Fe-containing Materials Research Articles

Interfacial geochemistry of iron applied to atmospheric and oceanic environments

Realizing the United Nations Sustainable Development Goals on water and climate through research in chemistry demands innovative and integrated approaches to studying environmental systems from the macro to the molecular scales. Due to the ubiquity of iron (Fe)-containing materials in the natural and built environments, they find their way to air, water, and soil with natural weathering and human activities. These materials are redox and (photo)chemically active with relatively high affinity to complexing inorganic and organic species of relevance to geochemical and atmospheric systems that include outdoor and indoor air. The current state of knowledge of the environmental chemistry of Fe shows that Fe-containing materials influence pollutant transport and transformation, micronutrient availability, and the climate. However, the extent of these influences is affected by the solvation effects of bulk and interfacial water. In this perspectives article, we highlight advances in experimental and theoretical approaches focused on studying the interfacial reactivity of Fe-containing materials in geochemical and atmospheric environments. Specifically, the surface chemistry of Fe-(oxyhydr)oxides and its role in changing the chemical composition of the natural and built environments is presented to connect fundamental concepts to implications. This paper also provides an outlook for future studies in this interdisciplinary area.

Phosphate Removal Mechanisms in Aqueous Solutions by Three Different Fe-Modified Biochars.

Iron-modified biochar can be used as an environmentally friendly adsorbent to remove the phosphate in wastewater because of its low cost. In this study, Fe-containing materials, such as zero-valent iron (ZVI), goethite, and magnetite, were successfully loaded on biochar. The phosphate adsorption mechanisms of the three Fe-modified biochars were studied and compared. Different characterization methods, including scanning electron microscopy/energy-dispersive spectrometry (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), were used to study the physicochemical properties of the biochars. The dosage, adsorption time, pH, ionic strength, solution concentration of phosphate, and regeneration evaluations were carried out. Among the three Fe-modified biochars, biochar modified by goethite (GBC) is more suitable for phosphate removal in acidic conditions, especially when the pH = 2, while biochar modified by ZVI (ZBC) exhibits the fastest adsorption rate. The maximum phosphate adsorption capacities, calculated by the Langmuir-Freundlich isothermal model, are 19.66 mg g-1, 12.33 mg g-1, and 2.88 mg g-1 for ZBC, GBC, and CSBC (biochar modified by magnetite), respectively. However, ZBC has a poor capacity for reuse. The dominant mechanism for ZBC is surface precipitation, while for GBC and CSBC, the major mechanisms are ligand exchange and electrostatic attraction. The results of our study can enhance the understanding of phosphate removal mechanisms by Fe-modified biochar and can contribute to the application of Fe-modified biochar for phosphate removal in water.

Hydrogenation of CO in the Presence of Fe-Containing Materials Based on Carbon Supports

Hydrothermal carbonization of lignin was used to prepare a precursor of a carbon-containing support to obtain supported iron-containing catalysts for the hydrogenation of carbon monoxide. In the paper, the possibility of forming a carbon support prone to the deposition of metal ions was investigated. Deep structural transformations occurring in the polymer matrix of lignin were demonstrated by FTIR spectroscopy. The thermal stability of the support material was determined by thermal analysis in the region up to 400 °C. The formation of magnetite nanoparticles with a size of about 7‒8 nm at the stage of preliminary calcination of the metal-carbon system was shown by X-ray diffraction analysis (XRD). It was found that the resulting systems have high activity comparable to the activity of the system based on activated carbon: the conversion of carbon monoxide reached 98%, the yield of C5+ hydrocarbons reached 72 g/m3.

UV-light-driven conversion of gadoterate meglumine: Insight into the photocatalyst's influence on conversion pathway, transformation products, and release of toxic ionic gadolinium

Dotarem is the most used gadolinium-based contrast agent and one of the main sources of anthropogenic gadolinium in water systems. A Dotarem aqueous solution at its excretion level concentration was photocatalyzed by different materials. A 42% conversion was reached by photolysis, followed by photocatalysis with TiO2, iron oxides, and TiO2/γ-Fe2O3 (39–29%). Transformation products were identified to correspond to hydroxylated-Dotarem derivatives, Gd-free compounds, and Fe-complexes. A conversion pathway was proposed to demonstrate that, under UVC irradiation, Dotarem released toxic Gd3+, and in the presence of Fe-containing materials, transmetallation reactions occurred between the Gd3+ and Fe3+ ions.

Highly Stable Two-Dimensional Iron Monocarbide with Planar Hypercoordinate Moiety and Superior Li-Ion Storage Performance.

Stable planar hypercoordinate motifs have been recently demonstrated in two-dimensional (2D) confinement systems, while perfectly planar hypercoordinate motifs in 2D carbon-transition metal systems are rarely reported. Here, by using comprehensive ab initio computations, we discover two new iron monocarbide (FeC) binary sheets stabilized at 2D confined space, labeled as tetragonal-FeC (t-FeC) and orthorhombic-FeC (o-FeC), which are energetically more favorable compared with the previously reported square and honeycomb lattices. The proposed t-FeC is the global minimum configuration in the 2D space, and each carbon atom is four-coordinated with four ambient iron atoms, considered as the quasi-planar tetragonal lattice. Strikingly, the o-FeC monolayer is an orthorhombic phase with a perfectly planar pentacoordinate carbon moiety and a planar seven-coordinate iron moiety. These monolayers are the first example of a simultaneously pentacoordinate carbon and planar seven-coordinate Fe-containing material. State-of-the-art theoretical calculations confirm that all these monolayers have significantly dynamic, mechanical, and thermal stabilities. Among these two monolayers, the t-FeC monolayer shows a higher theoretical capacity (395 mAh g-1) and can stably adsorb Li up to t-FeCLi4 (1579 mAh g-1). The low migration energy barrier is predicted as small as 0.26 eV for Li, which results in the fast diffusion of Li atoms on this monolayer, making it a promising candidate for lithium-ion battery material.

LiM0.5Mn1.5O4-δ (M = Co or Fe) spinels with a high oxidation state obtained by ultrasound-assisted thermal decomposition of nitrates. Characterization and physicochemical properties

Manganese lithium oxides with spinel-related structure, LiCo0.5Mn1.5O4-δ and LiFe0.5Mn1.5O4-δ, have been synthesized for the first time using an ultrasound-assisted thermal decomposition of nitrates (UA-TDN) synthesis method. The materials were studied by X-ray powder diffraction, scanning and transmission electron microscopy, oxygen stoichiometry determinations, Raman and X-ray photoelectron spectroscopy. The Rietveld refinement of the X-ray diffraction data indicated that the samples crystallize in the Fd3‾m space group which is characteristic of the cubic spinel structure and have a cell parameter of 0.8117 ​nm (LiCo0.5Mn1.5O4-δ) and 0.8254 ​nm (LiFe0.5Mn1.5O4-δ). The Scherrer method and the Williamson-Hall (W–H) method were used to evaluate the crystallite sizes. Energy-dispersive X-ray spectroscopy analyses confirmed that the metals were present in the expected stoichiometry. Scanning and transmission electron microscopy images showed that the particles are of an irregular polyhedral shape, having average sizes of 600 and 750 ​nm for the Co- and Fe-containing materials, respectively. X-ray photoelectron spectroscopy measurements revealed the presence of metal cations in high oxidation states: Co3+, Fe3+, Mn3+ and Mn4+. Considering the ensemble of the results obtained, it is possible to propose the following ionic distributions Li+[Co0.53+Mn0.63+Mn0.94+]O3.952− and Li+[Fe0.53+Mn0.53+Mn1.04+]O42− .

Alterations in Mobility, Survival and Synchrony of Cell Division Close to Biodegradable Iron. Multidimensional Microscopy Analysis Without Use of Stains

The interactions between macrophages and bioabsorbable metals during their degradation may lead to altered functions of these cells. The evaluation of this impact vivo is tricky and the use of cell cultures is a preliminary valuable model. In the Fe-biodegradation case, the system is complex because Fe-containing materials may lead to corrosion products of different composition and solubility. Thus, a meticulous study about interactions between macrophages and Fe-based materials, without using staining to avoid its non-desired effects, is proposed here. Multidimensional microscopy was applied to obtain images of unstained macrophages (J774A.1) exposed to Feo rings. Images were taken every 15 min between 24-48h of exposure. For the first time for this system software tools for single-cell tracking (TrackMate - FIJI) was applied for the analysis of the spatiotemporal dependence of different parameters. As metal degrades, macrophages capture and accumulate the degradation products as a dark insoluble material. Significant changes in macrophage morphology, motility, synchrony of duplications and in survival of cells, according to the distance to the metal, were noticed. They account for the deep impact of Fe-degradation products on the macrophages close to the Fe-containing implant.

Improvement of H2-rich gas production with tar abatement from pine wood conversion over bi-functional Ca2Fe2O5 catalyst: Investigation of inner-looping redox reaction and promoting mechanisms

The objective of this research was to find cost-effective inner-looping redox-reaction-based biomass conversion catalysts by screening five Fe-containing materials through the integration of pine wood pyrolysis and gasification. All the evaluation tests are conducted in a fixed bed reactor under atmospheric pressure. The effect of temperature, water injection rate (steam/biomass ratio), catalyst loading, and reaction time on pine wood conversion performances was investigated. Ca2Fe2O5 catalyst was found to facilitate H2-rich gas production, tar abatement, and carbon conversion. The maximum H2 yield of 7.12 mol·H2/kg·Biomass was obtained in the first 10 min of gasification, which increased H2 yield by 78.98% compared to biomass gasification under the water injection rate of 0.10 mL/min and catalyst load amount of 10 wt.% at 850 °C. Moreover, the hydrogen utilization, carbon conversion, and total gas yield of the process due to the use of Ca2Fe2O5 increase by 13.4%, 17.3%, and 11.7%, respectively. Continuous high yields of H2-enriched syngas were observed during the cyclic stability tests, indicating significant activity and redox durability of Ca2Fe2O5. The catalyst characterization using BET, XRD, H2-TPR, SEM/EDS, and TEM revealed that Ca2Fe2O5 is stable when tested cyclically, which results from the existence of Ca2+ in Ca2Fe2O5. The bi-functional Ca2Fe2O5 catalyst provides a novel way of inner-looping redox reaction for the continuous conversion of biomass.

Origin of Stabilization and Destabilization in Solid-State Redox Reaction of Oxide Ions for Rechargeable Lithium Batteries

Li2MnO3-based materials have been extensively studied as positive electrode materials in the past decade. The reaction mechanism of this material had been the controversial subject for a long time. Since the oxidation state of manganese ions is tetravalent, further oxidation of manganese ions is difficult in Li cells. Instead of manganese ions, negatively charged anions, oxide ions (O2-), donate electrons on charge. However, oxidation of oxide ions results in partial loss of oxygen as an irreversible process, i.e., decomposition reaction. The use of anion redox, especially oxide ions, is a crucial strategy to design and develop new electrode materials with high gravimetric/volumetric energy density for rechargeable lithium batteries. Reversible capacity of electrode materials is potentially further increased by the enrichment of lithium contents with less transition metals in the close-packed structure of oxide ions. Our group has reported that Li3Nb5+O4[1] and Li4Mo6+O5[2], which have higher lithium contents than those of Li2MnO3, are potentially utilized as host structures for a new series of high-capacity electrode materials. Among them, Mn3+-substituted Li3NbO4, Li1.3Nb0.3Mn0.4O2 (0.43Li3NbO4 – 0.57LiMnO2), delivers large reversible capacity (approximately 300 mAh g-1) with highly reversible solid-state redox reaction of oxide ions.[1] Recently, Li2Ti4+O3 is also proposed as the host structure for high-capacity electrode materials with redox reaction of oxide ions.[3] Mn3+-substituted sample, 0.5Li2TiO3 – 0.5LiMnO2 (Li1.2Ti0.4Mn0.4O2), also delivers large reversible capacity as shown in Figure 1a. A voltage profile of Li1.2-x Ti0.4Mn0.4O2 quite resembles that of Li1.3-x Nb0.3Mn0.4O2. Available energy density of Li1.2-x Ti0.4Mn0.4O2 exceeds 1,000 mWh g-1 as a positive electrode material. Moreover, charge compensation is realized by oxidation of oxide ions as evidenced by O K-edge X-ray absorption spectroscopy (Figure 1b) as a reversible process. In contrast to the Mn system, an iron counterpart, xLi2TiO3 – (1 – x) LiFeO2 binary system, shows large polarization on charge/discharge,[4] which is similar to that of Li3NbO4-LiFeO2 binary system.[1] For these Fe-containing materials, oxidation of oxide ions seems to trigger oxygen loss as an irreversible process. From these results, we will discuss the origin of stabilization and destabilization in solid-state redox reaction of oxide ions, and the possibility of high-capacity positive electrode materials, which effectively use the solid-state redox of oxide ions for the charge compensation, consisting of only 3d-transtion metals. Acknowledgements This research has been partly supported by Advanced Low Carbon Technology Research and Development Program of the Japan Science and Technology Agency (JST) Special Priority Research Area “Next-Generation Rechargeable Battery.” References [1] N. Yabuuchi, M. Takeuchi, M. Nakayama, H. Shiiba, M. Ogawa, K. Yamanaka, T. Ohta, D. Endo, T. Ozaki, T. Inamasu, K. Sato, and S. Komaba, Proceedings of the National Academy of Sciences, 112, 7650 (2015). [2] N. Yabuuchi, Y. Tahara, S. Komaba, S. Kitada, and Y. Kajiya, Chemistry of Materials, 28, 416 (2016). [3] N. Yabuuchi et al., submitted [4] S. L. Glazier, J. Li, J. Zhou, T. Bond, and J. R. Dahn, Chemistry of Materials, 27, 7751 (2015). Figure 1

Facile synthetic route towards nanostructured Fe–TiO2(B), used as negative electrode for Li-ion batteries

We present here a novel simple method for the synthesis of highly pure TiO2(B). The fast microwave-assisted synthetic route allows facile scale-up of the process. Aiming at an application of the titania polymorph as negative electrode for Li-ion batteries, we have prepared a Fe-containing TiO2(B) and tested the electrochemical performances of both pure and Fe-containing materials. Fe insertion in TiO2(B) allows enhancing capacity and rate capability.

Effect of Fe content on structural and magnetic properties of SmCo4−xFexB alloys

The phase formation and magnetic behavior of SmCo4−xFexB (x=0, 0.25, 0.5, 0.75, 1 and 2) produced by melt spinning have been investigated. At x=0, melt spinning resulted in the formation of the SmCo4B phase and an ultrahigh coercivity of 44kOe at 300K. Fe substitution resulted in the formation of an amorphous structure along with the Sm(Co,Fe)4B phase during melt spinning. A single Sm(Co,Fe)4B phase was observed after crystallization when x<1, while Sm(Co,Fe)4B and Sm2(Co,Fe)17By were observed when x⩾1. Hysteresis loops at x<1 displayed a single-phase magnetic behavior which was absent when x⩾1. In the crystallized Fe-containing materials, an increase in both coercivity and magnetization with increasing Fe content was observed until x=1. Initial magnetization curves revealed nucleation-controlled behavior at x<1 and a combination of nucleation and domain wall pinning at x=1 and x=2. The average grain size for the annealed SmCo4−xFexB samples measured from TEM micrographs was 110nm for both x=0.5 and x=1 and 90nm for x=2.

Effect of iron content on selectivity in isomerization of α-pinene oxide to campholenic aldehyde over Fe-MMM-2 and Fe-VSB-5

Isomerization of α-pinene oxide to campholenic aldehyde (CA) was investigated over Fe-containing mesoporous mesophase materials (Fe-MMM-2) and microporous nickel phosphate molecular sieves (Fe-VSB-5). Activity and selectivity of reaction towards CA over Fe-containing materials was found to depend on iron content in materials that affects oligomeric state of Fe and amount of Lewis acid sites. In the presence of Fe-VSB-5 selectivity towards CA increased with increase in iron content in structure, while that decreased in the presence of Fe-MMM-2. This phenomenon is related to change in agglomeration of iron species in Fe-MMM-2 structure. The high selectivity towards CA in the presence of Fe-VSB-5 was suggested to arise from unique structure of these materials, which favours shape selectivity.

Magnetic separation of carbon-encapsulated Fe nanoparticles from thermally-treated wood char

Wood char, a by-product from the fast-pyrolysis process of southern yellow pine wood for bio-oil production, was carbonized with Fe nanoparticles (FeNPs) as a catalyst to prepare carbon-encapsulated Fe nanoparticles. A magnetic separation method was tested to isolate carbon-encapsulated Fe nanoparticles from the carbonized char. X-ray diffraction pattern clearly shows that Fe-containing materials were completely separated from the carbonized wood char mixture using a magnet. The amorphous carbon in the material which adhered to the magnetic bar was significantly decreased in comparison with the non-adhered material. Carbon graphitic layers encapsulated FeNPs were observed in the adhered material through high-resolution transmission electron microscopy. In addition, many long and tangled-multi-layered graphitic carbon structures grew from the surface of carbon-encapsulated Fe nanoparticles.

Fe-containing nickel phosphate molecular sieves as heterogeneous catalysts for phenol oxidation and hydroxylation with H2O2

Fe-containing nickel phosphate molecular sieves (Fe-VSB-5) were hydrothermally synthesized in weak basic conditions under microwave irradiation and characterized by SEM, XRD, N2-adsorption/desorption, DRS-UV–vis, and FT-IR spectroscopy using PhCN and CDCl3 as probe molecules. The catalytic activity of Fe-VSB-5 was tested for the phenol hydroxylation and wet phenol oxidation with H2O2. The increase in iron content in Fe-VSB-5 leds to an increase in the reaction rates. The increases in activity can be explained by the role of the Fe species, which increases the generation of radicals. The Fe-VSB-5 samples were stable against the leaching out of Fe ions. The catalytic activity of Fe-VSB-5 was compared to the catalytic activity of traditional Fe-containing materials.

Study of iron(III) polymer complexes using Moessbauer spectroscopy

Metal complexes were prepared on the basis of polymer ligands with carboxylic and nitrogen-containing functionalities by complexation with iron ions in aqueous solutions of FeCl3·6H2O and FeSO4·2H2O. The degree of introduction of iron ions into the polymer matrices depended on the relative content of the functional groups in the polymers studied such as polyacrylic acid, poly-4-vinylpyridine, and poly(2-N,N-dimethylaminoethyl) methacrylate. The metal content in the polymer complexes was found to vary between 9.0 and 30.0 (for acrylic acid-based copolymers); 0.1 and 5.3 (for copolymers of 4-vinylpyridine), and 19.7 and 34.4 (for poly(2-N,N-dimethylaminoethyl) methacrylate) mg metal ions per gram of polymer carrier, respectively. An attempt was made to evaluate the structure of the Fe-containing polymeric materials by Moessbauer spectroscopy. The parameters of the Moessbauer spectra such as the isomer shift, quadrupole splitting, effective internal magnetic field, and relative weight of the partial components were consequently determined for the complexes studied at different temperatures. The results obtained proved the existence of high-spin Fe3+ ions in oxygen- or nitrogen-containing ligand environment.

Abrasion as a Catalyst Deposition Technique for Carbon Nanotube Growth

Mechanical abrasion of stainless steel (SS) surfaces is demonstrated as an effective technique for the deposition of catalyst to support growth of high density layers of carbon nanotubes (CNTs) in water-assisted catalytic chemical vapor deposition. In all cases of Fe-containing materials abraded on Al(2)O(3) substrates, CNT growth is observed; the 400 series of SS appears to deposit catalyst most efficiently. We demonstrate that this simple abrasion technique enables both micro- and nanoscale accuracy in catalyst patterning as well as large area catalyst deposition for uniform, dense CNT growth. Raman spectroscopy characterization indicates high quality CNTs grown by this approach. This technique provides an inexpensive and simple route for addition of catalyst for Fe-based surface growth of CNTs.

Impact of water saturation level on arsenic and metal mobility in the Fe-amended soil

The impact of water saturation level (oxidizing-reducing environment) on As and metal solubility in chromium, copper, arsenic (CCA)-contaminated soil amended with Fe-containing materials was studied. The soil was mixed with 0.1 and 1 wt% of iron grit (Fe(0)) and 1, 7 and 15 wt% of oxygen scarfing granulate (OSG, a by-product of steel processing). Solubility of As and metals was evaluated by a batch leaching test and analysis of soil pore water. Soil saturation with water greatly increased As solubility in the untreated as well as in the Fe-amended soil. This was related to the reductive dissolution of Fe oxides and increased concentration of As(III) species. Fe amendments showed As reducing capacity under both oxic and anoxic conditions. The cytotoxicity of the soil pore water correlated with the concentration of As(III). The Fe-treatments as well as water saturation of soil were less significant for the solubility of Cu, Cr and Zn than for As. The batch leaching test used for waste characterization substantially underestimated As solubility that could occur under water-saturated (anaerobic) conditions. In the case of soil landfilling, other techniques than Fe-stabilization of As containing soil should be considered.

The effect of Fe addition on the densification of B4C powder by spark plasma sintering

Boron carbide is a low-density ceramic with high hardness and stiffness values that make it a valuable candidate for light armor applications. Fully dense boron carbide is fabricated by hot pressing of fine (<2 µm) powder at a relatively high temperature (2150–2200°C). Fully dense boron carbide can be processed from an initial mixture of 5.5 vol.% Fe and low-cost B4C powder by spark plasma sintering (SPS) at 2000°C. At this temperature, Fe-free boron carbide can be consolidated only to 96% of the theoretical density. The effect of the Fe addition on the densities is even more pronounced at lower processing temperatures and is related to the presence of a liquid phase in the Fe-containing material. The resulting microstructure and mechanical properties of the Fe-containing boron carbide are presented and discussed.

Influence of External Factors on Amorphous and Nanocrystalline Soft Magnetic Alloys Studied by Mössbauer Spectroscopy

In this paper, a review of recent 57Fe Mössbauer spectroscopy (MS) studies of external influence on the properties of amorphous and nanocrystalline Fe- and Co-based alloys is submitted. Different types of alloys (FeCuNbZr, FeCuNbSiB, FeCoCuNbB, CoFeZrB and CoFeSiB) in the form of original amorphous and nanocrystalline ribbons were subjected to different external factors: different annealing atmospheres, mechanical stress (for example influence of ball-milling) and tensile stress. It will be shown that the Mössbauer spectrometry is a suitable tool for such studies because the measured spectral parameters are very sensitive to the changes in the vicinity of the probe 57Fe-nuclei and thus, this technique provides a wide variety of information about structural and magnetic behavior of Fe-containing materials.

Diffraction studies of order–disorder at high pressures and temperatures

Recent developments at synchrotron X-ray beamlines now allow collection of data suitable for structure determination and Rietveld structure refinement at high pressures and temperatures on challenging materials. These include materials, such as dolomite(CaMg(CO3)2) that tends to calcine at high temperatures, and Fe-containing materials, such as the spinel MgFe2O4, which tend to undergo changes in oxidation state. Careful consideration of encapsulation along with the use of radial collimation produced powder diffraction patterns virtually free of parasitic scattering from the cell in the case of large volume high-pressure experiments. These features have been used to study a number of phase transitions, especially those where superior signal-to-noise discrimination is required to distinguish weak ordering reflections. The structures adopted by dolomite, and CaSO4, anhydrite, were determined from 298 to 1466 K at high pressures. Using laser-heated diamond-anvil cells to achieve simultaneous high pressure and temperature conditions, we have observed CaSO4 undergo phase transitions to the monazite type and at highest pressure and temperature to crystallize in the barite-type structure. On cooling, the barite structure distorts, from an orthorhombic to a monoclinic lattice, to produce the AgMnO4-type structure.