiSO₃ · 2 H₂O. The following crystal data have been determined by single crystal measurements: γ-FeSO₃ · 3 H₂O: a = 965,9(1), b = 557,1(1), c = 944,7(1) pm, Z = 4, FeSO₃ · 2 H₂O (P2₁/n): a = 645,6(1), b = 863,1(1), c = 761,2(1) pm, β = 99,84(1)°, Z = 4, NiSO₃ · 3 H₂O: a = 945,0(1), b = 547,2(1), c = 932,5(1) pm, Z = 4, NiSO₃ · 2,5 H₂O (P4₁2₁2): a = b = 935,3(1), c = 1016,6(1) pm, Z = 8, NiSO₃ · 2 H₂O (P2₁/n): a = 631,4(1), b = 851,0(1), c = 744,7(1) pm, β = 98,91(1)°, Z = 4. IR, Raman, and thermoanalytical (DTA, DTG, high temperature X-ray) data are presented. The structure types found for sulfites and sulfite hydrates of bivalent metals are discussed.     

Preparation of magnetic nanocrystalline Mn0.5Mg0.5Fe2O4 and kinetics of thermal decomposition of precursor

The spinel Mn_0.5Mg_0.5Fe₂O₄ was obtained via calcining Mn_0.5Mg_0.5Fe₂(C₂O₄)₃·5H₂O above 400 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform FT-IR, X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectrometer, and vibrating sample magnetometer. The results showed that Mn_0.5Mg_0.5Fe₂O₄ obtained at 600 °C had a specific saturation magnetization of 46.2 emu g^–1. The thermal decomposition of Mn_0.5Mg_0.5Fe₂(C₂O₄)₃·5H₂O below 450 °C experienced two steps which involved, at first, the dehydration of five water molecules and then decomposition of Mn_0.5Mg_0.5Fe₂(C₂O₄)₃ into spinel Mn_0.5Mg_0.5Fe₂O₄ in air. Based on Starink equation, the values of the activation energies associated with the thermal decomposition of Mn_0.5Mg_0.5Fe₂(C₂O₄)₃·5H₂O were determined.