Solid Iron Research Articles

Silver nitroprusside: Atypical coordination within the metal nitroprussides series

The nitroprusside complex anion forms an insoluble salt, of formula unit Ag2[Fe(CN)5NO], when it reacts with an aqueous solution of Ag+. Related to the high insolubility of silver halides, silver nitroprusside is a good intermediate to obtain soluble nitroprussides of alkaline, alkaline earth and trivalent transition metals. No other applications for that solid have been reported, probably because its crystal structure and related properties are unknown. This contribution reports the crystal structure for the titled compound from X-ray powder diffraction data and its refinement using the Rietveld method. It crystallizes with a monoclinic unit cell, in the Pc space group, with cell parameters: a=7.4254(3), b=6.4121(2), c=11.8729(2)Å, β=115.16(1)°. The crystal structure has two sites for the silver atom, corresponding to its coordination two and three to the N ends of CN groups. Calculation of the radial distribution function and IR and UV–Vis spectra provided the a priori structural information required to support the selected structural model to be refined. Such information was then used to validate the refined structure. The structure of this compound is atypical within the metal nitroprussides series. The thermal decomposition in air and nitrogen atmosphere of the title compound was studied from thermogravimetry and IR combined techniques. In the solid residues metallic silver and iron oxide (hematite) were identified.

Arsenic Cycling in Hydrocarbon Plumes: Secondary Effects of Natural Attenuation.

Monitored natural attenuation is widely applied as a remediation strategy at hydrocarbon spill sites. Natural attenuation relies on biodegradation of hydrocarbons coupled with reduction of electron acceptors, including solid phase ferric iron (Fe(III)). Because arsenic (As) adsorbs to Fe-hydroxides, a potential secondary effect of natural attenuation of hydrocarbons coupled with Fe(III) reduction is a release of naturally occurring As to groundwater. At a crude-oil-contaminated aquifer near Bemidji, Minnesota, anaerobic biodegradation of hydrocarbons coupled to Fe(III) reduction has been well documented. We collected groundwater samples at the site annually from 2009 to 2013 to examine if As is released to groundwater and, if so, to document relationships between As and Fe inside and outside of the dissolved hydrocarbon plume. Arsenic concentrations in groundwater in the plume reached 230 µg/L, whereas groundwater outside the plume contained less than 5 µg/L As. Combined with previous data from the Bemidji site, our results suggest that (1) naturally occurring As is associated with Fe-hydroxides present in the glacially derived aquifer sediments; (2) introduction of hydrocarbons results in reduction of Fe-hydroxides, releasing As and Fe to groundwater; (3) at the leading edge of the plume, As and Fe are removed from groundwater and retained on sediments; and (4) downgradient from the plume, patterns of As and Fe in groundwater are similar to background. We develop a conceptual model of secondary As release due to natural attenuation of hydrocarbons that can be applied to other sites where an influx of biodegradable organic carbon promotes Fe(III) reduction.

Characterization of Iron Phthalocyanine as the Cathode Active Material for Lithium-Ion Batteries

The developed thermodynamic functions for the determination of Gibbs free energy, enthalpy, and entropy of formation of solid lithium-iron phthalocyanine (LixFePc) from solid lithium and iron phthalocyanine as a function of x, defined as g-moles of the intercalated lithium per g-mole of iron phthalocyanine, at a fixed set of temperature and pressure conditions are presented. In addition, a proposed expression for the evaluation of lithium diffusion coefficient in solid iron phthalocyanine as a function of both x and temperature, and the experimental results from the ongoing research/development work on the lithium/iron phthalocyanine cells are included

Earth Science Revisited: Expansion-Based Hypothesis for Explaining Global Phenomena

Basic tenets of plate tectonics, like, plunging of a solid plate within solid mantle and the incidence of convection in it causing plate motion are doubtful as scientific explanations. With the help of an expansion-based model of the Earth, which was devoid of oceans, it has been conceived that initially the Earth’s mantle was adequately fluid and suitable for expansion owing to association of ocean-forming water. Matching thickness of outer core and extent of expansion reveals that due to expansion-caused by extra-terrestrial gravitational attraction-a void zone, termed outer core was developed between the mantle and the solid iron core. Presence of such a zone in the planet’s deep interior would give rise to an additional force of reversely directed gravity in the inner core region where, in consequence, temperature and pressure would be considerably low. Hence, it can be interpreted that the Earth’s inner core, from where magnetic lines of force emerge, is a huge dipolar magnet. With opening of the pseudo-fluid zone in the deep interior of the Earth, the inner core remained within it in a suspended condition, giving rise to new magnetic phenomena like pole reversals and polar wandering in response to extra-terrestrial magnetic influences.

Design and synthesis of micron-sized spherical aggregates composed of hollow Fe2O3 nanospheres for use in lithium-ion batteries.

A novel structure denoted a "hollow nanosphere aggregate" is synthesized by introducing nanoscale Kirkendall diffusion to the spray pyrolysis process. The hollow Fe2O3 nanosphere aggregates with spherical shape and micron size are synthesized as the first target material. A solid iron oxide-carbon composite powder that is prepared by a one-pot spray pyrolysis process is transformed into the hollow Fe2O3 nanosphere aggregates by sequential post-pyrolysis treatments under reducing and oxidizing atmospheres. The nanoscale Kirkendall diffusion plays a key role in the formation of the hollow Fe2O3 nanosphere aggregates with spherical shape and micron size. The unique structure of the hollow Fe2O3 nanosphere aggregates results in their superior electrochemical properties as an anode material for lithium ion batteries by improving the structural stability during cycling. The hollow metal oxide nanosphere aggregates with various compositions for wide applications including energy storage can be prepared by the simple fabrication method introduced in this study.

Performance of a zero valent iron-based anaerobic system in swine wastewater treatment

In this paper, short-term exposure experiments with different ZVI concentrations were conducted to research the effects of ZVI adding on the anaerobic system for treating swine wastewater. Increasing the ZVI dose had a stimulatory effect on COD removal and CH4 production possibly due to a higher corrosion-induced H2 and dissolved ferrous ions, which could stimulate the methanogenesis and thus the biodegradation. In addition, the abiotic corrosion reactions such as flocculation, adsorption and precipitation were inevitable to removal some suspended COD. However, high ZVI doses had a potential risk on microorganism due to the present of large numbers of solid iron species in sludge, which likely encapsulated the cells and even damaged the cellular structure. Taken as a whole, the most enhancing effect induced by ZVI was observed at the rZVI/VSS of 2.63, and the maximum efficiency of per ZVI adding occurred at the rZVI/VSS of 0.74. But the ZVI concentration of 50g/L (the rZVI/VSS was 5.26) was proved too high to facilitate microorganism activity, considering the higher LDH leakage and lower intracellular ATP level than the only sludge system.

Assessment of Metal Enrichment Factors in Waters Draining a Mixed-Land-Use Catchment

Pollution assessment in a given area depends mostly on the precise determination of the so-called background values. In this work, enrichment factors (EFs) for iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in suspended solids (SS) of a stream draining a rural catchment (NW Spain) were determined to assess whether the observed concentrations of these metals represent natural or contaminated levels. Aluminum was used as a normalizer element. Four approaches were used for defining background values used in the EF analyses: a local background value for metals concentrations in SS, a local background value for metals concentrations in C-horizon soils, mean crust values, and mean shale values. The most satisfactory result was obtained when using local background values for metals concentrations of SS, suggesting that on average the Fe, Mn, Cu, and Zn concentrations measured represent natural levels. However, some signs of enrichment were observed (16–28 percent of the samples with EF > 1.5).

High-temperature miscibility of iron and rock during terrestrial planet formation

The accretion of a terrestrial body and differentiation of its silicate/oxide mantle from iron core provide abundant energy for heating its interior to temperatures much higher than the present day Earth. The consequences of differentiation on the structure and composition of planets are typically addressed considering only the interaction of molten iron with an immiscible ‘rocky’ phase. We demonstrate that mixing in a representative system of liquid or solid MgO and liquid iron to a single homogeneous liquid occurs at sufficiently low temperature to be present in the aftermath of a giant impact. Applying the thermodynamic integration technique to density functional theory molecular dynamics simulations, we determine the solvus closure temperature for the Fe–MgO system for pressures up to 400 GPa. Solvus closure occurs at ∼4000 K at low pressure, and has a weak positive pressure dependence, such that its gradient with respect to depth is less steep than an adiabatic temperature profile. This predicts a new mode of core–mantle differentiation following the most energetic giant impacts, with exsolution of iron from the mixture beginning in the outer layers of the planet. We demonstrate that high-temperature equilibration results in delivery of nominally insoluble Mg-rich material to the early core. Since MgO is the least soluble major mantle component in iron at low temperatures, these results may represent an upper bound on temperature for mixing in terrestrial planets.

Dissolution rate of solid iron into liquid Fe-C alloy

Dissolution rate of solid iron into liquid Fe-C alloy was investigated using a sampling method at a fixed reaction area. The initial carbon concentration of the bulk liquid Fe-C alloy was set as 4.23, 3.29 and 2.17 wt% for the experiments at 1503, 1597, and 1688 K, respectively. The temperature dependence of the rate constant was obtained as follows: \(\ln k(m/s) = - 3.47 - \tfrac{{8905}} {T}\). The activation energy was estimated to be 74 kJ/mol. A dimensionless analysis was carried out separately to confirm the rate-determining step. The measured values showed reasonable agreement with the calculated values from the dimensionless analysis. Therefore, it is concluded that the mass transfer in the liquid boundary layer is the rate-determining step for the dissolution of solid iron in the liquid Fe-C alloy. The liquid boundary layer was estimated approximately 100 μm, which slightly decreased with increasing temperature. Present experimental results would be helpful to understand the mechanism of liquid iron formation in the ironmaking and steelmaking processes as well as in the reduction of iron-containing slags.

Treatment of nanofiltration concentrates of mature landfill leachate by a coupled process of coagulation and internal micro-electrolysis adding hydrogen peroxide

In this study, a coupled process of coagulation and aerated internal micro-electrolysis (IME) with the in situ addition of hydrogen peroxide (H2O2) was investigated for the treatment of nanofiltration (NF) concentrate from mature landfill leachate. The acceptable operating conditions were determined as follows: initial pH 4, polymeric aluminium chloride dosage of 525 mg-Al2O3/L in the coagulation process, H2O2 dosage of 0.75 mM and an hydraulic retention time of 2 h in an aerated IME reactor. As a result, the removal efficiencies for chemical oxygen demand (COD), total organic carbon, UV254 and colour were 79.2%, 79.6%, 81.8% and 90.8%, respectively. In addition, the ratio of biochemical oxygen demand (BOD5)/COD in the final effluent increased from 0.03 to 0.31, and that of E2/E4 from 12.4 to 38.5, respectively. The results indicate that the combined process is an effective and economical way to remove organic matters and to improve the biodegradability of the NF concentrate. Coagulation process reduces the adverse impact of high-molecular-weight organic matters such as humic acids, on the aerated IME process. A proper addition of H2O2 in the aerated IME can promote the corrosion of solid iron (Fe2+/Fe3+) and cause a likely domino effect in the enhancement of removal efficiencies.

Experimental study and thermodynamic calculations of phase relations in the Fe–C system at high pressure

We have conducted a series of melting experiments in the Fe–C system at pressures up to 25 GPa in the temperature range of 1473–2073 K. The results define the phase relations at several pressures, including the eutectic temperature and composition as a function of pressure, carbon partitioning between solid iron and liquid, and change of melting relations involving iron carbides. In order to interpolate and extrapolate the phase relations over a wide pressure and temperature range, we have established a comprehensive thermodynamic model in the Fe–C binary system. The calculated phase diagrams at pressures of 5, 10, and 20 GPa reproduce the experimental data, including the solubility of carbon in solid iron and the effect of pressure on the eutectic temperature and composition. The formation of Fe7C3 at pressures above 5 GPa is correctly modeled and the change of phase relations in the Fe–C system between 5 and 10 GPa is captured in the model. The model provides predictions of the phase relations at 136 GPa and 330 GPa, based on existing knowledge of the thermochemistry of the system at lower pressure. The calculated phase relations can be used to understand the role of carbon during inner core crystallization, predicting carbon distribution between the inner and outer cores and mineralogy of the solid inner core.

Technological tradition of the Mongol Empire as inferred from bloomery and cast iron objects excavated in Karakorum

Iron objects from Karakorum, the former capital of the Mongol Empire, were metallographically examined. Most were forged out of bloomery iron, particularly those requiring superior functional properties. By contrast, approximately one third were made from cast iron, with carbon levels approximating either cast iron or ultrahigh carbon steel. The carbon concentration of the bloomery products was controlled either by a carburization treatment directed at the functional parts or by the welding of a pre-carburized steel plate to a low carbon body. By comparison, cast iron-based steelmaking was achieved by subjecting pieces of solid cast iron to a combined thermal and mechanical treatment aimed at accelerating decarburization. Some anonymous cast objects were circulated as a feedstock for this unique process, naturally taking the form of thin plates. Also, the cast products examined were contaminated with substantial amounts of sulfur and silicon, suggesting that they originated from liquid iron smelted at relatively high temperatures using fossil fuel instead of charcoal. Given these findings, it can be concluded that the Mongol Empire took advantage of an effective multi-faceted iron tradition, which combined bloomery-based and cast iron-based iron technologies. It is important to note, however, that the former still remained the key technological tradition dominating the local contemporary iron industry.

Thermodynamics of boron distribution in solvent refining of silicon using ferrosilicon alloys

Distribution coefficient of boron between purified solid silicon and iron–silicon melt at infinite dilution of boron was evaluated to investigate the effectiveness of boron removal from silicon by solvent refining using iron. The estimated values for distribution coefficient of boron at infinite dilution are: 0.49±0.01 (1583K), 0.41±0.03 (1533K) and 0.33±0.04 (1483K). The distribution coefficient increases with temperature showing less boron removal at higher temperatures. The estimated values for self interaction parameter of boron are as follow: −96±12 (1583K), −111±28 (1533K) and −159±45 (1483K). Activity coefficient of boron in solid silicon was obtained and related to temperature as lnγBinsolidSi0=(16317±282)1T-(7.06±0.18).

Anisotropy of Earth's inner core intrinsic attenuation from seismic normal mode models

The Earth's inner core, the slowly growing sphere of solid iron alloy at the centre of our planet, is known to exhibit seismic anisotropy. Both normal mode and body wave studies have established that, when the global average is taken, compressional waves propagate faster in the North–South direction than in the equatorial plane. Recent body wave studies also indicate that this fast direction may be more attenuating, and interpret this anisotropic attenuation in terms of anisotropic scattering due to inner core texturing. Here we use the Earth's normal modes to study the attenuation anisotropy of both compressional and shear waves in the inner core. As normal modes have wavelengths several orders of magnitude longer than estimates of inner core grain size, any attenuation anisotropy quantified using normal modes must reflect the anisotropy of intrinsic (viscoelastic) attenuation of the crystalline inner core alloy. By inverting zonal anelastic and elastic normal mode splitting function coefficients of twenty inner core sensitive modes, we construct models of inner core intrinsic attenuation and velocity anisotropy. We find that, for compressional waves, the North–South direction is both fast and more strongly attenuating. The existence of intrinsic inner core attenuation anisotropy can be interpreted in terms of anisotropic Zener relaxation in the metallic alloy comprising the inner core. Such anisotropic Zener relaxation has only been observed in the presence of solute atoms, and is thus entirely consistent with the presence of a few atomic per cent of light elements in the Earth's inner core.

Magnet design for a low-emittance storage ring.

The MAX IV 3 GeV storage ring, currently under construction, pursues the goal of low electron beam emittance by using a multi-bend achromat magnet lattice, which is realised by having several consecutive magnet elements precision-machined out of a common solid iron block, 2.3-3.4 m long. With this magnet design solution, instead of having 1320 individual magnets, the MAX IV 3 GeV storage ring is built up using 140 integrated `magnet block' units, containing all these magnet elements. Major features of this magnet block design are compactness, vibration stability and that the alignment of magnet elements within each unit is given by the mechanical accuracy of the CNC machining rather than individual field measurement and adjustment. This article presents practical engineering details of implementing this magnet design solution, and mechanical + magnetic field measurement results from the magnet production series. At the time of writing (spring 2014), the production series, which is totally outsourced to industry, is roughly half way through, with mechanical/magnetic QA conforming to specifications. It is the conclusion of the authors that the MAX IV magnet block concept, which has sometimes been described as new or innovative, is from a manufacturing point of view simply a collection of known mature production methods and measurement procedures, which can be executed at fixed cost with a low level of risk.

Bioreduction of biotite and chlorite by a Shewanella species

The interactions between the Fe(III)-reducing bacterium Shewanella oneidensis MR-1 and the phyllosilicate minerals biotite and chlorite have been studied. In washed, non-growing cell suspensions, S. oneidensis MR-1 was able to mediate the reduction of Fe(III) in biotite and chlorite in the presence and absence of an artificial electron shuttle, and to reduce as much as 36% of the starting Fe(III) in biotite, and 21% in chlorite. This is predominantly a solid-state reaction, as no significant dissolution or change in morphology was observed after microbial reduction. In growing-cell experiments, with Fe(III) as the only electron acceptor, bacterial biomass increased over eight weeks of incubation. Combining the results of (weak acid-extractable) iron characterization by ferrozine assay and bulk solid iron mineral characterization using Mossbauer spectroscopy, has led to the development of a possible mechanism of reduction of Fe(III) in the bulk of the mineral. Long-distance electron transfer between M2 sites along octahedral layers may facilitate the reduction of the bulk mineral. To our knowledge, this is the first study to demonstrate microbially mediated reduction of Fe(III) within biotite, and show the ability of S. oneidensis MR-1 to conserve energy for growth from this reduction.

Enhancement of interfacial reaction between solid iron and molten tin by mechanical actions

The influences of mechanical actions on interfacial reactions between an iron plate and molten tin were examined. Tensile and compressive stresses up to 100 MPa on the iron plate did not significantly change the thickness of the reaction layer and the corrosion depth of the plate. However, when the iron plate was subjected to repeated rubbing with tungsten and Pb–Sn eutectic alloy wires and when it was immersed in the rotating molten tin, the reaction layer thickness decreased and the corrosion depth of the iron plate increased. From these results, it was concluded that the corrosion of the iron plate in the molten tin was enhanced by repeated rubbing with the solder alloy on the plated iron layer and also by flow of molten solder alloy down the surface of the soldering tip in the soldering process.

Simultaneous Spectrophotometric Determination of Iron (III) and Vanadium (V) in Water Samples Using a Combination of Partial Least Squares Regression and Solid Phase Extraction with Modified Octadecyl Silica Membrane Disks

In this work solid phase extraction had been implemented with fiber optic-linear array detection spectrometry and partial least squares (PLS) multivariate calibration approach for simultaneous determination of ultra trace amounts of metals with complexes which have overlapping spectra. An octadecyl silica membrane disk modified with N-benzoyl-Nphenylhydroxylamine (BPHA) in combination with partial least squares regression (PLS) was used for simultaneous preconcentration and spectrophotometric determination of iron and vanadium in water samples. The method was based on the retention of V(V) and Fe(III) on the disks modified by BPHA in the pH range of 2.0-4.5. The retained ions were eluted with 3 mL of methyl isobutyl ketone and were measured spectrophotometrically. The data obtained from the experiments were processed by partial least squares chemometric method. PLS was applied for multivariate calibration and noise reduction through eliminating of the less important latent variables. Under the optimum conditions, for preconcentrating the analytes from 100 mL sample, the linear dynamic ranges were 14–320 µg L-1 and 10–530 µg L-1 and the detection limits were 4.2 µg L-1 and 2.5 µg L-1 for V(V) and Fe(III), respectively. The method was successfully applied to the determination of analytes in several categories of water samples. The accuracy was assessed through the recovery experiments, independent analysis by graphite furnace atomic absorption spectrometry and the analysis of a certified reference water sample. Keywords: Solid phase extraction, chemometrics, spectrophotometry, iron (III) and vanadium (V) determination.

Mucormycosis with diabetic and lupus nephropathy.

A 67-year-old woman with Stage 3 chronic kidney disease (CKD) due to systemic lupus erythematous (SLE). She was admitted to our hospital with a diagnosis of acute kidney injury. She had a past medical history of hypertension, acanthosis nigricans, obesity, obstructive sleep apnoea and type 2 diabetes mellitus with diabetic retinopathy. Two months prior to admission she had presented with a deterioration in renal function with proteinuria, which was interpreted as a flare of her SLE and she had received treatment with cyclophosphamide and i.v. 6-methylprednisolone. Five days after admission she presented with dyspnoea with bilateral pulmonary infiltrates. A diagnosis of heart failure was made and she underwent ultrafiltration with slight improvement. On the 10th day after admission she developed a right third cranial nerve palsy. A brain CT scan and lumbar puncture were normal except for the findings suggestive of chronic maxillary sinusitis. Fibrobronchoscopy showed necrosis of the nasal septum and infection due to Mucor genera was suspected. She underwent surgical debridement and initiated treatment with amphotericin B and caspofungin and was admitted to the ICU for respiratory support. The patient deteriorated despite treatment and died on her fourth day in the ICU. Rhizopus spp was identified in the oral cavity biopsies (Figure 1). Fig. 1. Necrosis of the oral cavity due to Rhizopus (green arrows). As the number of immunocompromised patients increase, the frequency of mucormycosis [1] is increasing. Mucormycosis, also known as zygomycosis, is an opportunistic fungal infection caused by organisms of the mucorales order. The most frequent species are Rhizopus, Mucor and Rhizomucor (Figure 2). Fig. 2. Rhizopus in oral cavity biopsy (green arrows). Haematoxylin and eosin stain. Risk factors [2] for these infections include diabetes mellitus (especially in patients with ketoacidosis), haematologic malignancies, haematopoietic stem cell transplantation, solid organ transplantation, deferoxamine treatment and iron overload (Figure 3). Fig. 3. Rhizopus in oral cavity biopsy (green arrow). Grocott's Methenamine Silver stain. Mucormycosis may present with rhino-orbital-cerebral (which is the most common), pulmonary, gastrointestinal, cutaneous, renal and disseminated involvement [3]. The diagnosis is based on identification of organisms in the tissue by histopathology with confirmation by culture. Treatment is based on a combination of surgical debridement with long-term amphotericin B therapy. Owing to the aggressive course of mucormycosis, even with treatment, many other treatments [4] have been considered such caspofungin (for rhino-orbital-cerebral disease), long-term posaconazol (as a step-down therapy) and deferasirox. The prognosis is poor in all the presentations with mortality rates as high as 87% with pulmonary involvement.

Iron Composite Anodes for Fabricating All-Solid-State Iron-Air Rechargeable Batteries

Hydroxide ion conductors containing KOH were prepared for application in an all-solid-state Fe–air battery. ZrO2 and Mg–Al layered double hydroxide (LDH) were employed as the matrix materials. The ionic conductivity and conducting ion species were evaluated by impedance and electromotive force measurements. Repeated charge and discharge were achieved by using negative electrodes composed of the solid electrolyte and iron oxide-supported carbon.