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Feiite (Fe3TiO5) is a high-pressure Fe-Ti oxide mineral recently discovered in martian meteorite Shergotty. Feiite is isostructural with Fe4O5, a high-pressure iron oxide stable at pressures >10 GPa. The stability of feiite has yet to be studied, as it has not previously been synthesized in the laboratory. To determine the minimum pressure at which feiite can be synthesized, we have conducted multi-anvil experiments at 1200 °C and at pressures ranging from 7 to 12 GPa. Major element compositions and XRD patterns indicate that we successfully synthesized feiite with an orthorhombic unit cell (Cmcm structure) in experiments conducted at pressures 8 GPa or greater. Relative to A2B2O5 phases with similar structure, feiite can be synthesized at lower pressures. The coexistence of feiite and liuite (FeTiO3-perovskite) in Shergotty indicates that the upper pressure limit of feiite stability is above 15 GPa. To investigate the effect of oxygen fugacity on the composition and stability of feiite, we conducted an additional series of experiments at 1200 °C and 10 GPa pressure in which we varied the Fe3+/Fetotal ratio of the experimental starting materials. In doing so, we identified a minimum Fe3+ content necessary to stabilize the feiite structure (Fe3+/Fetotal = 0.26 at 10 GPa and 1200 °C). The importance of Fe3+ for feiite stability suggests this phase would not form in lunar or HED meteorites, where iron-titanium oxides contain little to no ferric iron. Though our experimental results can only place a lower limit on the shock pressures experienced in Shergotty, the determined pressure stability indicates feiite could also be present in diamond-bearing terrestrial rocks sourced from the upper mantle or transition zone. Additionally, the presence of feiite would be an indicator of source Fe3+/ Fetotal. [ABSTRACT FROM AUTHOR]

In order to meet the environmental legislations related to sulfur content, it is important to find an alternative techniques for deep removal of sulfur components from fuels. So, in this study, a novel nano-catalyst based on iron oxide (Fe2O3) as active component prepared over composite support (γ-Alumina + HY-zeolite) is developed here for efficient removal of sulfur compounds from fuel via oxidation process. The precipitation method is employed first to prepare the composite support and then the impregnation method is utilized to generate a novel synthetic homemade (Fe2O3/composite support) nanocatalysts that has not been developed in the literature (iron oxide over composite support). The characterizations of the prepared catalysts display that the surface area of the catalyst increases with increasing the amount of Y-zeolite in composite support. The effectiveness of the catalysts is tested by utilizing oxidative desulfurization (ODS) operation under several operating conditions. The results of the experimental work show that the activity of oxidative desulfurization enhances with increasing Y-zeolite, temperature, and batch time under moderate operating conditions. The oxidative desulfurization efficiency followed the order: CAT-1 < CAT-2 < CAT-3. The CAT-3 performed the high removal of sulfur compounds (90.73%) at 100 min and 423 K. The best values of the kinetic parameters of the ODS process are then determined based on experimental data and model based techniques within gPROMS package. Finally, the reactor model is used to determine the optimal operating conditions while maximizing the removal of sulfur compounds leading to cleaner fuel. Where, 99.3% of the sulfur removal has achieved at batch time of 190.6 min, temperature of 543.56 K and initial sulfur content at 0.8668 wt% in the presence of CAT-3 based on the optimal kinetic parameters (order of reaction (n) of 1.9865719, activation energy (EA) at 29.942 kJ/mol and pre-exponential factor (k0) with 622.926 wt−0.9865719 min−1). [ABSTRACT FROM AUTHOR]

Hybrid nanofluids can provide better physical strength, thermal conductivity, and mechanical resistance in many thermodynamic systems than pure nanofluids. To establish the novel results, using superior types of hybrid nanoparticles like graphene oxide (GO) and iron oxide (Fe3O4) is the main focus of recent work. This study investigates the innovative thermal and magnetic features of both pure nanofluid GO/engine oil (EO) and hybrid nanofluid GO–Fe3O4 /EO under the simultaneous effects of induced as well as applied magnetic field. The chemical reaction phenomenon together with activation energy has also been taken into account. A novel algorithm based on order reduction and finite difference discretization is developed in order to numerically treat the problem. The efficiency of the code is appraised by a numerical comparison which is found to be in a good correlation with the existing results. From the consequences of this study, it is deduced that the reduction in induced magnetic field and fluid’s velocity (in case of either pure or hybrid nanofluid) is associated with the enlarging values of magnetic Prandtl number and induced magnetic field parameter. Further, activation energy is responsible for enhancement in concentration. The hybrid nano-composition of GO–Fe3O4/EO can provide the thermal stability, prevent the corrosion and make the liquid to stay in high temperature.

Adsorption of molybdenum was carried out on two materials; potassium doped γ-Al2O3 (KA) and bentonite iron oxide composite (BIOC) with purpose of using in production of chromatographic 99mTc generators, for KA absorbent, different ranges of potassium loadings have been considered, for BIOC solid the used weight ratio was (Bentonite/Fe = 2/1). Samples were characterized by XRD and WDXRF. Adsorption of MoxOyz− species was carried out at pH 2.5 and 25 °C, effects of contact time and pH were studied. The Mo adsorption data onto used materials were well fitted using Freundlich and Langmuir models. Doped alumina samples showed higher adsorption capacities (∼90 mg g−1) than the usual alumina used in generator technology (∼60 mg g−1), whereas adsorption capacities of BIOC solid were in the range of (∼75 mg g−1). [ABSTRACT FROM AUTHOR]

The scientific community is inclined towards addressing environmental and energy concerns through sustainable means. Conventional processes such as chemical synthesis, involve the usage of environmentally harmful ligands and high tech facilities, which are time-consuming, expensive, energy-intensive, and require extreme conditions for synthesis. Plant-based synthesis is valuable and sustainable for the ecosystem. The use of plant-based precursors for nanoparticle synthesis eliminates the menace of toxic waste contamination. The present review elucidates that the plant based synthesized iron oxide and manganese oxide nanoparticles have tremendous and exceptional applications in various fields such as antimicrobial and antioxidative domains, environmental, electrical and sensing properties. Hence, the literature reviewed explains that plant based synthesis of nanoparticles is an adept and preferred technique. These important transition oxide metal nanoparticles have great applicability in ecological, environmental science as well as electrochemistry and sensing technology. Both these metal oxides display a stable and adaptable nature, which can be functionalized for a specific application, thus exhibiting great potential for efficiency. The current review epitomizes all the latest reported work on the synthesis of iron and manganese oxide nanoparticles through a greener approach along with explaining various significant applications keeping in view the concept of sustainability. [ABSTRACT FROM AUTHOR]

Short-range-ordered Fe(III) minerals such as ferrihydrite (Fh) are ubiquitous in the environment, are key players in biogeochemical cycling, and sorb trace elements and nutrients. As such, it is important to be able to identify the presence of such minerals in natural samples. Fh is commonly observed to be X‑ray amorphous and cannot be easily analyzed using X‑ray diffraction, meaning that spectroscopic methods such as X‑ray absorption or 57Fe Mössbauer spectroscopy (MBS) are necessary for accurate identification and quantification. Despite decades of research into Fh using MBS, there is a discrepancy in the literature about the exact parameters applicable to the mineral when measured at liquid helium temperature. Fh is frequently fitted with either one, two, or three hyperfine sextets with little interpretation applied to the meaning of each, which is problematic as a one sextet model does not account for the asymmetric lineshape frequently observed for Fh. Here, we address inconsistencies in the fitting of Fh and provide a more standardized approach to its identification by MBS. We present a systematic comparison of diferent fitting methods, notably based on Lorentzian and Voigt functions. We suggest that the most suitable approach to fitting pure Fh at liquid helium temperature is with two sextets (A and B) fitted using an extended Voigt-based function with the ability to apply probability distributions to each hyperfine parameter. 2-line Fh: A (δ = 0.49 mm/s; ε = 0.00 mm/s; Bhf = 50.1 T) and B (δ = 0.42 mm/s; ε = –0.01 mm/s; Bhf = 46.8 T) 6-line Fh: A (δ = 0.50 mm/s; ε = –0.03 mm/s; Bhf = 50.2 T) and B (δ = 0.40 mm/s; ε = –0.05 mm/s; Bhf = 47.1 T). We interpret the two sextets to be due to either diferences in the coordination environment of iron, i.e., in tetrahedral or octahedral sites, the presence of a disordered surface phase, or a combination of both. We hope that provoking a discussion on the use of MBS for Fh will help develop a greater understanding of this mineral, and other short-range ordered iron minerals, which are so important in environmental processes. [ABSTRACT FROM AUTHOR]

Different iron oxides were evaluated for the discoloration of methylene blue (MB) at neutral pH by heterogeneous photo-Fenton-like reactions with a UV-LED lamp. Fe3O4, α-Fe2O3, and a-FeOOH catalysts were synthesized and characterized by X-ray diffraction, scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared spectroscopy, and adsorption isotherms of N2. The results show high crystallinity and relatively low surface areas for Fe3O4 and α-Fe2O3, and amorphous structure with high surface area for the case of a-FeOOH. The discoloration of MB by iron oxides as catalysts was studied using UV-Vis spectroscopy. Despite the relative high adsorption of MB for magnetite (12%) compared to the other oxides, it shows a slow discoloration kinetics. Besides, amorphous oxide (named a-FeOOH) shows a higher discoloration kinetics with negligible adsorption capacity. The pseudo first-order kinetic constant values for Fe3O4, α-Fe2O3, and a-FeOOH are 5.31 × 10−3, 6.89 × 10−3, and 13.01 × 10−3 min−1; and the discoloration efficiencies at 120 min were 56, 60, and 82%, respectively. It was testified that low crystallinity iron oxide can be used in the efficient discoloration of MB by photo-Fenton process with a hand UV-A lamp.

Iron(II) oxide, wüstite, is the iron oxide with the lowest oxygen content. Under ambient conditions it is metastable for two reasons: (1) it undergoes eutectoid decomposition to Fe and Fe3O4 below ≈570° C, and (2) depending on temperature, it is thermodynamically stable only for very low oxygen partial pressures, down to below 10−20 bar. Hence, for the growth of single crystals from the melt, the growth atmosphere must contain reducing components to keep the oxygen partial pressure on the required low level. With Ar/CO2/CO mixtures this aim can be reached. It is shown experimentally and by thermodynamic calculation, that the grown crystals contain carbon inclusions. Theoretically it is shown that wüstite crystals without carbon inclusions could be grown in humid N2/H2 mixtures. First experiments are presented in this article, but a further adjustment of experimental parameters is required. [ABSTRACT FROM AUTHOR]

Keywords: iron oxide; Langmuir isotherm; magnetic separation; surface modification; U(VI) adsorption EN iron oxide Langmuir isotherm magnetic separation surface modification U(VI) adsorption 333 347 15 05/12/22 20220501 NES 220501 1 Introduction The energy derived from nuclear reactor is a promising option for providing electricity without the emission of toxic greenhouse gases [[1]], [[2]], [[3]], [[4]]. Graph: Figure 8: SEM image of (a) Fe3O4, (b) Fe-Si, (c) Fe-SUC, and (d) U(VI) loaded Fe-SUC (Fe-SUC-U). 2.4.3 Effect of U(VI) concentration on adsorption The effect of U(VI) concentration on the adsorption of U(VI) on Fe-SUC was determined by batch equilibration method. [Extracted from the article]

Physical and chemical methods have been developed for water and wastewater treatments. Adsorption is an attractive method due to its simplicity and low cost, and it has been widely employed in industrial treatment. In advanced schemes, chemical oxidation and photocatalytic oxidation have been recognized as effective methods for wastewater-containing organic compounds. The use of magnetic iron oxide in these methods has received much attention. Magnetic iron oxide nanocomposite adsorbents have been recognized as favorable materials due to their stability, high adsorption capacities, and recoverability, compared to conventional sorbents. Magnetic iron oxide nanocomposites have also been reported to be effective in photocatalytic and chemical oxidation processes. The current review has presented recent developments in techniques using magnetic iron oxide nanocomposites for water treatment applications. The review highlights the synthesis method and compares modifications for adsorbent, photocatalytic oxidation, and chemical oxidation processes. Future prospects for the use of nanocomposites have been presented.

The aim of this research was to investigate ciprofloxacin (CIP) removal efficiency from aqueous solutions by using Fe3O4 nanoparticles @Trioctylmethylammonium thiosalicylat Ionic liquid (Fe3O4 NP@ TOMATS IL) as a new magnetic nanoadsorbent. The adsorbent was characterized by field emission scanning electron microscope-energy dispersive spectroscopy (FESEM-EDS), mapping, Fourier transform infrared spectroscopy (FT-IR), the Brunauer–Emmett–Teller (BET), X-ray powder diffraction (XRD). The effects of solution pH, adsorbent dose, contact time, initial CIP concentration, and temperature on CIP removal were also investigated. In optimal conditions such as pH = 5.6, CIP concentration = 30 mg/L, adsorbent dose = 0.15 g, temperature = 30 °C, contact time = 90 min, the removal efficiency in synthetic and real wastewater were obtained 87 and 73%, respectively. Batch experiments were carried out to study the sorption Kinetics, thermodynamics, and equilibrium isotherms of CIP with magnetic nanoadsorbent. The results show that all of the above factors influence CIP removal. The Langmuir adsorption isotherm fits the adsorption process well, with the pseudo second-order model describing the adsorption kinetics accurately. The thermodynamic parameters indicate that adsorption is mainly physical adsorption. Recycling experiments revealed that the behavior of adsorbent is maintained after recycling for four times. [ABSTRACT FROM AUTHOR]

Chromium is well-thought-out heavy metal which is one of the enormously lethal due to its cancer-causing nature. In this study, iron oxide is used as adsorbent for chromate removal from aqueous solution as a function of pH, time, temperature, concentration of adsorbate and media dosage. The influence of pH on Cr (VI) sorption by iron oxide reveals that adsorption is significantly increased as pH is decreased from 8 to 2. The sorption rate is detected to be higher in the beginning and then it remains constant after 120 min of equilibrium time. The removal of Cr (VI) is found to be greater at higher temperature, which confirms the endothermic nature of Cr (VI) adsorption by iron oxide. Whereas, the kinetic investigations confirm that the chromate adsorption follows the pseudo second order with kinetic energy in the range of 8.4–83.7 kJ mol−1. [ABSTRACT FROM AUTHOR]

The purpose of this study was to review the use of the magnetic targeting technique, characterized by magnetic driving compounds based on superparamagnetic iron oxide nanoparticles (SPIONs), as drug delivery for a specific brain locus in gliomas. We reviewed a process mediated by the application of an external static magnetic field for targeting SPIONs in gliomas. A search of PubMed, Cochrane Library, Scopus, and Web of Science databases identified 228 studies, 23 of which were selected based on inclusion criteria and predetermined exclusion criteria. The articles were analyzed by physicochemical characteristics of SPIONs used, cell types used for tumor induction, characteristics of experimental glioma models, magnetic targeting technical parameters, and analysis method of process efficiency. The study shows the highlights and importance of magnetic targeting to optimize the magnetic targeting process as a therapeutic strategy for gliomas. Regardless of the intensity of the patterned magnetic field, the time of application of the field, and nanoparticle used (commercial or synthesized), all studies showed a vast advantage in the use of magnetic targeting, either alone or in combination with other techniques, for optimized glioma therapy. Therefore, this review elucidates the preclinical and therapeutic applications of magnetic targeting in glioma, an innovative nanobiotechnological method.

In this study, iron oxide, nickel oxide, and nickel-iron oxide nanostructured particles were produced by the hydrothermal method. X-ray diffraction (XRD) and SEM measurements were performed to investigate the physical properties of these nanostructured particles. According to the XRD results, the crystal properties of these particles were determined. From the SEM images, these particles understood to be nano-structured. The electrodes were examined for electrochemical properties by using these nanostructured particles. Electrochemical measurements of the produced electrodes were performed, and capacitance values and impedance spectra of the electrodes were determined. The specific capacitance values of the iron oxide, nickel-iron oxide, and nickel oxide nanostructured particles, respectively are 30 F/g, 55 F/g, and 67 F/g. Also, the photocatalytic activities of nanostructured particles were investigated. This examination methylene blue (MB) was used and made under a xenon lamp. In light of our findings, it was observed that high photocatalytic degradation rate. Nickel-iron oxide nanostructured particles, the degradation of MB were found to be about 87%. [ABSTRACT FROM AUTHOR]

The oxygen fugacity in the interior of the Earth is largely controlled by iron-bearing minerals. Recent studies have reported various iron oxides with chemical compositions between FeO and Fe3O4 above ~10 GPa. However, the stabilities of these high-pressure iron oxides remain mostly uninvestigated. In this study, we performed in situ X-ray diffraction (XRD) measurements in a laser-heated diamond-anvil cell (DAC) to determine the phase relations in both Fe5O6 and Fe4O5 bulk compositions to 61 GPa and to 2720 K. The results show that Fe5O6 is a high-temperature phase stable above 1600 K and ~10 GPa, while FeO + Fe4O5 are formed at relatively low temperatures. We observed the decomposition of Fe5O6 into 2FeO + Fe3O4 above 38 GPa and the decomposition of Fe4O5 into FeO + h-Fe3O4 at a similar pressure range. The coexistence of FeO and Fe3O4 indicates that none of the recently discovered compounds between FeO and Fe3O4 (i.e., Fe5O6, Fe9O11, Fe4O5, and Fe7O9) are formed beyond ~40 GPa at 1800 K, corresponding to conditions in the shallow lower mantle. Additionally, as some superdeep diamonds have genetic links with these high-pressure iron oxides, our results give constraints on pressure and temperature conditions of their formation. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) is now an established NOx removal technology for industrial flue gas as well as for diesel engine exhaust gas. However, it is still a big challenge to develop a novel low-temperature catalyst for NH3-SCR of NOx, especially at a temperature below 200°C. In the past few years, many studies have demonstrated the potential of iron (Fe)-based catalysts as low-temperature catalysts for NH3-SCR of NOx. Herein, we summarize the recent progress and performance of Fe-based catalysts for low-temperature NH3-SCR of NOx. Catalysts are divided into three categories: single FexOy, Fe-based multimetal oxide, and Fe-based multimetal oxide with support catalysts. The catalytic activity and selectivity of Fe-based catalysts are systematically analyzed and summarized in light of some key factors such as activation energy, specific surface area, morphology, crystallinity, preparation method and precursor, acid sites, calcination temperature, other metal dopant/substitute, and redox property of catalysts. In addition, H2O/SO2 tolerance and the NH3-SCR reaction mechanism over Fe-based catalysts, including Eley-Rideal and Langmuir-Hinshelwood mechanism, are emphasized. Lastly, the perspectives and future research directions of low-temperature NH3-SCR of NOx are also proposed. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction (SCR) is now an established NOx removal technology for industrial flue gas as well as for diesel engine exhaust gas. However, it is still a big challenge to develop a novel low-temperature catalyst for NH3-SCR of NOx, especially at a temperature below 200°C. In the past few years, many studies have demonstrated the potential of iron (Fe)-based catalysts as low-temperature catalysts for NH3-SCR of NOx. Herein, we summarize the recent progress and performance of Fe-based catalysts for low-temperature NH3-SCR of NOx. Catalysts are divided into three categories: single FexOy, Fe-based multimetal oxide, and Fe-based multimetal oxide with support catalysts. The catalytic activity and selectivity of Fe-based catalysts are systematically analyzed and summarized in light of some key factors such as activation energy, specific surface area, morphology, crystallinity, preparation method and precursor, acid sites, calcination temperature, other metal dopant/substitute, and redox property of catalysts. In addition, H2O/SO2 tolerance and the NH3-SCR reaction mechanism over Fe-based catalysts, including Eley-Rideal and Langmuir-Hinshelwood mechanism, are emphasized. Lastly, the perspectives and future research directions of low-temperature NH3-SCR of NOx are also proposed. [ABSTRACT FROM AUTHOR]

A novel Mg-bearing iron oxide Mg 0.87 (1) Fe 4.13 (1) 2 + Fe 4 3 + O 11 $ \begin{array} {} {\rm{M}}{{\rm{g}}_{0.87(1)}}{\rm{Fe}}_{4.13(1)}^{2 + }{\rm{Fe}}_4^{3 + }{{\rm{O}}_{11}}\end{array} $ was synthesized at 12 GPa and 1300 °C using a large volume press. Rietveld structural analysis was conducted with a laboratory X‑ray diffraction pattern obtained at ambient conditions. The crystal structure, which has one oxygen trigonal prism site and four octahedral sites for the cations, was found to be isostructural with Ca2Fe7O11. The unit-cell lattice parameters are a = 9.8441(5) Å, b = 2.8920(1) Å, c = 14.1760(6) Å, β = 99.956(4)°, V = 397.50(3) Å3, and Z = 2 (monoclinic, C2/m). Mg and Fe cations are disordered on the trigonal prism site and on two of the four octahedral sites, and the remaining Fe is accommodated at the other two octahedral sites. The present structure is closely related to the other recently discovered Fe oxide structures, e.g., Fe4O5 and Fe5O6, by distortion derived either from incorporation (Fe4O5) or removal (Fe5O6) of an edge-shared FeO6 single octahedral chain in their structures. The present synthesis at deep upper mantle conditions and the structural relationships observed between various novel Mg-Fe oxides indicate that a series of different phases become stable above 10 GPa and that their relative stabilities (Fe2+/Fe3+) must be controlled by oxygen fugacity. [ABSTRACT FROM AUTHOR]

In recent years, nanoparticle formulations utilizing magnetic materials have started gaining more consideration in the biomedical arena due to their inherent superparamagnetic/paramagnetic nature paving ways to develop assays and sensors benefitting mostly magnetic separation technique. Coupled with the developments in the synthetic field in obtaining controlled-sized particles and surface functionalities, a variety of sensitive and selective assays have been developed ranging from detection/separation/enrichment of antibodies, enzymes, proteins, and nucleic acids to whole cells, virus, and pathogens utilizing a variety of signal transduction mechanisms including fluorescence, surface plasmon resonance, and magnetic resonance. In addition to ongoing research in this field, there are already commercialized products engineered to detect and quantify biomolecules with proper surface formulations. Owing to the immensity of applications of magnetic particles, in this article, recent trends in the design and applications of iron oxide nanoparticles will be reviewed.

The purpose of this study was to review the use of the magnetic targeting technique, characterized by magnetic driving compounds based on superparamagnetic iron oxide nanoparticles (SPIONs), as drug delivery for a specific brain locus in gliomas. We reviewed a process mediated by the application of an external static magnetic field for targeting SPIONs in gliomas. A search of PubMed, Cochrane Library, Scopus, and Web of Science databases identified 228 studies, 23 of which were selected based on inclusion criteria and predetermined exclusion criteria. The articles were analyzed by physicochemical characteristics of SPIONs used, cell types used for tumor induction, characteristics of experimental glioma models, magnetic targeting technical parameters, and analysis method of process efficiency. The study shows the highlights and importance of magnetic targeting to optimize the magnetic targeting process as a therapeutic strategy for gliomas. Regardless of the intensity of the patterned magnetic field, the time of application of the field and nanoparticle used (commercial or synthesized), all studies showed a vast advantage in the use of magnetic targeting, either alone or in combination with other techniques, for optimized glioma therapy. Therefore, this review elucidates the preclinical and therapeutic applications of magnetic targeting in glioma, an innovative nanobiotechnological method. [ABSTRACT FROM AUTHOR]

The iron (Fe) L2,3-edge X-ray absorption near-edge structure (XANES) spectrum is sensitive to the local coordination environment around the Fe metal center, making it a useful probe for understanding Fe mineral speciation. The two dominant spectral peaks in the Fe L3-edge are parameterized according to the difference in the energy position (ΔeV), and the quotient (intensity ratio) of the two peaks' maxima. Variations in the ΔeV value are strongly linked to factors that impact on the strength of the ligand field (e.g., Fe valence state, coordination number, and the nature of ligand bonding). The intensity ratio is affected by the strength of the ligand field and by the composition of the resultant molecular orbitals. The Fe valence state also strongly affects the intensity ratio, and an intensity ratio equal to one can be used to distinguish between Fe2+ and Fe3+ minerals. The effects of polyhedral distortion on the magnitudes of ΔeV and intensity ratio values were tested by considering the Fe oxide and -oxy- hydroxide mineral system, in which ligand effects are limited to the differences between the oxygen and hydroxyl ligands. In this system, the distribution of Fe oxide and -oxy-hydroxide minerals on a ΔeV vs. intensity ratio two-parameter plot could be explained by considering the Fe valence state, the ligand chemistry and the site symmetry of the Fe polyhedra. Furthermore, the ΔeV and intensity ratio values were found to be anti-correlated with respect to the various distortion measures considered in this study (e.g., polyhedral volume distortion percentage). This two-parameter plot is thus presented as a standard-less phase-specific identification tool for use in Fe speciation studies, applicable to both natural systems (e.g., aerosols, aquatic colloids) as well as to engineered systems (e.g., nanoparticle synthesis). A major advantage of this technique is that it is applicable to both crystalline and poorly crystalline phases, thus enhancing our ability to study amorphous and nano-crystalline phases that are typically difficult to characterize using X-ray diffraction techniques. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) nanosheets were hybridized with Fe3O4 nanoparticles (NPs) to form magnetic GO (MGO) and were further labeled by [68Ga]GaCl3 as a potential drug delivery system. Paper chromatography, Fourier transform infra red (FTIR) spectroscopy, low-angle X-ray diffraction (XRD), CHN and atomic force microscopy (AFM) were utilized to characterize the trinary composite ([68Ga]@MGO). Biological evaluations of the prepared nanocomposite were performed in normal Sprague Dawley rats and it was found to be a possible host for theranostic radiopharmaceuticals. The results showed that the grafting of Fe3O4 NPs on nanocomposite reduced the unwanted liver and spleen uptakes and increased the ratio of kidney/liver uptake from 0.037 to 1.07, leading to the fast removal of radioactive agent and less imposed radiation to patients. The high level of hydrogen bonding caused by the presence of functional groups is responsible for this effect. Considering the accumulation of the tracer in vital organs of rat (especially brain), efficient iron oxide grafting, fast wash-out, the short half-life gallium-68 and less imposed radiation doses to patients, this nanocomposite could be a suitable candidate for positron emission tomography (PET) studies and imaging applications. [ABSTRACT FROM AUTHOR]

Objective: Cyclodextrins have been used to catalyze chemical reactions in the synthesis of different materials. The aim of this study is to produce nanoparticles using cyclodextrin as a nanoreactor. Methods: In this study, nanoparticles from the solid phase of iron oxide (Fe3O4), copper oxide (CuO) and metallic silver (Ago) were obtained through hydrothermal synthesis at 100 and 150°C for six hours. This was produced for cyclodextrin glycosyltransferase from Bacillus lehensis isolated from wastewater of a cassava flourmill. The nanoparticles were characterized through x-ray diffraction Fourier transform infrared spectroscopy and field emission gun scanning electron microscopy. Results: The images demonstrated that the nanoparticles exhibited a polyhedric shape with a diameter of 100 nm for Fe4O3, an irregular oval shape with a diameter of 45 nm for CuO and a platelet shape with a diameter of 138 nm for Ago. Conclusion: Based on this characterization, the proposed technique proved to be an efficient, low-cost, convenient method for the production of sub-micrometric and nanometric solid phases and can likely be scaled up for industrial use. The results demonstrate the possibility of producing nanoparticles using cyclodextrin as a nanoreactor. [ABSTRACT FROM AUTHOR]

We demonstrate in this study that natural green rust nanoparticles and their synthetic analogs can be complex polycrystalline phases composed of crystallites only a few nanometers in size, and they often include nanometer-sized regions of amorphous material. The natural green rusts are Zn-bearing pseudo-hexagonal platelets previously identified by us in the contaminated mine drainage of the former Ronneburg uranium mine in Germany (Johnson et al. 2014). We also identified Ni- and Cubearing green rust platelets in the sediment underlying the drainage outflow 20 m downstream, and, using dark-field transmission electron microscopy (DF-TEM), found that these natural green rusts are not usually structurally coherent single crystals. Synthetic sulfate green rusts are also polycrystalline and composed of crystallites of only a few nanometers in size, though different synthesis conditions produced different patterns of polycrystallinity. While pseudo-hexagonal platelets are the typical morphology of green rust, we also synthesized green rust nanorods, which have not previously been reported. In addition to the known characteristics of green rusts (including a very large aspect ratio and surface area to volume ratio, and the redox properties allowed by the structural mixture of Fe2+ and Fe3+), these polycrystalline platelets exhibit a high abundance of defect sites and likely a rough surface topography. The combination of these characteristics has important implications for the reactivity of green rust with biogeochemical interfaces in natural and anthropogenic systems. [ABSTRACT FROM AUTHOR]

We simulated the redox decomposition of magnesium-siderite at pressures and temperatures corresponding to the top of the Earth's D″ layer (135 GPa and 2650 K). It transforms into new phases, with unexpected stoichiometry. We report their crystal structure, based on single-crystal synchrotron radiation diffraction on a multi-grain sample, using a charge-flipping algorithm. Mg2Fe2(C4O13) is monoclinic, a = 9.822(3), b = 3.9023(13), c = 13.154(5) Å, β = 108.02(3)°, V = 479.4(3) Å3 (at 135 GPa). It contains tetrahedrally coordinated carbon units, corner-shared in truncated C4O13 chains. Half of the cations are divalent, and half trivalent. The carbonate coexists with a new iron oxide, Fe13O19, monoclinic, a = 19.233(2), b = 2.5820(13), c = 9.550(11) Å, β = 118.39(3)°, V = 417.2(5) Å3 (at 135 GPa). It has a stoichiometry between hematite, Fe2O3, and magnetite, Fe3O4. The formation of these unquenchable phases indicates, indirectly, the formation of reduced-carbon species, possibly diamond. These structures suggest the ideas that the mineralogy of the lower mantle and D″ region may be more complex than previously estimated. This is especially significant concerning accessory phases of fundamental geochemical significance and their role in ultra-deep iron-carbon redox coupling processes, as well as the iron-oxygen system, which certainly play an important role in the lower mantle mineral phase equilibria. [ABSTRACT FROM AUTHOR]

The ferric oxyhydroxide minerals akaganéite and schwertmannite are associated with acidic environments and iron alteration on Earth and may be present on Mars as well. These minerals have a tunnel structure and are crystallographically related. The extended visible region reflectance spectra of these minerals are characterized by a broad Fe3+ electronic transition centered near 0.92 µm, a reflectance maximum near 0.73 µm, and a shoulder near 0.59 µm. The near-infrared (NIR) reflectance spectra of each of these minerals are dominated by broad overtones and combinations of the H2O vibration features. These occur near 1.44-1.48 and 1.98-2.07 µm (~6750-6950 and 4830-5210 cm-1) in akaganéite spectra, while in schwertmannite spectra they occur at 1.44-1.48 and 1.95-2.00 µm (~6750-6950 and 5005-5190 cm-1). Additional bands due to OH vibrational overtones are found near 1.42 µm (~7040 cm-1) in akaganéite and schwertmannite spectra and due to OH combination bands in akaganéite spectra at 2.46 µm (4070 cm-1) with weaker components at 2.23-2.42 µm (4134-4492 cm-1). A strong and broad band is observed near 2.8-3.1 µm (~3300-3600 cm-1) in reflectance and transmittance spectra of akaganéite and schwertmannite due to overlapping OH and H2O stretching vibrations. H2O bending vibrations occur near 1620 cm-1 (~6.17 µm) in akaganéite spectra and near 1630 cm-1 (~6.13 µm) in schwertmannite spectra with additional bands at lower frequencies due to constrained H2O molecules. OH bending vibrations occur near 650 and 850 cm-1 (~15.4 and 11.8 µm) in akaganéite spectra and near 700 cm-1 (~14.3 µm) in schwertmannite spectra. Sulfate vibrations are observed for schwertmannite as a v3 triplet at 1118, 1057, and 1038 cm-1 (~8.9, 9.5, and 9.6 µm), v1 at 982 cm-1 (~10.2 µm), v4 near 690 cm-1 (~14.5 µm), and v2 at 608 cm-1 (~16.5 µm). Fe-O bonds occur near 410-470 cm-1 (µm) for akaganéite and schwertmannite. Both minerals readily absorb H2O molecules from the environment and adsorb them onto the mineral surfaces and incorporate them into the tunnels. If akaganéite and schwertmannite were present on the surface of Mars they could enable transport of H2O from the near-surface to the atmosphere as the partial pressure of H2O varies diurnally. [ABSTRACT FROM AUTHOR]

The reduction of HSO to SO occurs with a relatively good efficiency only at high temperatures, in the presence of catalysts. Some experimental results, regarding conversion of sulfuric acid (96 wt.%) to sulfur dioxide and oxygen, are reported. The reduction has been performed at 800 - 900°C and atmospheric pressure, in a tubular quartz reactor. The following commercial catalysts were tested: Pd/AlO (5 wt.% and 0.5 wt.% Pd), Pt/AlO (0.1 wt.% Pt) and α-FeO. The fresh and spent catalysts were characterized by X-Ray diffraction and BET method. The highest catalytic activity was determined for 5 wt.% Pd/AlO, a conversion of 80% being obtained for 5 hours time on stream, at 9 mL h flow rate of 96 wt.% HSO. A conversion of 64% was determined for 0.5 wt.% Pd/AlO and 0.1 wt.% Pt/AlO. For α-FeO, a less expensive catalyst, a conversion of 61% for about 60 hours was obtained. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Two sets of precipitates collected from stream sediments in the Monte Romero (MR) and Tinto Santa Rosa (TSR) abandoned mine sites--located in the Iberian Pyrite Belt (IPB) of Spain--were identified as the iron oxyhydroxysulfate nanomineral schwertmannite using X-ray diffraction (XRD) and bulk digestion and were further studied in great detail using analytical high-resolution transmission electron microscopy (HRTEM). Extensive HRTEM observations suggest that schwertmannite should not be described as a single-phase mineral with a repeating unit cell, but as a polyphasic nanomineral with crystalline areas spanning less than a few nanometers within an amorphous matrix. The d-spacings measured from lattice fringes within schwertmannite's needles match with d-spacings of the known transformation products of schwertmannite (goethite and jarosite). This finding implies that the initial stages of schwertmannite transformation occur as a gradual structural reordering at the nanoscale. Energy-dispersive X-ray analysis applied across individual schwertmannite needles with ~3 nm spot size resolution reveal a decreasing ratio of sulfur to iron and silicon to iron from the surface of the needle to the core with the silicon to iron ratio consistently higher than the sulfur to iron ratio. Amorphous silicon-rich precipitates were identified on the surface of the TSR schwertmannite. All of these observations explain why the measured solubility product of schwertmannite is variable, resulting in calculated stability fields that differ greatly from sample to sample. Arsenic is the most abundant trace element in these samples [MR: 0.218(1) wt% and TSR: 0.53(2) wt%], keeping in mind that schwertmannite has been shown to be a key player in the cycling of this element on a global basis, particularly from the IPB. Furthermore, arsenic in the TSR schwertmannite is associated with crystalline areas within its needle matrix, implying that schwertmannite-derived goethite nanocrystals may be an important host of arsenic. [ABSTRACT FROM AUTHOR]

Magnetic iron oxide (maghemite, Fe3O4) particles were encapsulated with polyester resin. The resulting magnetic powders were characterized by Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), Fritsch particle sizer, scanning electron microscopy (SEM), X-ray diffractometer (XRD) and vibrating sample magnetometer (VSM) measurements. FTIR and XRD confirmed the presence of iron oxide in polymer phase. The TGA and DSC measurements indicated the magnetic polymer particles have more than 50% iron oxide content and high thermal stability. SEM revealed that all maghemite particles were embedded in the polymer phase. The size distribution analysis of prepared magnetic particles has shown that the mean diameter of the bare iron oxide particles slightly increased with encapsulation. According to our magnetometry data, shape of the loops evidences the ferromagnetic character of the material and no evidence of superparamagnetism was seen. [ABSTRACT FROM AUTHOR]

The theoretical infrared spectrum of hematite (α-Fe2O3) was computed using ab initio quantum mechanical calculations. Frequencies of the normal vibrational modes and Born effective charges were computed using the density functional theory (DFT) with and without the addition of a Hubbard U correction. The infrared reflection spectra of a single crystal of hematite were calculated as well as the infrared powder absorption spectrum using an electrostatic model that takes into account the shape of hematite particles. The theoretical behavior of the absorption bands is in agreement with experimental observations and provides a firm basis for the interpretation of the bands in term of vibrational modes. Overall, results suggest that the use of DFT + U, which is necessary to describe correctly the electronic and magnetic properties of hematite, does not improve noticeably the prediction of vibrational properties. [ABSTRACT FROM AUTHOR]