Amount Of Fe3 Research Articles

Effects of Transiotion Metal Co-Doping on the Electrochemical Properties of Li3V2-2xFexMnx(PO4)3/Graphene Cathode Material for Lithium Secondary Battery

A series of Fe and Mn co-doped Li3V2–2xFexMnx(PO4)3/graphene (x = 0, 0.005, 0.010, 0.015, 0.020, and 0.025) samples have been fabricated via a sol-gel assisted microwave synthesis method. The crystal structure and morphology of the synthesized Li3V2–2xFexMnx(PO4)3/graphene was investigated using an X-ray diffraction (XRD) and a scanning electron microscopy (SEM) systematically. Electrochemical measurement results prove that the Li3V1.98Fe0.01Mn0.01(PO4)3/graphene sample presents the best electrochemical performance as the cathode material for lithium ion batteries among the as-prepared samples in the potential ranges of 3.0–4.8 V. The resulting Li3V1.98Fe0.01Mn0.01(PO4)3/graphene cathode has an excellent specific capacity of 184.4 mAh g−1 at 0.1C rate, and even at 10C rate, it still delivers the specific capacity of 110.5 mAh g−1. The substitution of V3+ with an appropriate amount of Fe2+ and Mn4+ increases the Li+ diffusion coefficient assuming from the electrochemical impedance spectroscopy results, which is mainly responsible for the excellent electrochemical performance. Figure 1

First crystal-structure determination of chromites from an acapulcoite and ordinary chondrites

AbstractWe report the first crystal-structure determinations of chromites from an acapulcoite and from ordinary chondrites. Cell edges range from 8.3212 (3) to 8.3501 (1) Å, while the oxygen positional parameters are in the range 0.2624 (3) to 0.26298 (9). Their compositions show they are very close to the chromite end-member FeCr2O4 with limited Al and Mg content. Titanium oxide content exceeds 1 wt.%, whereas the amount of Fe3+ is negligible. Extraterrestrial chromite is distinguished readily from terrestrial analogues on the basis of the cell edge and oxygen positional parameter. These distinctions will facilitate ongoing attempts to reconstruct the palaeoflux of meteorites to Earth from resistant extraterrestrial spinel grains recovered from ancient sediments.

Position of Fe ions in MgO crystalline structure

Abstract Magnesium oxide (MgO) is one of the most important raw materials in many branches of industry. Magnesium oxide is a popular refractory raw material because of its high refractoriness and high resistance to basic slags and environment. In many cases, use of MgO is limited by its properties, especially the presence of secondary phases like iron oxides. The amount and distribution of iron oxides can strongly influence the technological properties of MgO and depend on the manufacturing method, particularly the heat-treatment process. The aim of the study was to evaluate the influence of the heat-treatment process on amount and distribution of iron ions in a magnesium oxide lattice. The 57Fe Mössbauer effect measurements of fused and sintered magnesium oxide samples doped by the iron oxide were conducted. Investigation reveals in both cases the presence of Fe2+ as well as Fe3+ ions. Fe2+ ions occupy Mg2+ octahedral sites in the MgO lattice, whereas the Fe3+ ions are located in highly distorted octahedral coordination. The amount of Fe2+ varies from around 66% for fused samples to 30% for sintered samples.

Magnetic property and electronic structure of BaFe4-xTi2+xO11

In this paper, polycrystalline BaFe4-xTi2+xO11 (x=0, 0.25, 0.5, 0.75, 1) samples have been synthesized by the conventional solid-state reaction method. X-ray diffraction (XRD) patterns of all the samples show that the diffraction peaks correspond to that of an R-type hexagonal ferrite structure, and no trace of second phase is detected. Measurement of X-ray photoelectron spectroscopy (XPS) reveals that most of the Fe ions in BaFe4Ti2O11 are trivalent and the fitting of two peaks in Fe 2p spectrum corresponding to different Fe ion sites, while the amount of Fe2+ ions increases with the increase of Ti ions in BaFe4-xTi2+xO11. The spectroscopy of Ti ions confirms that the valence of Ti in BaFe4-xTi2+xO11 are tetravalent. Magnetic susceptibility of BaFe4-xTi2+xO11 (x= 0, 0.25, 0.5, 0.75, 1) reveals two magnetic transitions at T1～250 K and T2～83 K, which indicate a complex magnetic order driven by competing interactions on a frustrated lattice with a noncentrosymmetric structure. For all the samples, the magnetic susceptibility obeys Curie-Weiss law above T1, and M-H curves exhibit a linear variation with magnetic field in this temperature range, which is consistent with the paramagnetic behavior. A decrease of the effective magnetic moment is due to the increase of Fe2+ ions with the increase of Ti content in BaFe4-xTi2+xO11. Below T1, the magnetization curve as a function of temperature (M-T) and the magnetization versus magnetic field (M-H) at different temperatures imply its characteristic of a typical canted antiferromagnetic or ferrimagnetic state. Meanwhile, the transition temperature T2 drops gradually with the increase in Ti content, which might be related to the change of occupying of Fe ions in the kagome layers.

도시하수 처리 혐기성 유동상 반응조의 후속공정으로서 화학응집의 가능성 평가

This study examined a feasibility of coagulation as post-treatment to remove sulfide and phosphorus for the effluent of anaerobic fluidized bed reactor (AFBR) treating domestic wastewater. Removal efficiencies of sulfide, phosphorus and COD by coagulation were not affected by pH in the range of 5.9 to 7.2. Alkalinity requirement could be estimated by the amount of Fe3+ to form Fe(OH)3(S) and to remove sulfide and phosphorus. At coagulant aid dosage of 2 mg/L, anionic polymer showed best results regarding size and settleability of flocs. Sulfide removal for the AFBR effluent at the Fe3+/S2- ratio of 0.64, close to the theoretical value of 0.67 found with a synthetic wastewater, was only 75.2%. One of the reasons for this low sulfide removal is that the AFBR effluent contains, phosphorus, hydroxide and bicarbonate which can react with Fe3+ competitively. Concentrations of sulfide and phosphorous reduced to below 0.1 and 0.5 mg/L, respectively, at the Fe3+/S2- ratio of 2.0. Average effluent COD of 80 mg/L, mostly soluble COD, was obtained at the dosage 50 mg Fe3+/L (Fe3+/S2- ratio of 2.0) with corresponding COD removal of 55%. For better removal of COD, soluble COD removal at the AFBR should be enhanced. Coagulation with Fe3+ removed sulfide, phosphorus and COD simultaneously in the AFBR effluent, and thus could be an alternative process for the conventional wastewater treatment processes where relatively high quality effluent is not required.

Enhanced Solar-Photocatalytic Degradation of Combined Chlorophenols Using Ferric Ions and Hydrogen Peroxide

The influences of ferric ions (Fe3+) and hydrogen peroxide (H2O2) on the degradation of combined chlorophenols during solar/TiO2 process were investigated. 4-Chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) were used as a chlorophenols combined mixture. Fe3+ ions have shown considerable effect on the solar-photocatalytic degradation rate of the mixture and its intermediates. Different amounts of Fe3+ ions were used, and the optimum value was 10 mg/L. At these conditions, three major intermediates were detected including hydroquinone (HQ), phenol (Ph), and 4-chlorocatechol (4-cCat). However, the concentrations of these aromatic intermediates were less than that of using TiO2 alone as well as the degradation time was reduced to 150 min. H2O2 was also effectively used as a degradation enhancer at various concentrations together with Fe3+ ions in order to improve the solar-photocatalytic degradation rate and the optimum value was 3.41 mM. The degradation efficiency of the combined mixture increased sharpl...

Temperature Frequency Characteristics of Charge Transition in the Li0.5Fe2.4Ti0.1O4 Non-stoichiometric System

A study of conductivity temperature frequency dependence of Li0.5Fe2.4Ti0.1O4 non-stoichiometric spinel has exhibited frequency dispersion conductivity presence. The time of relaxation (τ) proved to make 2·10-6s within the limits of dispersion. The conductivity size was found to be dependant upon the amount of Fe2+ ions in the structure.

Influence of Fe2+-sodium persulfate on extracellular polymeric substances and dewaterability of sewage sludge

Activated persulfate generated from Fe2+-sodium persulfate (SPS) was used as a conditioner for dewatering of waste activated sludge. The effects of Fe2+-SPS on dewaterability were investigated by specific resistance to filtration (SRF) and capillary suction time (CST), as well as further confirmed the results with diaphragm filter press dewatering process in laboratory. The amount of extracellular polymeric substances (EPS) and zeta potentials were analyzed. With 30 mg Fe2+ per gram dry solid (DS) and 100 mg SPS per gram DS, 89.0% of SRF and 84.1% of CST reductions were achieved, respectively. Furthermore, the dewatered cake moisture content was as low as 52.6% in the diaphragm filter press dewatering. The EPS fractions and zeta potential of the sludge floc were found to have significantly changed during the Fe2+-SPS conditioning. Proteins and polysaccharides contents in filtrate all increased with increase in the amount of Fe2+-SPS, but decreased in tightly bound EPS (TB-EPS). The change of proteins content in loosely bound EPS (LB-EPS) was more significant than polysaccharides. Scanning electron microscope images further demonstrated that the Fe2+-SPS pre-treatment ruptured the sludge floc resulting in the formation of permeable and incompressibility structure in filtration process.

Synthesis of Fe<sup>3+</sup> Doped Bi<sub>2</sub>MoO<sub>6</sub> Nanoplate and its Performance on Photocatalytic Degradation of Salicylic Acid

Fe3+ doped Bi2MoO6 photocatalyst was successfully synthesized via a hydrothermal process using Bi (NO3)3 and (NH4)6 Mo7O244H2O as starting materials. XRD, SEM and UV-Vis absorption spectrum techniques were employed to characterize the phase composition and spectrum properties of the as-synthesized samples. Salicylic acid was selected as a model pollutant to investigate the effect Fe3+ doping on the photocatalytic activity of as-synthesized Bi2MoO6. The experimental results indicated that Fe3+ element doping can enhance the photocatalytic activity of Bi2MoO6 photocatalyst. When the amount of Fe3+ doped in Bi2MoO6 is 0.5%, the photocatalyst exhibits the best photocatalytica activity. The doped Fe3+ doped into the crystal lattice of Bi2MoO6 photocatalyst act as the electron traps and facilitates the separation of the separation of photogenerated electron-hole pairs due to its electron deficient. Thus, Fe3+ doping improve the photocatalytic with great efficiency.

Modification of montmorillonite with sodium sulfide for prebiotic chemistry studies: Characterization using spectroscopy methods and X-ray diffractometry

Changes in the mineral characteristics of montmorillonite (Mt) resulting from exposure to sodium sulfide (Na2S) or artificial seawater revealed the capacity for clays to absorb and protect amino acids or nucleic acids from hydrolysis or UV radiation on the prebiotic Earth. The pH of isoelectric point (pHiep) of the modified montmorillonite (MMt) increased probably due to the adsorption of Na+ from the solution of Na2S, and would likely enhance the adsorption of biomolecules that are not protonated at higher pH. However, the exchange of cations with Na+ from artificial seawater or Na2S solutions likely contributed to the observed decrease in the interlayer distance of all treated samples. The associated release of Fe3+ from treated Mt likely decreased the capacity for the clay to adsorb biomolecules. The amount of Fe2+ in solution decreased by almost 50% when Mt was mixed with artificial seawater, but this decrease was not observed when Mt exposed to Na2S and artificial seawater. Given the capacity for Fe2+ to react with nucleic acids, this protection could be important for establishing chemical environments on the prebiotic Earth.

Magnetic and Mössbauer Studies of Mn$_{0.679{-}{\rm x}}$Zn$_{0.256}$Ti$_{\rm x}$Fe$_{2.066}$O$_{4}$ Spinel Ferrites: Effect of Cation Distribution

MnZn ferrites substituted with titanium having the compositional formula of Mn0.679-xZn0.258TixFe2.066O4 (x = 0, 0.010, 0.020, 0.030) were prepared via a conventional ceramic process. The effect of titanium concentration on magnetic properties such as permeability, power loss, and Curie temperature were investigated. Moreover, Mossbauer spectra was recorded at room temperature. The cation distribution obtained from analysis of Mossbauer spectra revealed that the substitution of MnZn ferrites by titanium can move part of Fe3+ from octahedral (B) site to tetrahedral (A) site. Remarkably, this resulted in an increase in the amount of Fe2+A-Fe3+B ion pairs and the Curie temperature. The results obtained and mechanisms involved are discussed.

Influence of Oxygen Annealing on Electromagnetic Properties of Low Temperature Fired Ferrite/Ceramic Composite Materials

Ni-Cu-Zn ferrite (NCZF) /BaTiO3 (BT) composites with different mass ratios of BT/NCZF (x) were prepared at 900°C with suitable fluxing agents. The sintered samples were then annealed in oxygen to reduce the amount of Fe2+ ions. Influence of annealing on electromagnetic properties and frequency characteristics of the samples has been investigated. The Snoek product can be somewhat improved by annealing in samples with x=10wt%, 20wt%, and 30wt%. The dielectric properties can be obviously improved in samples with x=10wt% and 30wt% after annealing in O2.

Solid phase extraction of heavy metals on chemically modified silica-gel with 2-(3-silylpropylimino) methyl)-5-bromophenol in food samples

Trace amounts of Fe3+, Pb2+, Cu2+, Ni2+, Co2+ and Zn2+ ions were efficiently enriched following complexation with silica-gel chemically functionalized with 2-((3-silylpropylimino)methyl)-5-bromophenol. The enriched metal ions efficiently eluted with 6 mL of 4.0 mol L−1 nitric acid and their metal contents were determined by flame atomic absorption spectrometry (FAAS). The influences of the analytical parameters and experimental variables on the recoveries of the metal ions under study were investigated and optimized. The method has high sorption preconcentration efficiency even in the presence of various interfering ions. At optimum values of all variables the method is applicable for analysis of real samples with recoveries in the range of 95 to 105% with RSD lower than 4.2% and detection limits between 1.4 and 2.8 µg L−1.

Development of ceramic based on steel slag with different magnesium content

The steel slag based ceramics (SSBC) with different contents of magnesium ions were prepared by conventional sintering process. The variations of linear shrinkage, water absorption, bulk density and apparent porosity of the samples fired at different temperatures from 1130 to 1210°C were measured. The phase formation and microstructure of final ceramics were observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that increasing magnesium ions content in SSBC does not change the crystal phases but increases the sintering temperature. The final phases in SSBC are pyroxenes including augite and diopside. Crystalline phases in SSBC form before densification. Substitution of Fe2+ for Mg2+ in phases would increase amount of Fe2+ in crystal, but decreases the amount in liquid, which is the main factor of the sintering temperature increase. Good degrees of densification and high crystallinity of ceramics show good mechanical properties.

Increase in ferric and ferrous iron in the mouse lung after asbestos exposure

Pulmonary toxicity induced by asbestos is thought to be mediated through redox-cycling of fiber-bound and bioavailable iron (Fe).This impacts an oxidative stress which potentially mediates a cascade of events culminating in inflammation, fibrosis and cancer (Ghio et al, 2008 and 2009). The present study aimed to elucidate in a murine model of asbestos exposure the distribution of ferric and ferrous iron and its relation with the development of fibrosis. C57/Bl/6 mice were exposed to saline or crocidolite asbestos in saline (55 and 110 µg intra-tracheally) and examined at 1 and 6 months for lung pathology. The left lung was embedded in paraffin, sectioned and stained with hematoxylin and eosin (H&E) and Masson’s trichrome. A modified Perl’s or Turnbull’s blue histochemical stain was used to demonstrate Fe3+ and Fe2+ respectively (Wang et al, 2002). One month following exposure, mice instilled with crocidolite displayed a significant inflammatory injury on staining with H&E (relative to animal exposed to saline). Crocidolite fibers could be observed most frequently in the region of distal bronchioles. The retention of these fibers was associated with an accumulation of inflammatory cells, predominantly macrophages. This response persisted 6 months following asbestos instillation. Increased collagen was observed at one and 6 months after asbestos exposure. One important observation made in 1-month H&E-stained slides of asbestos-exposed mice was the presence of focal atypical hyperplastic lesions. These lesions did not progress in severity from 1 to 6 months. Histological lung sections from saline exposed mice did not stain for both ferric and ferrous Fe. However, one month following crocidolite instillation, a number of Fe3+-positive (but no Fe2+-positive) cells (predominantly macrophages) were present, in the lower respiratory tract. At 6 months postinjection, an increase number of Fe3+-positive cells was observed and also some Fe2+ positive cells were present. The observation of some Fe2+ positive cells in the lung of asbestos exposed mice at 6 months postinjection suggests a shift in the oxidation state of the accumulated iron, with more cells becoming Fe2+-positive at a late stage. These growing amounts of Fe2+ could support a continuated generation of oxidative stress resulting in clinical manifestations, which culminate in inflammarory, fibrotic and hyperplastic lesions.

Valence states of iron ions in nanostructured yttrium iron garnet Y3Fe5O12 studied by means of soft X-ray absorption spectroscopy

Nanostructured samples of yttrium iron garnet Y3Fe5O12 obtained by plastic deformation method (high-pressure torsion) were studied with help of soft X-ray absorption spectroscopy using Fe 2p and O 1s spectra. Experimental spectra were compared with crystal field multiplet calculations for Fe ions. Some amount of Fe2+ ions in nanostructured Y3Fe5O12 was found. The concentration of Fe2+ ions was found to be increased with the increase of the degree of plastic deformation.

Methyl-orange and cadmium simultaneous removal using fly ash and photo-Fenton systems

Wastewaters resulting from the textile and dye finishing industries need complex treatment for efficient removal of colour and other compounds existent in the dyeing and rising baths (heavy metals, surfactants, equalizers, etc.). Modified fly ash (FA) mixed with TiO2 photocatalyst represent a viable option for simultaneous removal of dyes and heavy metals, and the optimized conditions are discussed in this paper for synthetic wastewaters containing methyl-orange (MO) and cadmium. For a cost-effective dye removal process, further tests were done, replacing the photocatalyst with a (photo)Fenton system. The optimized technological parameters (contact time, amount of fly ash and amount of Fe2+/H2O2) allow to reach removal efficiencies up to 88% for the heavy metal and up to 70% for the dye. The adsorption mechanisms and the process kinetic are discussed, also considering the possibility of in situ generation of the Fenton system, due to the fly ash composition.

Humic acid characteristics and effects on the reactivity of nano-scale zero-valent iron particles during nitrate reduction

ABSTRACT Humic acid (HA) comprises a significant fraction of natural organic matter (NOM), greatly influencing the performance of water and wastewater treatment processes. HA is expected to significantly affect the reactivity of nano-scale zero-valent iron (NZVI), which is receiving increasing attention due to its high reactivity. The effects of HA on nitrate reduction by NZVI were investigated to evaluate the potential of NZVI in practical applications. HA was characterized to identify the mechanism whereby HA affects. Nitrate reduction was enhanced at low HA concentration, but inhibited as HA concentration increased. HA decreased to reach a plateau and considerable amount of Fe3+ was detected when HA was present in dissolved phase. The increase in the degree of condensation of HA was verified by UV–vis spectroscopy, fluorescence spectroscopy, and size exclusion chromatography. Fourier transform infrared spectra confirmed that the Fe3+–HA complexes were formed in both the dissolved and solid fractions, without coexisting metal ions. The HA aggregation on NZVI and discrete HA macroaggregates were observed by transmission electron microscopy. The results suggest that HA induces complex effects on NZVI reactivity by improving iron dissolution, inhibiting readsorption of released iron, enhancing electron transfer, and inhibiting nitrate mass transfer via forming HA accumulation. It indicates that the clogging by aggregated NOM should be considered when NZVI is used for groundwater treatment or in combination with porous materials.

Thermal Conductivity of the Molten CaO-SiO2-FeO x System

Thermal conductivity measurements were carried out on synthetic steelmaking slag using the hot-wire method. Furthermore, local structure analysis in the melts was carried out in order to investigate the relationship with the composition dependence. The thermal conductivity of the CaO-SiO2-FeO x melts significantly decreased as the content of FeO x increases, particularly at lower basicity. Both chemical analysis and the observation show that the amount of Fe2+ increases when CaO/SiO2 is smaller, implying more basic behavior of FeO than FeO1.5. According to further analyses by Mossbauer spectroscopy, the degree of basicity of FeO1.5 remains virtually unchanged in the composition range of interest. From the experimental results, it could be concluded that the thermal conductivity of the silicate melt containing iron oxide is highly dependent on the valence of the Fe ion and comparatively independent of the amphoteric behavior of FeO1.5.

Investigation of local structure effect and X-ray absorption characteristics (EXAFS) of Fe (Ti) K-edge on photocatalyst properties of SrTi(1−x)FexO(3−δ)

In this study, the STFx photocatalyst powder was synthesized with a high temperature solid state reaction. The microstructures and surface of samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The electronic properties and local structure of the perovskite STFx (0 ≤ x ≤ 1) systems were probed by extended X-ray absorption fine structure (EXAFS) spectroscopy. The XPS results revealed that with increasing iron doping, the amount of Fe3+ and Fe4+ increased significantly. The X-ray absorption data are discussed in detail with respect to the Fe (Ti) K-edge. The substitution of iron by titanium increased the Ti (Fe)–O first shell disorder factors that can be explained by increasing the oxygen vacancies. Oxygen vacancies or defects act as electron traps, which could capture the photo induced electrons and thus could effectively inhibit the recombination of the photo induced electrons and holes. Moreover due to the substitution of Ti with Fe, lattice shrinkage was observed and the largest derivation from the Gaussian distribution in STFx was from those samples with x = 0.6 and x = 0.8. The substitution of iron by titanium increased the iron valence state, hence the formation of the Jahn–Teller Fe4+ ion. With increasing iron dopant the [Ti(Fe)–O]ave decreased and bond length of [Ti–O] and the consequent [Ti–O–Ti] increased and this phenomenon affected the photocatalyst and photo degradation properties of material and also decreased its efficiency.