Fe-containing Compounds Research Articles

Influence of Organic Compounds on Ni, Co, Cu, Cr, and Pb Accumulation by Nodules in Agro-Dark-Humus Podbels (Planosols) in the South of Primorskii Region

The involving of organic compounds in accumulation of Ni, Co, Cu, Cr, and Pb by Fe–Mn nodules in agro-dark-humus podbels (Planosols (Aric)) under different types of long-term agrotechnical impact has been studied in the south of Primorskii region. The profile patterns of the level of SOC content in soils and in nodules indicate the active deposition of organic compounds in nodules in the lower parts of soil profiles in the of fallow and phytomeliorative variants of the experiment. Fulvic acids were noted to predominate in the composition of humus in the nodules in these variants. The long-term application of organic fertilizers contributed to the decrease of SOC incorporation into nodules and to the increase of the part of humic acids in nodules. Nodules were characterized by a high accumulation levels of Co and Pb in all variants of the experiment. Accumulation of Ni, Cr, and Cu was recorded in nodules from particular horizons of studied soils. The intensity of elements accumulation in nodules of different variants of the experiment varied. Accumulation of Ni was controlled by the content of Mn-containing compounds. The most active sorption phases of nodules from soils with a longer period of organic matter transformation (fallow variant and long-term addition of manure variant) were Fe-containing and organic compounds.

A Computational exploration of the electronic, mechanical, and magnetic properties of Co2A1−xBxAl full heusler alloys (A, B = Cr, Mn, and Fe)

An investigation of the structural, mechanical, electronic, magnetic, and thermomagnetic properties of Co2A1−xBxAl full Heusler alloys (where A, B = Cr, Mn, and Fe, and x ranges from 0 to 1.0) has been carried out using density functional theory (DFT) and Monte Carlo simulations. The investigation reveals small variations in lattice parameters and elastic modulus across the different compositions. The band gaps, calculated using modified Becke-Johnson (mBJ) potential, are found to be approximately 1.4 eV for Co2CrAl and Co2MnAl, while a lower band gap of 0.8 eV is observed for Co2FeAl, which also exhibits the highest total magnetic moment of 5 μB. The doped structures display band gaps and magnetic moments that are intermediate to the pure compounds. The Fe-Co exchange interaction is identified as the most robust, significantly contributing to the high Curie temperatures in Fe-containing compounds, reaching up to 1120 K in the Co2FeAl alloy. Furthermore, the study underscores the strategic use of atomic substitution as an effective approach to manipulating key properties of these Heusler alloys. The ability to modulate band gaps, magnetic moments, and Curie temperatures through atomic substitution offers a promising pathway for optimizing these materials for specific technological applications, aligning with the needs of advanced functional devices.

Effect of tool design and pass strategy on defect elimination and uniform, enhanced tensile properties of friction stir processed high-pressure die-cast A380 alloy

This work reports a study of friction stir processing (FSP) using different tool designs and altering the pass strategy for two process parameter combinations to locally modify the microstructure and create a defect-free processing zone. FSP is applied on high-pressure die-cast (HPDC) A380 alloy, which is widely used in the die-casting sector for automotive and aerospace applications. Gas and shrinkage porosity, brittle, needle-shaped Fe-containing β-FeSiAl5 intermetallic compounds, Al dendrites, coarse and acicular silicon particles, and large second-phase particulates diminish the uniformity of tensile properties across the thickness of an HPDC plate. FSP can eliminate porosity, refine microstructure, and improve tensile properties. An FSP tool design and a pass strategy are identified for the best microstructure consolidation and uniform, enhanced tensile properties. This study underscores the importance of tool features such as scroll design and flats on tool pins and multiple pass-orientation strategies to optimize defect-free, refined microstructure and uniform tensile strength and ductility across the processing zones of HPDC Al alloys.

Study on physicochemical characteristics, solidification and utilisation of tannery sludge gasification ash

Gasification is an attractive method for tannery sludge (TS) disposal because of its advantages: volume reduction, stabilisation, harmlessness, and energy recovery. TS reduction ash (AR) and TS oxidation ash (AO), simulated from a downdraft fixed bed gasifier (DFBG) and an updraft fixed bed gasifier (UFBG), were investigated on their physicochemical characteristics, solidification behaviour, and value-added utilisation. Results showed that the main mineral matters in AR and AO consisted of Fe-oxids and Fe–Cr compounds, and the DFBG was more suitable for TS gasification than the UFBG because of the lower content of Cr(Ⅵ) in AR. With the addition of waste glass bottles (WGB), the ash fusion temperatures (AFTs) and leaching concentrations of heavy metals in AR and AO decreased significantly, and the heavy metals in AR and AO were successfully immobilised by the wrapping effect of the molten WGB. Moreover, gasification ash, as an auxiliary material for rock wool, reduced the AFTs and viscosity coefficient of the main chemical compositions in rock wool. With the addition of AR, the occurrence of Fe-containing compounds and the extremely low risk of leaching toxicity of heavy metals were observed. The maximum addition proportion of gasification ash was dependent on the maximum content of Fe2O3 allowed in the raw materials of rock wool, and its addition ratio must be below 15%.

Accelerating cathode material discovery through ab initio random structure searching

The choice of cathode material in Li-ion batteries underpins their overall performance. Discovering new cathode materials is a slow process, and all major commercial cathode materials are still based on those identified in the 1990s. Discovery of materials using high-throughput calculations has attracted great research interest; however, reliance on databases of existing materials begs the question of whether these approaches are applicable for finding truly novel materials. In this work, we demonstrate that ab initio random structure searching (AIRSS), a first-principles structure prediction method that does not rely on any pre-existing data, can locate low energy structures of complex cathode materials efficiently based only on chemical composition. We use AIRSS to explore three Fe-containing polyanion compounds as low-cost cathodes. Using known quaternary LiFePO4 and quinary LiFeSO4F cathodes as examples, we easily reproduce the known polymorphs, in addition to predicting other, hitherto unknown, low energy polymorphs and even finding a new polymorph of LiFeSO4F that is more stable than the known ones. We then explore the phase space for Fe-containing fluoroxalates, predicting a range of redox-active phases that are yet to be experimentally synthesized, demonstrating the suitability of AIRSS as a tool for accelerating the discovery of novel cathode materials.

Catalytic activity of K10 montmorillonite in the chemical vapor deposition of multi-wall carbon nanotubes from methane

The catalytic activity of K10 montmorillonite (K10Mt) as a substrate during the chemical vapor deposition (CVD) of carbon nanotubes (CNT) was investigated. The influence of free iron present in the structure of K10Mt during CNT synthesis was investigated. The synthesis was carried out both on samples containing free iron and after its chemical extraction. The structural and microstructural parameters of the samples were characterized by scanning electron microscopy with X-ray dispersion spectroscopy (SEM/EDS), energy dispersive transmission electron microscopy (TEM/EDS), X-ray fluorescence spectroscopy, X-ray diffraction (XRD), infrared spectroscopy (FTIR), and Raman spectroscopy, and X-ray photoelectron spectroscopy. It was found that K10Mt, before Fe removal, was covered with coarser forms of carbon with rounded shapes characteristic for pyrolytic carbon deposits, while after chemical purification the K10Mt particles were covered with regular forms of CNT. During the CVD process at 850 °C, multi-walled carbon nanotubes about 1 μm in length were formed on the surface of pure K10Mt. Under the conditions of synthesis, the K10-Mt/CNT nanocomposites were formed. After extraction of free iron from K10Mt, the most likely nucleation sites for CNT growth were Mg- and Fe-containing compounds structurally integrated with the K10Mt substrate, such as iron phosphides, magnesia, and magnesium aluminate.

Study on the relationship between the tribological properties and oxidation degree of graphene derivatives in O/W emulsion

Graphene oxide (GO) underwent a single and double-side modification with octadecylamine (ODA) to MGO1 and MGO2 respectively. MGO1 and MGO2 were incorporated into the O/W base emulsion respectively to change the composition of the boundary layer and the oil phase. It was found that the tribological properties of MGO1-emulsion were better than that of MGO2-emulsion. Chemical composition analysis of the worn surfaces suggests that MGO1 nanosheets might adsorb more easily onto the surface and react better with the bearing steel to produce C–N–O–Fe-containing compounds than do MGO2 nanosheets, and that MGO1 nanosheets were more actively involved in the shear process that occurs in the contact area. SEM and nanoindentation indicated that there was a non-uniform softer MGO1-tribofilm on metal substrate.

Variation of trace element accumulation by iron-manganese nodules from Dystric Cambisols with and without contamination

The aim of this study was to characterize the influence of soil contamination on the trace element accumulation in nodules, inter-element relationships inside the nodules, and mobility of trace elements incorporated in nodules. We collected nodules sized 2–4 mm from pollution-free areas and areas significantly contaminated by Pb, Cd, and Zn with Dystric Cambisols on the west coast of the Pacific Ocean and studied them using a combination of advanced analytical methods and noninvasive techniques. The accumulation of trace elements by nodules was accompanied by a decrease of element mobility compared to surrounding soils. Nodules from uncontaminated soils can be highlighted as follows: (1) significant enrichment by Co and moderate enrichment by Ni, Cu, and Pb in the absence of Zn and Cd accumulation; (2) the strong affinities of Co and Cu towards Mn, association of Pb and Ni with both Mn and Fe; and (3) higher levels of Mn accumulation than in the nodules from contaminated soils. The main peculiarities of the nodules from contaminated soils were the increase in accumulation levels of Fe, Pb, Zn, and Cd, with the exception of Co; elements that were bound to Fe predominantly; and an increased trace element mobility compared to the nodules from the uncontaminated field. Nodules of two experimental fields had different composition of iron minerals. Iron-Mn nodules act as barriers that limit the input of elements in soil solution. Increases in the Fe-containing compounds (both pedogenic and anthropogenic origin) in nodules enhanced the trace elements removed from the host-contaminated soils.

Upcycling of Electroplating Sludge to Prepare Erdite-Bearing Nanorods for the Adsorption of Heavy Metals from Electroplating Wastewater Effluent

Electroplating sludge is a hazardous waste produced in plating and metallurgical processes which is commonly disposed of in safety landfills. In this work, electroplating sludge containing 25.6% Fe and 5.5% Co (named S1) and another containing 36.8% Fe and 7.8% Cr (S2) were recycled for the preparation of erdite-bearing particles via a facile hydrothermal route with only the addition of Na2S·9H2O. In the sludges, Fe-containing compounds were weakly crystallized and spontaneously converted to short rod-like erdite particles (SP1) in the presence of Co or long nanorod (SP2) particles with a diameter of 100 nm and length of 0.5–1.5 μm in the presence of Cr. The two products, SP1 and SP2, were applied in electroplating wastewater treatment, in which a small portion of Co in SP1 was released in wastewater, whereas Cr in SP2 was not. Adding 0.3 g/L SP2 resulted in the removal of 99.7% of Zn, 99.4% of Cu, 37.9% of Ni and 53.3% of Co in the electroplating wastewater, with residues at concentrations of 0.007, 0.003, 0.33, 0.09 and 0.002 mg/L, respectively. Thus, the treated electroplating wastewater met the discharge standard for electroplating wastewater in China. These removal efficiencies were higher than those achieved using powdered activated carbon, polyaluminum chloride, polyferric sulfate or pure Na2S·9H2O reagent. With the method, waste electroplating sludge was recycled as nanorod erdite-bearing particles which showed superior efficiency in electroplating wastewater treatment.

Can Density Functional Theory Predict Mössbauer Spectra in Pyrolyzed Fe-N-C Catalysts?

57Fe Mössbauer spectroscopy, based on the recoil-free emission and resonant absorption of γ-rays, allows an easier separation of the signals arising from the different Fe environments. This is in the basis of the growing interest of using 57Mössbauer spectroscopy for identification of Fe-based species present in pyrolyzed Fe-N-C catalysts. Because of their high temperature synthesis, these catalysts often comprise different coordinations of atomically-dispersed Fe ions covalently bound to the nitrogen-doped carbon matrix (FeNxCy moieties), but also metallic iron and iron carbides with long-range order.1-3 In the 57Fe Mössbauer spectra (recorded in the absence of a strong external magnetic field) metallic iron and iron carbides result in sextets (except for the paramagnetic γ-Fe structure, leading to singlet spectral component) while the fingerprint of FeNxCy moieties is a doublet spectral component. Precise interpretation of the doublets (often labeled as D1 and D2) allowing to distinguish between iron coordination geometries, spin- and oxidation state remains however challenging and has so far lacked strong theoretical or experimental reference basis for their unambiguous assignments. D1 doublet has an isomer value ranging from 0.33 to 0.4 mm/s and quadrupole splitting (QS) ranging from 0.7 to 1.2 mm/s, which is usually attributed to Fe-N4 defects with Fe2+ in its low spin state. The assignment of the D2 doublet with isomer shifts ranging from 0.36 to 0.52 mm/s and with quadrupole splitting ranging from 2.4 to 2.7 mm/s is more ambiguous. It is attributed to Fe-N4 defects similar to iron phthalocyanine with Fe2+ in its intermediate spin state or to a Fe-N2+2 defect in which Fe binds to four pyridinic nitrogen atoms from two adjacent nitrogen-doped graphene layers. However, these assignments have been based on experimental records of carbon-supported FeN4 macrocycles, which differ greatly from the case in which the Fe-Nx moieties are integrated into the graphene matrix. It appears, therefore, obvious that theoretical Mössbauer spectra should be highly beneficial to rationally assign the D1 and D2 spectra of Fe-N-C materials. Theoretical studies (mostly obtained with density-functional-theory, DFT, based approaches) of 57Fe Mössbauer spectra, have evidenced that the choice of the exchange-correlation functional and atomic basis sets has a strong impact on the accuracy of QS values, in particular for intermediate and high spin iron complexes. It is therefore necessary to examine for every new class of Fe-containing compounds the variation of QS with the DFT functional and other computational details. Theoretical 57Fe Mössbauer spectra in pyrolyzed Fe-N-C catalysts have not yet been made available, which prompted us toward the present DFT study of the quadrupole splitting energies in Fe-N4 defects that are identified as the active sites in the pyrolyzed Fe-N-C materials. Extensive computations of QS in Fe-N4 models with Fe in various coordinations and with different oxidation/spin states have been carried out. The use of several DFT exchange-correlation functionals and basis sets in cluster and periodic approaches are compared and will be reported. The analysis of the DFT calculated values in comparison with experimental data are used to interpret quadrupole doublets ubiquitous in the Mössbauer spectra of pyrolyzed Fe-N-C catalysts. Acknowledgement: This work is supported by the LabEx CheMISyst ANR-10-LABX-05-01.

Enhanced immobilization of arsenic and cadmium in a paddy soil by combined applications of woody peat and Fe(NO3)3: Possible mechanisms and environmental implications

Organic matter (OM) plays an important role in the mobility of heavy metal(loid)s. Peat containing abundant OM can be used as an organic fertilizer improving physical and chemical properties of soil. Previous studies indicated that the immobilization of heavy metal(loid)s by peat is affected by the presence of metal oxides and/or hydroxides and that Fe-enriched peat is very effective in immobilizing metal(loid)s. Accordingly, we hypothesize that simultaneous application of peat and Fe-containing compounds may pronouncedly immobilize heavy metal(loid)s. In this study, the effects of the combined applications of woody peat and Fe(NO3)3 on As and Cd mobilities and accumulations in rice during the whole growth period were investigated by a pot experiment. The combined applications of woody peat and Fe(NO3)3 significantly decreased As(III) and Cd in porewater due to pH increases induced by applications of Fe(NO3)3, and these decreases were enhanced with increasing Fe(NO3)3. In addition, simultaneous application of peat and Fe(NO3)3 significantly decreased mobile portions of As and Cd but significantly increased their immobile portions. Increasing Fe(NO3)3 increased the amount of As immobilized by poorly crystalline Fe oxides. The formation of Fe plaques and production of poorly crystalline Fe oxides were enhanced by Fe(NO3)3 addition, which also contributed to the immobilization of As and Cd in soil. Overall, the combined applications of woody peat and Fe(NO3)3 provided a strategy for simultaneously immobilizing As and Cd in soils and further alleviating their accumulations from soil to rice plants. In paddy soil, the frequent occurrence of iron redox activity due to the alternating wetting and drying cycles provided favorable conditions for interactions between Fe and OM, and this process and its associated metal(loid) immobilization may be more important than we thought and need further study.

Formation of the Fe-Containing Intermetallic Compounds during Solidification of Al-5Mg-2Si-0.7Mn-1.1Fe Alloy

Iron (Fe) is the most common and the most detrimental impurity element in Al alloys due to the formation of Fe-containing intermetallic compounds (IMCs), which are harmful to mechanical performance of the Al-alloy components. In this paper we investigate the formation of Fe-containing IMCs during solidification of an Al-5Mg-2Si-0.7Mn-1.1Fe alloy under varied solidification conditions. We found that the primary Fe-containing intermetallic compound (P-IMC) in the alloy is the BCC α-Al15(Fe,Mn)3Si2 phase and has a polyhedral morphology with {1 1 0} surface termination. The formation of the P-IMCs can be easily suppressed by increasing the melt superheat and/or cooling rate, suggesting that the nucleation of the α-Al15(Fe,Mn)3Si2 phase is difficult. In addition, we found that the IMCs with a Chinese script morphology is initiated on the {1 0 0} surfaces of the P-IMCs during the binary eutectic reaction with the α-Al phase. Both the binary and ternary eutectic IMCs are also identified as the BCC α-Al15(Fe,Mn)3Si2 phase. Furthermore, we found that the Fe content increases and the Mn content decreases in the Fe-containing intermetallic compounds with the decrease of the formation temperature, although the sum of the Fe and Mn contents in all of the IMCs is constant.

Origin, baseline contents, and vertical distribution of selected trace lithophile elements in soils from nature reserves, Russian Far East

Despite extensive studies, little is known about the natural trace lithophile element contents and the relationship between contents of these elements and soil properties in the natural environment. The objectives of this study are as follows: (i) to quantify the natural baseline total trace lithophile element contents in soils, (ii) to identify the main factors controlling the vertical distribution and accumulation of elements, and (iii) to evaluate the anthropogenic influence on the soils in the territory of reserves. In this work, we collected 42 soil samples from conditionally pollution-free Dystric Cambisols of three large natural reserves on the coast of the Russian Far East. Soil samples were analyzed for total trace lithophile elements (Ga, Rb, Sr, V, Y, and Zr), total oxides of some major elements (Si, Al, Fe, and Mn), pH(KCl), organic C, total H, and clay content. The total contents of elements were determined via energy dispersive X-ray fluorescence spectroscopy. The correlations between soil properties and contents of the trace lithophile elements were analyzed. Estimation of additional inputs of trace lithophile elements from external sources was assessed by using corrected technogenic index (Tg) of the elements. Natural baseline total element contents (mg kg−1) were as follows: Ga (5.77–7.27), Rb (68.72–113.55), Sr (56.14–154.70), V (106.90–168.99), Y (18.02–20.98), and Zr (189.74–249.28). Rubidium and Y in soils from all reserves include additions from external sources. These elements tended to accumulate in the upper parts of the soil profiles. Contents of Rb and Y were dependent largely on organic C content, total H content, and Mn-containing compounds of soil. In the territories with the maximum levels of Tg, we identified increased associations of total soil Ga and Sr with organic C content and Mn-Fe-containing compounds, Zr with Fe-containing compounds. Distribution and accumulation of V were mainly controlled by natural soil-forming factors and were mostly dependent on Al2O3 and SiO2 contents in soils. The levels of trace lithophile element contents in the soils from natural reserves depend on the mixed influence of natural environmental conditions (main soil-forming factors, peculiar geographic area) and additional inputs of elements originating from atmospheric deposition of long-distance transported pollutants. Technogenic index (Tg) indicated progressive contamination of soils from all reserves by Rb and Y, and local contamination of soils by Ga, Sr, and Zr. In our study, V was an uncontaminated element.

Structure Evolution from Layered to Spinel during Synthetic Control and Cycling Process of Fe-Containing Li-Rich Cathode Materials for Lithium-Ion Batteries.

As promising cathode materials for lithium-ion batteries (LIBs), Fe-containing Li-rich compounds of Li1+xFe0.1Ni0.15Mn0.55Oy (0 ≤ x ≤ 0.3 and 1.9 ≤ y ≤ 2.05) have been successfully synthesized by calcining the spherical precursors with appropriate amounts of lithium carbonate. The structures, morphologies, and chemical states of these compounds are characterized to better understand the corresponding electrochemical performances. With an increase of lithium content, Li1+xFe0.1Ni0.15Mn0.55Oy evolves from a complex layered-spinel structure to a layered structure. The lithium content also affects the average size and adhesion of the primary particles. At 0.1 C, sample x = 0.1 shows the highest first charge/discharge specific capacities (338.7 and 254.3 mA h g–1), the highest first Coulombic efficiency (75.1%), the lowest first irreversible capacity loss (84.4 mA h g–1), the highest reversible discharge specific capacity, and good rate capability. Notably, voltage fading can be alleviated through the adjustment of structural features. Such superior electrochemical performances of sample x = 0.1 are ascribed to the hierarchical micro-/nanostructure, the harmonious existence of complex layered-spinel phase, and the low charge-transfer resistance. An integral view of structure evolution from layered to spinel during synthetic control and cycling process is provided to broaden the performance scope of Li–Fe–Ni–Mn–O cathodes for LIBs.

Sustainable Aqueous Synthesis and Electrochemical Insights on High-Voltage Sodium Alluaudite Insertion Materials

Manifold consumption of lithium resources for Li-ion batteries has led to concern over their paucity and high cost. It has triggered global research on alternative sodium-ion batteries due to the abundance, economy, non-toxicity and uniform geographical distribution of Na resources. Driven by economy and sustainability, suites of oxide and polyanionic cathode materials have been reported for sodium-ion batteries. The materials economy can be enhanced by using Fe-containing compounds as Fe is earth-abundant. With this spirit, Barpanda et al discovered alluaudite-type Na2Fe2(SO4)3 showing the highest Fe3+/Fe2+ redox activity (ca. 3.8 V vs. Na) along with good electrochemical capacity (ca. 100 mAh/g), reversibility and rate kinetics. Based on inductive effect principle related to electronegative SO4 2- based system like Na2Fe2(SO4)3 can deliver high redox potential. Nevertheless, synthesis of sulphate class of compounds is little tricky as they are prone to water dissolution and thermal decomposition. Hence, all known reports on this SO4-based compound rule out any possible aqueous synthetic routes (e.g. sol-gel, hydrothermal) due to inherent dissolution of SO4-based compounds in water. Thus, a cumbersome solid-state synthesis is employed involving (a) preparation of anhydrous FeSO4 from commercial FeSO4.7H2O, (b) prolonged mechanical mixing of FeSO4 with Na2SO4 and (c) extended annealing (350 °C, 24 h under Ar). It calls for alternate energy-savvy synthesis protocols. Exploring aqueous solvothermal synthesis as economic and scalable method to produce SO4-based alluaudite cathodes, we have implemented two aqueous syntheses for the first time: (1) spray drying and (2) Pechini method. Solution-assisted synthesis has advantage over solid-state synthesis by reducing the annealing temperature and/or duration, since ionic diffusion is faster in liquid than solid media. The current work will demonstrate (i) various aspects of scalable spray drying and Pechini syntheses to form alluaudite cathode materials, (ii) synchrotron diffraction confirming phase-purity, (iii) energy-savvy attributes by benchmarking the lowest annealing temperature (200 °C) and time (6 h), (iv) discovery of two novel alluaudite phases and (v) the electrochemical performance of resulting alluaudite cathodes. These aqueous routes can work as high-throughput synthesis of SO4-alluaudites as well as their solid-solution phases. Aqueous solvothermal route can be used for rapid screening of alluaudite materials. Using these routes, we have produced various solid-solution Na2(Fe1-xMx)2(SO4)3 (M = Mn, Co, Ni) phases as well as stoichiometrically controlled Na2+2xFe2-x(SO4)3 (x = 0-0.22). We will describe the structure, magnetic properties and electrochemical performance performances of this alluaudite family of compounds correlating their structure with electrochemical performance, Na+ diffusion rate kinetics.

Leaching of arsenic, copper and chromium from thermally treated soil

Thermal treatment, if properly performed, is an effective way of destroying organic compounds in contaminated soil, while impact on co-present inorganic contaminants varies depending on the element. Leaching of trace elements in thermally treated soil can be altered by co-combusting different types of materials. This study aimed at assessing changes in mobility of As, Cr and Cu in thermally treated soil as affected by addition of industrial by-products prior to soil combustion. Contaminated soil was mixed with either waste of gypsum boards, a steel processing residue (Fe3O4), fly ash from wood and coal combustion or a steel abrasive (96.5% Fe0). The mixes and unamended soil were thermally treated at 800 °C and divided into a fine fraction <0.125 mm and a coarse fraction >0.125 mm to simulate particle separation occurring in thermal treatment plants. The impact of the treatment on element behaviour was assessed by a batch leaching test, X-ray absorption spectroscopy and dispersive X-ray spectrometry. The results suggest that thermal treatment is highly unfavourable for As contaminated soils as it increased both the As leaching in the fine particle size fraction and the mass of the fines (up to 92%). Soil amendment with Fe-containing compounds prior to the thermal treatment reduced As leaching to the levels acceptable for hazardous waste landfills, but only in the coarse fraction, which does not justify the usefulness of such treatment. Among the amendments used, gypsum most effectively reduced leaching of Cr and Cu in thermally treated soil and could be recommended for soils that do not contain As. Fly ash was the least effective amendment as it increased leaching of both Cr and As in majority of samples.

Flux Crystal Growth and the Electronic Structure of BaFe12O19 Hexaferrite

The barium hexaferrite, BaFe12O19, microcrystals were obtained by the flux crystal growth method and were characterized by XRD, SEM, and TEM methods. XPS measurements were carried out on a powder sample. The binding energy differences between the O 1s and cation core levels, ΔBa = BE(O 1s) – BE(Ba 3d5/2) and ΔFe = BE(O 1s) – BE(Fe 2p3/2), were used to characterize the valence electron transfer on the formation of Ba–O and Fe–O bonds. The chemical bonding effects were considered on the basis of our XPS results measured for BaFe12O19 and the earlier published structural and XPS data for other Ba- or Fe-containing oxide compounds. The band structure of BaFe12O19 was calculated by spin-polarized DFT methods and compared to the valence band spectrum measured by the XPS method.

Magnetic and hyperfine properties of Fe2P nanoparticles dispersed in a porous carbon matrix

Structural and magnetic properties of nanocomposite, consisting of Fe2P particles dispersed in a porous carbon matrix, have fully been investigated using X-ray diffraction, Mössbauer and ac and dc magnetization measurements. Besides production of the nanocomposite, using an activated carbon (prepared by chemical activation of a char with H3PO4), impregnation with a Fe3+ salt in aqueous medium and subsequent heat treatments under N2 flow, we found a formation of hexagonal Fe2−xP and orthorhombic FeP in a mass ratio of 4:1, respectively. Low temperature Mössbauer spectra revealed that a large fraction (ca. 28%) of the material is in the paramagnetic state, suggesting that part of the Fe2−xP phase appears in the form of very small particles. A metamagnetic phase transition was also observed for non-stoichiometric Fe2−xP nanoparticles. It is observed at about 150K, well below the ordering temperature of the Fe2P phase (230K), and is dependent on the dc-probe fields. Also, the Fe2−xP nanoparticles were found to have a hard-like magnetic character at low temperatures, with coercive field HC of 1.3KOe. Considering these interesting magnetic and hyperfine properties and also the large specific surface area of the porous carbon matrix, which is not severely reduced after impregnation with the Fe-containing compounds, one may point to promising technological applications of the produced nanocomposite.

Microstructure and mechanical properties of Gd-modified A356 aluminum alloys

The effect of Gd modification on the microstructure and mechanical properties of A356 aluminum alloys was investigated using the metallurgical microscopy, scanning electronic microscopy, X-ray diffraction and mechanical testing. The addition of 0.2 wt.%–0.4 wt.% Gd had an excellent refining effect on primary α-Al grains and a modification effect on Si phases in its as-cast state. The needle-like Si phases were adjusted into fine particles and uniformly distributed in the matrix by the T6 treatment, especially for the 0.2 wt.% Gd-modified alloy. The Gd additions introduced the Fe-containing GdAl2Si2 compounds, which precipitated in the forms of flakes and bulks. The GdAl2Si2 and β-Al5FeSi phases were also refined by the T6 treatment. The mechanical properties of the Gd-modified alloys were very poor in as-cast state; however, the highest strength and elongation were obtained for the 0.2 wt.% Gd-modified alloy by the T6 treatment.

Sewage Treatment Performance of Biological Aerated Filters with Fe-Containing Compound Clinoptilolite Media

Fe-containing compound clinoptilolite media (Fe-M), prepared with natural clinoptilolite, was applied to be the filter media of BAF, and then the treating performance of sewage by BAFs with Fe-M and ceramsite were investigated. Because Fe-M had relatively larger surface area, better pore connectivity, higher biofilm microbial biomass, and the ion-exchanging and adsorption effect, a higher ammonia nitrogen removal efficiency was obtained in BAF with Fe-M than ceramsite; and higher phosphorus removal in BAF with Fe-M was also realized by the adsorption and precipitation effect of the leaching ferric ions. Fe-M is more suitable to be used as the filter of BAF to treat sewage wastewater than ceramsite, which has a high value of broad application prospects and engineering popularization value.