Distribution Of Iron Ions Research Articles

Spatial confined synthesis of submicron Fe-MoS2 with abundant surface cationic groups and sulfur vacancies for enhanced peroxymonosulfate activation

ABSTRACT The widespread use of emerging refractory organic contaminants poses a significant threat to human health, prompting the need for a cost-effective and efficient removal strategy. While the iron ions/PMS system effectively removes organic pollutants, slow Fe3+ to Fe2+ transformation hampers its efficiency, and the homogeneous distribution of iron ions complicates separation, resulting in secondary sludge pollution. Herein, we developed a novel submicron Fe-MoS2 (S-Fe-MoS2) catalyst with abundant surface cationic groups and sulfur vacancy through a cationic polyacrylamide aerogels (CPAMA) confined hydrothermal synthesis strategy. These features promote active site exposure, enhance reactant adsorption, and accelerate electron transfer between Mo and Fe sites, improving catalytic kinetics and promoting Fe3+/Fe2+ cycle for PMS activation. As a result, the S-Fe-MoS2/PMS system exhibited a high catalytic rate constant (k obs) of 0.32 min−1, in the degradation of 4-chlorophenol (4-CP), 1.5 times higher than that of the conventional Fe-MoS2/PMS system. It also achieved 82.9% total organic carbon (TOC) degradation within 60 min. Additionally, it possessed similar degradation performance for various organic pollutants, along with remarkable reusability (four cycles) and broad pH adaptability (2–8), indicating significant potential for widespread application. This study provided a new way for developing advanced heterogeneous catalysts with high efficiency for water treatment.

Study of iron ion distribution in rare earth (La, Pr, Sm, Dy) doped nickel-zinc spinel ferrites through Mössbauer spectroscopy

Ni0.5Zn0.5Fe1.95RE0.05O4 (RE=La, Pr, Sm, Dy) spinel ferrites were prepared using the sol-gel method. X-ray diffraction analyses revealed that doping with rare earth ions increases the lattice parameters of the ferrites, accompanied by a decreasing trend due to lanthanide contraction. Mössbauer spectrum showed that rare earth ion doping facilitates the migration of iron ions from B sites to A sites, with the extent of migration increasing alongside the atomic number of the rare earth elements. Vibrating sample magnetometer tests indicated a general decrease in saturation magnetization following rare earth ion doping. A comprehensive investigation into the effects of different rare earth ion dopings on the properties of Ni-Zn ferrites was conducted by calculating theoretical magnetic moments and comparing them with the experimentally measured values. This comparison elucidated the mechanism behind the magnetic alterations in rare earth-doped spinel ferrites, providing theoretical support for future magnetic modulation in these materials.

Unveiling the enhancement mechanism of Fe ion for muscovite flotation: Adjustment of surface potential and agent dispersion

Metal ions have been used to improve the flotation recovery of muscovite, while the enhancement mechanism is still unclear. In this paper, density functional theory (DFT) calculations and molecular dynamics (MD) simulations were employed to investigate the adsorption structure of sodium oleate (NaOL) on muscovite surface, and the diffusivity and foaming of NaOL in the pulp system, in presence of Fe3+ at different pH range. DFT calculation results suggested that the adsorption of iron ions, include FeOH2+ and Fe(OH)2+, could change the surface charge from negative to positive, thus enhancing binding performance for OL−. Moreover, MD simulations indicated that the distribution of iron ions in aqueous solution can significantly affect the dispersion of sodium oleate molecules. Specifically, FeOH2+ may lead to the complexation of oleate ions and result in the agglomeration, which is not conducive to its dispersion in solution. However, Fe(OH)2+ can significantly inhibit the aggregation of OL− molecules, and accelerate the dispersion of OL− in flotation pulp. This work reveals atomic-level mechanism of Fe ion on the dispersion and adsorption of sodium oleate in pulp, which is helpful to the understanding of minerals flotation behavior in presence of metal ions.

Anomalies in the magnetic properties of bismuth-substituted diluted yttrium iron garnet

The magnetic properties and Mössbauer spectra of the Y1.8Bi1.2Fe3.5Ga1.5O12 compound were investigated. A linear temperature dependence of the saturation magnetization, hysteresis, and stability of the coercive field in the magnetically ordered state were found. Using the Mössbauer measurements, the distribution of iron ions over octahedral and tetrahedral sites and the concentration of paramagnetic iron ions were determined. Two critical temperatures – the sublattice magnetization compensation temperature and the ferrimagnet–paramagnet transition temperature – were established. The disappear of the phonon mode in the vicinity of the magnetic transition was observed. The experimental data have been interpreted in terms of the spin–lattice interaction model.

KINETIC MODEL OF THE INITIAL STAGE OF THE PROCESS OF COLLOID RETENTION BY THE PORE SPACE OF SOKYRNITE

The physicochemical phenomena occurring on the surface of sokyrnite grains in complex system "medium grain surface - dispersion medium - surface of suspended particles" have been studied. The framework structure of the sokyrnite structure (rough surface, presence of pores and channels, entrance windows) enables it to work as a "molecular sieve" and to be a highly efficient sorbent-ion exchanger. The porosity of the filter media was determined. Namely: the porosity of the media grains (also called the internal porosity) and the porosity of the intergranular space (media layer). The internal surface area, which is an important quality parameter for sokyrnite as a physical adsorbent, was determined. Several other properties associated with sokyrnite and retained colloidal particles, which affect the strength of the physical adsorption, were investigated. The relationships characterizing the parameters of the zeolite filter media layer were formulated and given. In these studies, the requirements for determining the filter charging time and the optimal technological and design parameters of the filter, according to the operating conditions at a specific water treatment facility, were considered. They determined the need for more detailed research and development of a kinetic model for the initial stage of filtering an aqueous suspension through a filter containing zeolite media. A differential material balance expression for the zeolite filter was formulated. Based on the developed kinetic model, comparative experiments on iron removal from underground natural waters using the above-mentioned filter material were planned and carried out. The mechanism of the distribution of iron ions in the filter space due to the phenomenon of diffusion, in accordance with Fick's first law, is given. The mechanism of iron flake retention by the zeolite media pore space, the consolidation of which occurs during the transition of iron from a divalent to trivalent form, is described. The factors that interfere with autocatalytic processes in iron sediments were described. The dynamics of changes in the concentration of iron in the filtrate after the end of the ion-exchange resource of sokyrnite were studied.

Analysis of the Effect of Applied Load on Crevice Corrosion Behavior

A two-dimensional numerical model incorporating solid mechanics, electrochemistry, mass diffusion, and ion migration processes is developed to investigate the load effect on the crevice corrosion. The model is a transient model of crevice corrosion occurring in cracks of 304 stainless steel in a dilute NaCl solution, and the interaction between stress and electrochemical corrosion was considered. By solving the multiphysical coupling model in COMSOL, the effect of applied load on electrochemical corrosion in the crack tip region was calculated, and the local corrosion current density in the crack tip region with stress concentration within the crack was also calculated by using the Tafel relationship. The distribution of Fe2+ ion, Na+ ion, CL− ion, and H and O2 substance concentrations within the crack cavity is predicted by the equation analysis of substance transport. The results show that metal oxidation is more clearly affected by plastic deformation, the rate of hydrogen evolution reaction increases with stress enhancement, and the oxygen absorption reaction is not affected by stress strain. The distribution of iron ions, hydrogen, and oxygen within the crack is affected by the electrochemical reaction rate, and the distribution of iron ions, sodium ions, and chloride ions is affected by the electrolyte potential.

Detailed composition of iron ions in interplanetary coronal mass ejections based on a multipopulation approach

Context. Coronal mass ejections (CMEs) are extremely dynamical, large-scale events in which plasma – but not only the coronal plasma – is ejected into interplanetary space. If a CME is detected in situ by a spacecraft located in the interplanetary medium, it is then called an interplanetary coronal mass ejection (ICME). This solar activity has been studied widely since coronagraphs were first flown into space in the early 1970s. Aims. Charge states of heavy ions reflect important information about the coronal temperature profile due to the freeze-in effect and it is estimated that iron ions freeze in at heights of ∼5 solar radii. However, the measured charge-state distribution of iron ions cannot be composed of only one single group of plasma. To identify the different populations of iron charge-state composition of ICMEs and determine their sources, we developed a model that independently uses two, three, and four populations of iron ions to fit the measured charge-state distribution in ICMEs detected by the Advanced Composition Explorer (ACE) at 1 AU. Methods. Three parameters are used to identify a certain population, namely freeze-in temperature, relative abundance, and kappa value (κ), which together describe the potential non-Maxwellian kappa distributions of coronal electrons. Our method chooses the reduced chi-squared to describe the goodness of fit of the model to the observations. The parameters of our model are optimized with the covariance-matrix-adaptation evolution strategy (CMA-ES). Results. Two major types of ICMEs are identified according to the existence of hot material, and both, that is, the cool type and the hot type, have two main subtypes. Different populations in those types have their own features related to freeze-in temperature and κ. The electron velocity distribution function usually contains a significant hot tail in typical coronal material and hot material, while the Maxwellian distribution appears more frequently in mid-temperature material. Our model is also suitable for all types of solar wind and the existence of hot populations as well as the change of temperatures of individual populations may indicate boundaries between ICMEs and individual solar wind streams.

Impact of Silica-Modification and Oxidation on the Crystal Structure of Magnetite Nanoparticles

At present, the widespread use of iron oxide nanoparticles, including for commercial purposes, requires strict preservation of their phase composition during their application. The choice of nanoparticle modifier and modification conditions is decisive due to their high sensitivity to oxygen in the case of using real conditions (O2, pH change, etc.). In this work, we studied the change in the phase composition of magnetite nanoparticles after modification with 3-aminopropyltriethoxysilane (APTES) and oxidation with nitric acid in order to estimate the protective potential of the silica shell. After modification by APTES and oxidation with nitric acid, the nonstoichiometric nature of the magnetite nanoparticles according to XRD data increased, which indicates an increase in transition forms compared to the initial sample (magnetite content decreased to 27% and 24%, respectively). In contrast, Mössbauer spectroscopy data detected a decrease in the nonstoichiometric index due to APTES modification conditions, but strong oxidation after exposure to nitric acid. It also showed that by analyzing the data of the diffraction analysis and Mössbauer spectroscopy for the same sample, one can obtain information not only about the ionic composition of “magnetite”, but also about the distribution of iron ions of different charges over the crystalline and amorphous parts of the preparation.

Facile Synthesis and Characterization of Pure Tochilinite‐like Materials from Nanoparticulate FeS

AbstractIn this work, three different tochilinite‐like materials have been obtained by sophisticated synthetic methods that allow to control the distribution of iron ions. The purity of the samples was confirmed by powder X‐ray diffraction. From elemental analysis and Mössbauer spectroscopy data, detailed compositions could be determined: T1) Fe0.76S*0.86 [Fe2+0.01Fe3+0.56Mg2+0.43(OH)2.01]; T2) Fe0.89S*0.85 [Fe2+0.55Fe3+0.11Al3+0.33(OH)1.84(O)0.16]; T3) Fe0.71S*0.79 [Fe2+0.25Fe3+0.73Mg2+0.01Al3+0.01(OH)1.98(O)0.02]. These compositions fit to typical compositions of tochilinite in regard of the amount of iron vacancies and the volume ratio of the hydroxide layers to the sulfide layers. Besides hydroxide ions, oxide ions are also present in the hydroxide layers as a result of surface oxidation after the synthesis due to the high reactivity of the particles. TEM and SEM investigations show that the obtained powders consist mainly of thin sheets accompanied by nanotubes with BET surface areas ranging between 20 m2/g and 40 m2/g. The thermal stability was investigated by TGA and DSC analysis and it depends significantly on the composition.

Importance of Locations of Iron Ions to Elicit Cytotoxicity Induced by a Fenton-Type Reaction.

Simple SummaryThe Fenton reaction generates the hydroxyl radical (•OH), which is the most reactive and toxic reactive oxygen species and widely recognized as a key player in oxidative stress. To clarify whether this highly reactive molecule travels to its biological target, the effects of the site of the Fenton reaction on cytotoxicity were investigated. Cytotoxicity induced by the Fenton reaction was affected by the distribution of iron ions surrounding and/or being incorporated into cells. Cytotoxicity was enhanced when the Fenton reaction occurred inside cells. Instead of enhancing cytotoxicity, extracellular iron ions exerted protective effects against the cytotoxicity of extracellular hydrogen peroxide in an ion concentration-dependent manner. Distance had a negative impact on the reactivity of extracellular •OH and biologically effective targets. Furthermore, an assessment of plasmid DNA breakage showed that the Fenton reaction system did not effectively induce DNA breakage.The impact of the site of the Fenton reaction, i.e., hydroxyl radical (•OH) generation, on cytotoxicity was investigated by estimating cell lethality in rat thymocytes. Cells were incubated with ferrous sulfate (FeSO4) and hydrogen peroxide (H2O2), or pre-incubated with FeSO4 and then H2O2 was added after medium was replaced to remove iron ions or after the medium was not replaced. Cell lethality in rat thymocytes was estimated by measuring cell sizes using flow cytometry. High extracellular concentrations of FeSO4 exerted protective effects against H2O2-induced cell death instead of enhancing cell lethality. The pre-incubation of cells with FeSO4 enhanced cell lethality induced by H2O2, whereas a pre-incubation with a high concentration of FeSO4 exerted protective effects. FeSO4 distributed extracellularly or on the surface of cells neutralized H2O2 outside cells. Cytotoxicity was only enhanced when the Fenton reaction, i.e., the generation of •OH, occurred inside cells. An assessment of plasmid DNA breakage showed that •OH induced by the Fenton reaction system did not break DNA. Therefore, the main target of intracellularly generated •OH does not appear to be DNA.

Magneto-optical properties of nanoparticle dispersions based on Fe-=SUB=-3-=/SUB=-O-=SUB=-4-=/SUB=-, obtained by pulse laser ablation in a liquid

The structure, optical and magneto-optical properties of colloidal solutions of iron oxide nanoparticles obtained by pulsed ablation in distilled water, both without additives and with various functional additives: gold-hydrochloric acid, silicon oxide, and polyvinylpyrrolidone, have been studied. It is shown that the main magnetic phase is magnetite Fe3O4. The size distribution of nanoparticles and the degree of their agglomeration depend on the additives. In the absence of the latter, a very wide of size distributions and strong agglomeration of particles are observed. The narrowest distribution curve with a maximum corresponding to ~7 nm and an almost complete absence of agglomeration are observed for particles synthesized in the presence of polyvinylpyrrolidone. The shape of the spectral dependence of magnetic circular dichroism, which generally corresponds to the spectrum of magnetite, undergoes some modifications for various additives, which is associated with defects in the distribution of iron ions between different positions in the crystal. Keywords: pulsed laser ablation, nanoparticles, colloidal solutions, magnetite, magnetic circular dichroism.

Estimation of iron ion distribution at various sites contributing to saturation magnetization in barium hexaferrite at different sintering temperatures

Barium hexaferrite with generic formula BaFe12O19 was synthesized using sol-gel method by sintering at four different temperatures viz., 950 ∘C, 1050∘C, 1150∘C and 1250∘C. X-ray analysis confirm single phase and from the Rietveld refinement, it has been found that c/a ratio decreases with increase in sintering temperature. An increase in grain size with sintering temperature is evidenced from FESEM morphology. Coercivity declined with increase in sintering temperature and is found to be inversely proportional to grain size. Saturation magnetization of the sintered samples was estimated from hysteresis loops, which show an increase up to 1150∘C and then decrease with further rise in sintering temperature. Decrease of saturation magnetization at 1250∘C is attributed to relocation of Fe3+ ions towards spin down sites. Fe3+ ion distribution contributing to magnetic moment was estimated theoretically using Néel sublattice model with least possible error and was verified using Rietveld refinement analysis.

Магнитооптические свойства дисперсий наночастиц на основе Fe-=SUB=-3-=/SUB=-O-=SUB=-4-=/SUB=-, полученных методом импульсной лазерной абляции в жидкости

The structure, optical and magneto-optical properties of colloidal solutions of iron oxide nanoparticles obtained by pulsed ablation in distilled water, both without additives and with various functional additives: gold-hydrochloric acid, silicon oxide, and polyvinylpyrrolidone, have been studied. It is shown that the main magnetic phase is magnetite Fe3O4. The size distribution of nanoparticles and the degree of their agglomeration depend on the additives. In the absence of the latter, a very wide of size distributions and strong agglomeration of particles are observed. The narrowest distribution curve with a maximum corresponding to ~ 7 nm and an almost complete absence of agglomeration are observed for particles synthesized in the presence of polyvinylpyrrolidone. The shape of the spectral dependence of magnetic circular dichroism, which generally corresponds to the spectrum of magnetite, undergoes some modifications for various additives, which is associated with defects in the distribution of iron ions between different positions in the crystal.

Long- and Short-Range Magnetic Order in Titanomagnetite

Abstract—It is shown that the method of random exchange-interaction fields is suitable for identifying the temperature interval where the short-range magnetic order is still present while the long-range order is already absent. On this interval, the state of the magnetic system is a set of ferromagnetic clusters whose magnetic moment can vary with time and ensure magnetic viscosity. In the paper, the Curie point and paramagnetic Curie point are determined for a two-sublattice ferrimagnetic with the distribution of iron ions corresponding to titanomagnetite.

Study by Mössbauer-Spectroscopy of Iron Oxides in Acid-Resistant Ceramic Materials Based on Production Waste

The distribution of iron ions during firing of acid-resistant ceramic materials based on production waste is established using the Mossbauer effect. It is revealed that in samples containing an increased amount of iron oxide (17 – 18%) strength and frost resistance are better than in specimens containing 6 – 7 % Fe2O3. Calculation of the areas of the doublets of the spectrum showed that iron compounds at the surface of the samples studied (where an oxidizing atmosphere predominates) are mainly represented by hematite, and in their central part (reducing atmosphere) by magnetite, and in this case specimen acid resistance is reduced.

A study of defect structures in Fe-alloyed ZnO: Morphology, magnetism, and hyperfine interactions

In order to study the effect of Fe cation substitution on the local structure, defect formation, and hyperfine interactions in ZnO, Mössbauer spectroscopy measurements of the microwave processed Zn1−xFexO (x=0.05, 0.10, 0.15, and 0.20) nanoparticles, together with ab initio calculations, were performed. Complementary information on the distribution of particle size and morphology, as well as magnetic properties, were obtained by X-ray diffraction, transmission electron microscopy, and squid-magnetometry. The selected model for analyzing the Mössbauer spectra of our samples is a distribution of quadrupole splittings. The fitting model with two Lorentz doublets was rejected due to its failure to include larger doublets. The Fe3+ ions do not yield magnetic ordering in the samples at room temperature. The results from first-principles calculations confirm that the major component of the Mössbauer spectra corresponds to the Fe-alloyed ZnO with Zn vacancy in the next nearest neighbor environment. The magnetic measurements are consistent with the description of the distribution of iron ions over the randomly formed clusters in the ZnO host lattice. While at room temperature all the samples are paramagnetic, magnetic interactions cause a transition into a cluster spin-glass state at low temperatures.

Study of the Distribution of Iron Oxides in Intershale Clay and Oil Sludge Porous Filler with Mossbauer Spectroscopy

A ceramic porous filler obtained from intershale clay and oil sludge, which are pollutants in the environment, is the object of this study. The distribution of iron ions is revealed during the firing of the porous filler with a Mossbauer effect. The transformations of ferrous compounds in redox processes on the surface and in the middle of the samples containing high amount of iron oxide are considered. The experiments showed that the calcined ceramic samples have a zonality: the surface of the samples containing less than 6% of Fe2O3 is lighter than that of the inside part, the surface of the samples containing more than 8% of Fe2O3 is light cherry in color, and the interior part is dark cherry in color. The proposed composition for the production of a porous filler is innovative to decrease the negative impact of toxic wastes on the environment, the novelty of which is protected by a patent of the Russian Federation.

Effect of phase separation on the Jian ware blue colored glaze with iron oxide

This study was aimed to explore the effect of phase separation on the Jian ware blue colored glaze with iron oxide. In order to analyze the forming cause of glaze patterns and their coloring mechanism, the phase, microstructure and chemical state of the samples were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectrum. The results indicated that the addition of calcium phosphate introduced highly-active Ca2+ and P5+ into the glaze. Since Ca2+ with high ionic potential had a greater ability to appeal O2− than Si4+, the glaze melt was separated into calcium-rich phase and silicon-rich phase. The difference of viscosity caused the non-uniform distribution of quartz and glass phase, and then affected the distribution of iron ions in two phases, which formed glaze patterns. Adding P5+ that had a strong effect of reversed polarization on the Fe-O increased the contents of Fe2+ and Fe3+-O-Fe2+, and thus deepened the blue-green of glaze surface. In addition, it promoted the formation of worm-like phase-separated structures and the existence of structural color. Therefore, phase separation enriched not only patterns but also glaze colors of the Jian ware blue colored glaze.

Magnetic Ordering Dependence on Iron Ions Distribution in Cu2FeBO5 Ludwigite

A comparative analysis of the copper and iron ions bonds exchange energies was conducted for various variants of orderings and distributions of iron ions among crystallographic positions in ludwigite Cu2FeBO5. Analysis showed that the exchange bonds of iron ions play a key role in the formation of magnetic order. The magnetic ordering strongly depends on the distribution of iron ions among the positions. In the case when the Fe3+ is in the same position as in Fe3BO5, the most favorable magnetic structure is similar to the magnetic structure of ludwigite Fe3BO5. In other cases, the type of magnetic ordering is different.

Magnetic Interaction between Iron Particles in Lithium Phosphate Systems

The glasses from the system xFe2O3(100 – x)[P2O5 · Li2О] with 0 < x < 50 mol % are studied. These materials have been prepared and characterized by magnetic susceptibility. Iron ions generally modify in different ways the local structure of these glasses, depending on the presence of Li2O in the glass matrix. The results have shown the presence of antiferromagnetic or ferromagnetic interactions between iron ions in the studied glass and temperature range. These data revealed that the valence states and the distribution of iron ions in the glass matrix depend on the Fe2O3 content, and can determine the decreasing of magnetic momentum (μeff).