Synthetic Iron Research Articles

Highly regioselective oxidation of C-H bonds in water using hydrogen peroxide by a cytochrome P450 mimicking iron complex.

Cytochrome P450, one of nature's oxidative workhorses, catalyzes the oxidation of C-H bonds in complex biological settings. Extensive research has been conducted over the past five decades to develop a fully functional mimic that activates O2 or H2O2 in water to oxidize strong C-H bonds. We report the first example of a synthetic iron complex that functionally mimics cytochrome P450 in 100% water using H2O2 as the oxidant. This iron complex, in which one methyl group is replaced with a phenyl group in either wing of the macrocycle, oxidized unactivated C-H bonds in small organic molecules with very high selectivity in water (pH 8.5). Several substrates (34 examples) that contained arenes, heteroaromatics, and polar functional groups were oxidized with predictable selectivity and stereoretention with moderate to high yields (50-90%), low catalyst loadings (1-4 mol%) and a small excess of H2O2 (2-3 equiv.) in water. Mechanistic studies indicated the oxoiron(v) to be the active intermediate in water and displayed unprecedented selectivity towards 3° C-H bonds. Under single-turnover conditions, the reactivity of this oxoiron(v) intermediate in water was found to be around 300 fold higher than that in CH3CN, thus implying the role water plays in enzymatic systems.

Enhanced bioremediation of cyclohexaneacetic acid in offshore sediments with green synthetic iron oxide and Pseudoalteromonas sp.

Naphthenic acids (NAs) have been found to exert serious threats on offshore sediment ecosystems and human health in recent years, which entails us the urgent need for NAs remediation. Bioremediation is considered an ideal method for sediment remediation due to ecological sustainability and economic feasibility. However, current bioremediation efficiency of offshore sediments suffers from relatively slow and there has never any attempts to bioremediate offshore sediment NAs contamination hitherto. In this study, the green synthetic iron oxides (gFeOx) based on Laminaria extracts was employed to enhance the biodegradation of NAs (Cyclohexylacetic acid, CHAA) in offshore sediments by Pseudoalteromonas sp. JSTW (an indigenous microorganism). The results showed that CHAA (20mg·kg-1) in offshore sediments was removed almost 100% within 7days at 30mg·kg-1 gFeOx and 0.6mg·kg-1 Strain JSTW. High-throughput sequencing results revealed that the structure and function of sediment microbial community were essentially restored to uncontaminated levels after bioremediation, highlighting the joint remediation approach is an efficient and eco-friendly method. Overall, this work has firstly provided insights into the application for NAs in situ bioremediation in offshore sediments.

Characterization of a Proposed Terminal Iron(III) Nitride Intermediate of Nitrogen Fixation Stabilized by a Trisphosphine‐Borane Ligand

AbstractTerminal iron nitrides (Fe≡N) have been proposed as intermediates of Fe‐mediated nitrogen fixation, and well‐defined synthetic iron nitrides have been characterized in high oxidation states, including FeIV, FeV, and FeVI. This study reports the generation and low temperature characterization of a terminally bound iron(III) nitride, P3BFe(N) (P3B=tris(o‐diisopropylphosphinophenyl)borane), which is a proposed intermediate of iron‐mediated nitrogen fixation by the P3BFe‐catalyst system. CW‐ and pulse EPR spectroscopy (HYSCORE and ENDOR), supported by DFT calculations, help to define a 2A ground state electronic structure of this C3‐symmetric nitride species, placing the unpaired spin in a sigma orbital along the B−Fe−N vector; this electronic structure is distinct for an iron nitride. The unusual d5‐configuration is stabilized by significant delocalization (≈50 %) of the unpaired electron onto the axial boron and nitrogen ligands, with a majority of the spin residing on boron.

Characterization of a Proposed Terminal Iron(III) Nitride Intermediate of Nitrogen Fixation Stabilized by a Trisphosphine-Borane Ligand.

Terminal iron nitrides (Fe≡N) have been proposed as intermediates of Fe-mediated nitrogen fixation, and well-defined synthetic iron nitrides have been characterized in high oxidation states, including FeIV , FeV , and FeVI . This study reports the generation and low temperature characterization of a terminally bound iron(III) nitride, P3 B Fe(N) (P3 B =tris(o-diisopropylphosphinophenyl)borane), which is a proposed intermediate of iron-mediated nitrogen fixation by the P3 B Fe-catalyst system. CW- and pulse EPR spectroscopy (HYSCORE and ENDOR), supported by DFT calculations, help to define a 2 A ground state electronic structure of this C3 -symmetric nitride species, placing the unpaired spin in a sigma orbital along the B-Fe-N vector; this electronic structure is distinct for an iron nitride. The unusual d5 -configuration is stabilized by significant delocalization (≈50 %) of the unpaired electron onto the axial boron and nitrogen ligands, with a majority of the spin residing on boron.

Influence of Moisture in Quartzite on the Lining Properties and Efficiency of Industrial-Frequency Induction Crucible Furnaces

The main purpose of industrial frequency induction crucible smelters (IGM) is the smelting of synthetic cast iron, using metal filling scrap in the amount of 30–35%, at a temperature not exceeding 1450 OZ C. The basis of the lining used is quartzite, which undergoes polymorphic transformations in the pre-treatment process to form tridimite. The efficiency of using these furnaces is significantly increased when using a metal casting consisting of a single steel scrap, but for this purpose, the melting mode has to be raised to 1550–1600 °C, which will reduce the resistance of the lining. The structural transformation of quartzite is strongly influenced by the state of water in it. In this work, studies have been carried out for changes in the water condition in the quartzite of the brand PCMVI-3 under the action of temperatures of 200–1550 °C. The Shimadzu XRF-1800 spectrometer established the actual chemical composition of the investigated quartzite and found that the amount of impurities in it is 0.66%. A derivative study of STA 449 F1 Jupiter found two endothermic effects. The first, at 170 °C, relates to the loss of adsorbed water. The second, at a temperature of 570 °C, passes without the loss of mass of the sample, and it is accompanied by the beginning of the process of the destruction of point defects in the form of Al-OH groupings. From a temperature of 620–630 °C, no mass changes associated with water removal were detected. The BRUKER D8 ADVANCE diffractometer investigated phase changes during the removal of moisture from the quartzite at temperatures of 200 and 800 °C and subsequent cooling and then during the heating used to sinter the lining. As a result, it has been established that the sheet in which the quartzite contains only chemically bound moisture, after sintering, turns into cristobalite and provides a more stable exposure to sudden temperature changes. This makes it possible to use up to 90% of the steel scrap in metal filling, which increases the efficiency of the melting furnace and the production of castings in general.

Green synthesis, characterization and antibacterial activity of iron oxide nanoparticles derived fromSolanum nigrum leaf extract

In order to create iron nanoparticles, extract from Solanum nigrum was used. By using UV/Vis absorptionspectroscopy, X-ray diffraction spectroscopy, and SEM examination, the produced iron nanoparticles were identified. Iron oxide nanoparticles exhibit a distinctive absorption peak in the UV/Vis spectrum between 200 and 300 nm. Theaverage particle size of magnetite nanoparticles, as determined by the X-ray diffraction method, was found to be 24.1nm. By using the well diffusion method, it was discovered that the synthetic iron nanoparticles have antibacterial action against harmful bacteria such Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, and Klebsiellapneumoniae. This biosynthetic method has been discovered to be economical, environmentally benign, and promisingfor use in a variety of fields. Keywords: Iron nanoparticles, Solanum nigrum, antibacterial activity

Increasing the Efficiency of Foundry Production by Changing the Technology of Pretreatment with Quartzite

The efficiency of the production of foundry products depends on the reliable operation of the melting furnace including, therefore, the durability of its lining. The most common material adopted for the production of an acid furnace crucible lining is quartzite, in which during the pretreatment (heating to 800 °C followed by holding), a tridymite phase appears that maintains a constant volume at 840–1470 °C for a long time and provides high lining durability of 300–350 melts, but only when using melting temperature regimes not exceeding 1500 °C. However, the absence of iron scrap leads to the smelting of synthetic iron from only one steel scrap using higher melting temperatures (1550–1570 °C), which sharply reduces the lifetime of the lining to 220 melts. This work is devoted to research aimed at establishing technology for the pretreatment with the original quartzite, which ensures the formation of a phase state that successfully withstands elevated temperatures for a long time. The studies were carried out using a Bruker D8 ADVANCE diffractometer and a Shimadzu XRF-1800 X-ray wave-dispersive spectrometer. The work consisted of drying samples of the original quartzite at temperatures of 200 and 800 °C with subsequent exposure to temperatures of 200, 400, 600, 870, 1000, 1200, 1470 and 1550 °C. As a result, the conditions for pretreatment of quartzite were established, during which during its further use, a cristobalite phase can be obtained, which makes it possible manufacture a high-temperature lining that ensures its high durability. The introduction of this technology will ensure the efficiency of the production of foundry products for enterprises operating induction crucible furnaces at industrial frequency.

Natural iron ores for large-scale thermochemical hydrogen and energy storage

A stable energy supply will require balancing the fluctuations of renewable energy generation due to the transition to renewable energy sources. Intraday and seasonal storage systems are often limited to local geographical or infrastructural circumstances.This study experimentally verifies the application of inexpensive and abundant natural iron ores for energy storage with combined hydrogen and heat release. The incorporated iron oxides are reduced with hydrogen from electrolysis to store energy in chemically bonded form. The on–demand reoxidation releases either pure hydrogen or high-temperature heat as valuable products. Natural iron ores as storage material are beneficial as the specific costs are lower by an order of magnitude compared to synthetic iron oxide-based materials.Suitable iron ores were tested in TG analysis and in a 1 kW fixed-bed reactor. Siderite, a carbonate iron ore, was verified as promising candidate, as it shows significantly lower reaction temperatures and twice the storage capacity over other commercial iron ores such as ilmenite. The specific storage costs are as low as 80–150 $ per MWh hydrogen stored, based on the experimental in-situ tests. The experimentally determined volumetric energy storage capacity for the bulk material was 1.7 and 1.8MWhm−3 for hydrogen and heat release, respectively. The raw siderite ore was stable for over 50 consecutive cycles at operating temperatures of 500–600 °C in in-situ lifetime tests.The combination of high abundance, low price and reasonable capacity can thus result in very low specific energy storage costs. The study proofs that suitable natural iron ores are an interesting economic solution for large-scale and seasonal energy storage systems.

De novo synthesis of ferrichrome by Fusarium oxysporum f. sp. cubense TR4 in response to iron starvation

Manipulation of iron bioavailability in the banana rhizosphere may suppress Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc). However, iron starvation induced by application of synthetic iron chelators does not effectively suppress Fusarium wilt. It is unclear whether Foc can subvert iron chelators and thereby evade iron starvation through the synthesis of iron-scavenging secondary metabolites, called siderophores. In vitro studies were conducted using iron-deficient growth medium and medium supplemented with a synthetic iron chelator, 2,2′-dipyridyl, to mimic iron starvation in Foc Tropical Race 4 (Foc TR4). Concentration of extracellular siderophores increased three-fold (p < 0.05) in the absence of iron. Liquid chromatography-mass spectrometry analysis detected the hydroxamate siderophore, ferrichrome, only in the mycelia of iron-starved cultures. Moreover, iron-starved cultures exhibited a reduction in total cellular protein concentration. In contrast, out of the 20 proteinogenic amino acids, only arginine increased (p < 0.05) under iron starvation. Our findings suggest that iron starvation does not cause a remodelling of amino acid metabolism in Foc TR4, except for arginine, which is required for biosynthesis of ornithine, the precursor for siderophore biosynthesis. Collectively, our findings suggest that biosynthesis of siderophores, particularly ferrichrome, could be a counteractive mechanism for Foc TR4 to evade iron starvation.

Understanding reactions between water and steelmaking slags: Iron distribution, hydrogen generation, and phase transformations

Environmentally friendly energy harvesting can be achieved by the H2O thermochemical treatment of steelmaking slags. Hot slag from steel manufacturing is used as a sacrificial material to produce H2 in a stream of steam. In parallel, this process enhances the magnetic properties of the slag, benefitting the Fe recovery. In this work, the occurrence states of different iron species in slags, as well as their reactivity and phase transformations in H2O, were investigated. The results showed that Fe2+ was mainly distributed in olivine (Ca, Fe, Mg, Mn)2SiO4 when the basicity was low. As the basicity increased, a gradual enrichment of Fe2+ in RO phase (divalent oxides solid solution, R = Fe, Mg, Mn etc.) was observed. In addition to steelmaking slags, the H2O splitting reactions of synthetic model iron compounds, RO phase (Mg1–xFexO, x = 0.36, 0.63, 0.77) and kirschsteinite (CaFeSiO4) were also tested. RO phase exhibited fast kinetics, with its activity proportional to the FeO content. Oxidation of the magnesia-rich RO phase resulted in the phase segregation of iron-depleted magnesiowüstite (Mg,Fedepleted)O and iron-rich spinel (Mg,Ferich)3O4. The H2O splitting of CaFeSiO4 suffered from extremely low kinetics below 900 °C, which could be enhanced by raising the temperature. The H2 production capacity of steelmaking slags was strongly affected by the basicity, which improved when more Fe2+ existed as RO phase rather than CaFeSiO4. After oxidation in steam at 850 °C, the slag sample with a basicity of 1.83 produced 29.3 cm3⋅g−1material hydrogen at 850 °C for 60 min, with a conversion ratio of 80.1%.

Second Sphere Effects on Oxygen Reduction and Peroxide Activation by Mononuclear Iron Porphyrins and Related Systems.

Activation and reduction of O2 and H2O2 by synthetic and biosynthetic iron porphyrin models have proved to be a versatile platform for evaluating second-sphere effects deemed important in naturally occurring heme active sites. Advances in synthetic techniques have made it possible to install different functional groups around the porphyrin ligand, recreating artificial analogues of the proximal and distal sites encountered in the heme proteins. Using judicious choices of these substituents, several of the elegant second-sphere effects that are proposed to be important in the reactivity of key heme proteins have been evaluated under controlled environments, adding fundamental insight into the roles played by these weak interactions in nature. This review presents a detailed description of these efforts and how these have not only demystified these second-sphere effects but also how the knowledge obtained resulted in functional mimics of these heme enzymes.

LANXESS Offers EPDs for Synthetic Iron Oxide Pigments

LANXESS Offers EPDs for Synthetic Iron Oxide Pigments

Fenton-Mediated Chlorophenol Degradation by Iron-Reducing Compounds Isolated from Endophytic Fungi in Atacama Puna Plateau Lecanicillium ATA01

Low-molecular-mass iron-reducing compounds (IRCs) were produced by entomopathogenic endophytic fungi Lecanicillium sp. ATA01 in liquid cultures. The extracellular hydrophilic extract contained three IRCs formed by peptides, iron and phenolate structures with molecular masses of 1207, 567 and 550 Da. These compounds were able to chelate and mediate the reduction of Fe+3 to Fe+2 and oxidized recalcitrant lignin-model substrates such as veratryl alcohol (VA), 2,6-dimethoxyphenol (DMP), and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) with or without hydrogen peroxide. Besides, IRCs can promote the degradation of chlorophenols. The maximal degradation of p-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol was conducted at optimal degradation conditions for IRCs (pH 3.5, iron 100 mM, and H2O2 10 mM). Furthermore, Fenton-like reactions using the synthetic iron chelates DTPA and EDTA and free Fe+2 and Fe+3 were also carried out in order to compare with the reaction mediated by IRCs. The ferric IRCs displayed the ability to enhance the hydroxylation of chlorophenols as a part of a degradation mechanism of the IRC-assisted Fenton reaction. The complexed iron was more efficient than free iron in the Fenton-like reaction, and between them, the fungal chelates were more efficient than the synthetic mill chelates.

Features of cast iron for railway brake pads

Thepaperpresentstheresultsof comparison of quality indices of brake shoes for railroad rolling stock made of synthetic cast iron smelted in induction furnaces and of composite material which is a vulcanized mixture of rubber and different fillers. Disclosed are the disadvantages of composite brake pads. Defects of the working surface of the railway rolling stock wheels rolling surface caused by the application of composite brake pads made of rubber-asbestos or rubber-asbestos mixture are shown. Parameters of C, Si, Mn, P, S content and carbon equivalent distribution in cast iron used for the production of «M» type brake shoes according to GOST 30249-97 are analysed. It is established that the hardness and fracture strength of pads do not correlate with the content of chemical elements in cast iron and its carbon equivalent. The ranges of C, Si, Mn, P, S distributions in the specified purpose cast iron are much narrower than the allowable limits of these elements specified in GOST 30249–97. Suggestions for improving the standards are given.

Визначення вуглецевого еквівалента і ступеня евтектичності чавуну в ливарному виробництві

The issues related to the essence of the concepts of carbon equivalent, an indicator of the degree of eutecticity and the ratio of carbon content to silicon content for characterizing the chemical composition and properties of gray cast iron were analyzed. The results of studies of the carbon equivalent value, the degree of eutecticity and the C/Si ratio of the chemical composition of synthetic cast iron, which is used for the manufacture of brake pads and the «Khanin wedge» of railway rolling stock, are presented. Examples of different approaches and formulas for determining the limits and methods of using the carbon equivalent of the chemical composition of cast iron to characterize the weldability of steels, coefficient of friction, wear, other operational indicators of cast iron brake pads, and evaluation of the quality of cast iron as a whole are given and analyzed. Within the standards-regulated ranges of the content of chemical elements in cast iron, the value of its carbon equivalent in individual smelting batches of products can differ significantly (by 30 %). With certain ratios of the main elements in the chemical composition of cast iron, the values of the carbon equivalent can be the same, but the mechanisms of crystallization of cast iron and its properties do not coincide. The parameters of the distribution of the content of carbon, silicon, manganese, phosphorus, sulfur, carbon equivalent, and the degree of eutecticity in cast iron СЧ350, from which the friction «Khanin wedge» for railway rolling stock is made, were analyzed. Cleaning the factory arrays of indicators of chemical composition, hardness, carbon equivalent, degree of eutecticity of cast irons intended for the production of brake pads and the friction «Khanin wedge» from gross erroneous values practically did not affect the general characteristics of the statistical analysis, which indicates the reliability of the results. It is shown that when smelting in induction crucible furnaces gray synthetic cast iron intended for the production of brake pads and the «Khanin wedge», the ranges of variation in the content of C, Si, Mn, P, S are much narrower than those regulated by the standards for these foundry products. The fundamental possibility of introducing appropriate clarifications to the requirements of the standards regarding the content of chemical elements in synthetic gray cast iron intended for the production of brake pads of the «M» type and the friction «Khanin wedge» for railway rolling stock was noted, in particular, reducing the sulfur content to 0,05 % to increase stability of its quality. Keywords: cast iron, chemical composition, carbon equivalent, degree of eutecticity, properties, castings, brake pads, operational characteristics.

The Phragmites Root-Inhabiting Microbiome: A Critical Review on Its Composition and Environmental Application

As widespread wetland plants, Phragmites play a vital role in water purification and are widely utilized in constructed wetlands (accounting for 15.5% of applied wetland plants) as a natural alternative to wastewater treatment. However, despite such common applications, current understanding of the basic composition of the Phragmites root-inhabiting microbiome and the complex functions of each member of this microbiome remains incomplete, especially regarding pollution remediation. This review summarizes the advances that have been made in ecological and biochemical research on the Phragmites root microbiome, including bacteria, archaea, and fungi. Based on next-generation sequencing, microbial community compositions have been profiled under various environmental conditions. Furthermore, culture-based methods have helped to clarify the functions of the microbiome, such as metal iron stabilization, organic matter degradation, and nutrient element transformation. The unique community structure and functions are highly impacted by Phragmites lineages and environmental factors such as salinity. Based on the current understanding of the Phragmites root microbiome, we propose that synthetic microbial communities and iron–manganese plaque could be applied and intensified in constructed wetlands to help promote their water purification performance.

Determining the inherent selectivity for carbon radical hydroxylation versus halogenation with high-spin oxoiron(iv)-halide complexes: a concerted rebound step.

A synthetic iron model can process both halogenation and hydroxylation with vague selectivity, which is different from halogenase even though these structures are used for the simulation of halogenase. The key factor of the synthetic oxo-iron model mediated hydroxylation or the halogenation is still under debate. Herein density functional theory calculation is used to investigate the hydroxylation versus halogenation of propylene by the complex [FeIV(O)(TQA)(X)]+ (X = F, Cl, Br). Our results suggest that a concerted rebound mechanism (between the -X and the hydroxyl ligands after the hydrogen abstraction) leads to the formation of two different kinds of products.

In vitro Assessment of Solar Filters for Erythropoietic Protoporphyria in the Action Spectrum of Protoporphyrin IX.

Introduction: Subjects with erythropoietic protoporphyria rely on broad-spectrum sunscreens with high sun protection factor, which is not informative on efficacy in the absorption spectrum of protoporphyrin IX, spanning visible radiation and peaking around 408 nm. Photoactivation of protoporphyrin IX is responsible for painful skin photosensitivity in erythropoietic protoporphyria.The authors assessed the protective efficacy of six sunscreens in vitro in the absorption spectrum of protoporphyrin IX.Method: Transmittance measurements were performed in the 300–850 nm wavelengths on samples of six photoprotective products applied to polymethyl methacrylate plates. Porphyrin protection factor was calculated in the 300–700 nm region to provide a measurement for the efficacy of each product based on the action spectrum of protoporphyrin IX.Results: Product A showed the highest porphyrin protection factor among tested products with a median value of 4.22. Product A is a sunscreen containing organic filters, titanium dioxide and synthetic iron oxides, pigmentary grade active ingredients that absorb visible radiation. Other products showed inefficient protection in the visible, with transmittance between 75 and 95% at 500 nm. The low porphyrin protection factor of inorganic filter product B was attributed to particle micronization, as declared by the manufacturer.Conclusion: Adding porphyrin protection factor to sunscreen labeling could help patients with erythropoietic protoporphyria and other photosensitivity disorders identify products tailored on their specific needs. The development of sunscreens providing protection from visible radiation and excellent cosmetical tolerability could improve the lifestyle of patients with erythropoietic protoporphyria.

Оцінка стабільності хімічного складу і механічних властивостей промислових партій синтетичного чавуну

Оцінка стабільності хімічного складу і механічних властивостей промислових партій синтетичного чавуну

Increasing the Efficiency of Production of Synthetic Cast Iron Castings

The main factor that determines the content of the development strategies of a modern foundry is the use of modern technological processes, especially melting technology. First of all, this applies to the production of iron castings, which make up 65% of the mass of all alloys. Since 2000, in Russia, there has been a sharp decrease in the amount of pig iron scrap, the cost of foundry and pig iron and the cost of their transportation have increased significantly. This led to an increase in material costs in the production of castings from synthetic iron, which was mainly obtained in crucible induction furnaces of industrial frequency (ICT). In addition, problems began to arise with the use of acidic lining as the cheapest and most durable, since an increased amount of steel scrap began to be used in the metal charge, and for this reason the melting temperature was raised above 1450 ° C. The durability of the lining has sharply decreased, and downtime associated with its replacement has increased. All this had a negative impact on the efficiency of the production of synthetic iron castings.