Produce Iron Oxide Research Articles

Оценка технико-экономической эффективности пирометаллургической технологии переработки пылей электросталеплавильного производства

An evaluation of technical and economic efficiency parameters of a previously proposed technological solution for processing dust from electric steel production by the pyrometallurgical method is presented. The technological approach consists in the reduction of iron and zinc from their oxygen-containing forms (ZnFe 2 O 4 and ZnO) by active carbon-containing materials. Experiments were carried out on samples with a 26.02 and 37.7%wt. of ZnO and Fe 2 O 3 , respectively, to evaluate the processing of industrial dust of PJSC Magnitogorsk Iron and Steel Works in a laboratory facility based on the LHT 08/17 high-temperature furnace (Nabertherm, Germany). "Small long-flame nut" brand charcoal was applied as a carbon reducing agent, with lime and quartz sand serving as sources of slag-forming components. Commercial products were obtained in the form of granular cast iron (96.75 and 2.92%wt. of Fe and C, respectively) and a zinc oxide product (90.21%wt. of ZnO). The extraction of iron and zinc in cast iron comprised the values of 94.0 and 91.0%, respectively. As a result, an annular hearth furnace is recommended as the main technological unit for the industrial implementation of the process. The basic technological scheme is proposed including dosing raw materials, preparing charge briquettes, performing reduction smelting, separation of smelting products (cast iron and slag) and trapping zinc-containing sublimates. To assess the technical and economic efficiency of the developed technology on an industrial scale, the costs of building a dust processing plant involving one annular furnace with an average diameter of 12 m having a steel production capacity of 15 000 tonnes per year were taken into account. The proposed technology was shown to be capable of supporting commercial granular cast iron and zinc oxide products in the amount of 33264 and 4435 tonnes per year, respectively. Considering the investment period, the estimated payback period is determined to be 34 months with the expected net profit equal to 535.59 million rubles/year.

A sustainable nanocomposite for removal of heavy metals from water based on crosslinked sodium alginate with iron oxide waste material from steel industry

Abstract Industrial activities with zero waste have been recently targeted for the sake of cleaner environment. Therefore, industrial wastes are recycled and reused in self-manufacturing processes or employed in other industrial sectors and applications. In this work, steel industrial waste material such as iron oxide fine powder was utilized to remove some heavy metal such as lead, cadmium and copper from water. Iron oxide waste was grinded to produce iron oxide waste nanoparticles (IOWNPs) and was crosslinked to alginate as a biodegradable polymer to produce IOWNPs-Alg nanocomposite. The nanocomposite structure was validated using FTIR, SEM, TEM, TGA and XRD. The equilibrium sorption was obtained after 30 min with maximum capacities for lead, copper and cadmium; 564 mg g−1, 158 mg g-1 and 102.2 mg g−1, respectively. Adsorption behaviors were investigated using five isotherm models. The pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham`s kinetic models were used for kinetic behavior evaluations. The adsorption kinetic study referred to satisfactory adsorption of cadmium via pseudo-first order, while pseudo-second order was the best model to describe adsorption of copper and lead ions onto IOWNPs-Alg nanocomposite. The adsorption behaviors of evaluated heavy metal ions were found to obey Freundlich isotherm model and confirm surface heterogeneity and exponential distribution of active sites. The assembled IOWNPs-Alg nanocomposite was further confirmed as an effective nanosorbent for removal of lead, cadmium and copper from wastewater samples.

Reuse of Waste Pickling Acid for the Production of Hydrochloric Acid Solution, Iron(II) Chloride and Magnetic Iron Oxide: An Eco-Friendly Process

In this work, a novel strategy based on evaporation and crystallization unit operations, capable of producing hydrochloric acid solution, iron(II) chloride and magnetic iron oxide from waste pickling acid (WPA), is proposed to be an eco-friendly alternative to the methods available in the literature. The suggested approach took into account both the partial recovery of the unused HCl by evaporation/condensation and iron(II) chloride by crystallization at room temperature. It was possible to obtain chemicals with yields above 80 wt% and purity above 97 wt%. Magnetic iron oxide presented magnetic saturation of 70.1 emu/g, magnetic retentivity of 4.3 emu/g and magnetic coercivity of 44.5 Oe, as well as an undetectable level of contamination by metals other than iron and agglomeration of its nanoparticles. The HCl solution presented less than 35 mg/L of iron and zinc. The evapo-crystallization method showed potential to be a mild form of treating WPA and generating three chemicals in the same process.

Hematite replacement and oxidative overprinting recorded in the 1.88 Ga Gunflint iron formation, Ontario, Canada

Abstract The 1.88 Ga Gunflint Formation in Ontario, Canada, has played a key role in the development of current models for the deposition of iron formations. The presence of hematite-rich iron formation intercalated with chert stromatolites containing purported cyanobacterial microfossils sparked the idea that biology was the principal driver of Fe2+ oxidation and iron deposition. However, despite the abundance of hematite in the Gunflint Formation, a primary depositional origin has not been established. Here we present evidence for the replacement of Fe-silicate granules by hematite in drill core intersecting the Gunflint Formation. Iron-oxide replacement proceeded inwards from granule boundaries and along intergranular fractures, producing iron oxide–rich rims around Fe-silicate cores. The abundance of organic matter in shaly iron formation implies that the iron-rich mudstones experienced anoxic diagenesis and that coexisting hematite was not depositional but formed after burial. Widespread distribution of the alteration textures indicates that this was a large-scale process and that much of the hematite is not primary. Lifting the veil of oxidative overprinting reveals an iron-rich sediment that was originally more reduced and dominated by Fe(II)-rich minerals. Our results imply that a major assumption underpinning the original model for biological iron oxidation as the driver of iron formation deposition may be flawed, raising broader questions about the origin of hematite in other iron formations and the role of biology in iron deposition in the early oceans.

A Study of Iron Oxide Nanoparticles Synthesis by Using Bacteria

The biosynthesis of nanoparticles by using microorganisms is developing as an ecofriendly method for nanoparticle synthesis because of its cheap, simple and non-toxic. Bacillus sp. can be used for producing iron oxide nanoparticles. In addition, it has the ability for the biosynthesis of Fe3O4 nanoparticles. The nanoparticles producing was evaluated by using ultra violate-visible (UV-visible) and Fourier-transform infrared spectroscopy (FT-IR) methods also the production and size of the nanoparticle was confirmed by X-ray Diffraction and Field Emission Scanning Electron Microscope (FESEM) to confirm the accuracy of iron oxide nanoparticles. pH, Temperature, and Incubation time of production of iron oxide nano-particle also studied.

Iron and silicon oxide doped/PAN-based carbon nanofibers as free-standing anode material for Li-ion batteries

The advanced rechargeable batteries have been upgraded by the production of free-standing electrodes through electrospinning technology. This study aimed to introduce a novel hybrid composition to design a free-standing carbon nanofiber (CNF) based anode by the addition of iron acetylacetonate Fe(AcAc)3 as active material and TEOS(tetraethoxysilane)/APTES(aminopropyl triethoxysilane) as an additive for Li-ion batteries. Polyacrylonitrile(PAN) was used as the polymer matrix in the spin dope, and the inclusion of Fe(AcAc)3 and TEOS/APTES resulted in compositional change, producing iron oxide and silica nanoparticles throughout the matrix. Different oxidation states and the presence of embedded iron oxide nanoparticles in CNF were identified by XPS and EDX elemental mapping analysis. PAN-TEOS-APTES-Fe(AcAc)3 based anode material was capable of enhancing the reversible specific capacity as much as 732 mAhg−1 at 500 mAg−1 lasting for 300 cycles, along with the rate capability as high as 815 mAhg−1 at 200 mAg−1. Furthermore, EIS analysis and EX-situ FESEM showed decreased impedance after cycling with the stable morphology of PAN-TEOS-APTES-Fe(AcAc)3 CNF-film. Conclusively, non-woven, binder-free, current collector free, free-standing CNF anode film doped with iron-oxide and silica nanoparticles was indeed a novel approach for Li-ion batteries and can be considered for other batteries particularly for Li-S batteries.

Magnetic Biocatalysts of Pectinase: Synthesis by Macromolecular Cross-Linker for Application in Apple Juice Clarification

SUMMARYResearch backgroundPectinase enzyme has become a valuable compound in beverage industry. One of the most significant concepts to overcome the drawbacks of using industrial enzymes is their immobilization. In the present study, magnetic chitosan microparticles were utilized as a substrate for pectinase immobilization. New methods of enzyme immobilization involve the use of non-chemical cross-linkers between the enzyme and the substrate. The aim of this study is to immobilize the pectinase enzyme using polyaldehyde kefiran as a macromolecular cross-linker on magnetic particles.Experimental approachPectinase was immobilized in four steps: relative oxidation of kefiran and its application as a cross-linker, production of magnetic iron(II) iron(III) oxide (Fe3O4) microparticles, coating of magnetic Fe3O4 microparticles with chitosan, and immobilization of the enzyme on the substrate, prepared by the use of oxidized kefiran cross-linker. Parameters such as cross-linking concentration, time and ratio of chitosan magnetic microparticles to enzyme were optimized. Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering, transmission electron microscopy, and vibrating sample magnetometer were used to identify the groups and investigate the structures. The biochemical properties (stability of enzyme activity at different pH, temperature and time), enzyme reusability, kinetic parameters (Km and νmax) and apple juice turbidity, using free and immobilized pectinase enzymes, were also measured.Results and conclusionsCross-linker concentration, cross-linking time and the ratio of magnetic Fe3O4 microparticles with chitosan to enzyme were important factors in activity recovery of pectinase. FTIR analysis correctly identified functional groups in the structures. The results showed that after enzyme stabilization, the particle size and molecular mass, respectively, increased and decreased the magnetic saturation strength. According to the thermal kinetic study, the activity of the immobilized pectinase was higher than of its free form. The findings of this study indicate excellent stability and durability of the immobilized pectinase. Finally, a magnetic pectinase micro-biocatalyst was used to clarify apple juice, which reduced turbidity during processing.Novelty and scientific contributionThis study investigates the usage of kefiran oxidized as a new cross-linker for the immobilization of pectinase enzyme. Magnetic pectinase micro-biocatalyst has a good potential for industrial applications in the food industry, with high thermal stability.

The Oils Refining Process and Contaminants in Edible Oils: A Review

Edible oils are widely consumed foods. These oils come from various animal materials raw and vegetable products. Edible oils are prone to many contaminants. Contaminants can be found at all levels from oilseed production to conservation through refining processes and end up in oils. The contaminants origin may be of endogenous or exogenous. These are water, phosphorus, non-visible insoluble compounds, free fatty acids, residual hexane, benzo [a] pyrene, pesticides, dioxins, mycotoxins, mineral oils, cargo residues, minerals such as iron, copper, lead, gossypol, many primary and secondary oxidation products, etc. To eliminate or limit these compounds having a nuisance or toxicity for the consumer, it is allowed the refining of oils (chemical, physical or enzymatic). In addition, the regulatory limits of anti-nutritional factors in edible oils have been set in order to obtain quality oils and to guarantee the health of consumer living in developing country. This results in analytical methods developed for quantitative and qualitative evaluation of oils intended for human consumption.

Influence of heat treatment of iron oxide on its effectiveness as anticorrosion pigment in epoxy based coatings

Iron oxide powder was successfully synthesized by chemical precipitation method at room temperature, and annealed for 6 h, at 200, 500 and 900 °C. The obtained products were used as pigments in epoxy polyamide anticorrosive paint for iron steel substrate. The scanning electron microscopy analysis (SEM) and N2-sorption measurements shows a wire-like morphology and macroporosity for iron oxides annealed at 200 and 500 °C, and high-crystallinity and microporosityfor that treated at 900 °C. The WDS-XRF fluorescence indicates non-stochiometric structures. The X-ray diffraction (DRX) reveals well crystalline hematite solid phase α-Fe2O3 for materials annealed at 500 and 900 °C, and an almost amorphous structure for that treated at 200 °C, in agreement with the DSC analysis. The average crystallite size of the product heat treated at 900 °C (51.80 nm) is ∼1.8 times greater than the one treated at 500 °C (28.71 nm). The reflectance spectroscopy (RS) indicates bandgap values of ∼1.96 eV for both iron-oxide specimens treated at 200, 500 °C, and ∼ 1.37 eV for that treated at 900 °C, in agreement with the CIELab L*a*b*technique. The Brunauer–Emmett–Teller (BET) methodshows an inverse relationship between specific surface area versus the heat treatment temperature.The particle-size analysis (PSDA) indicate polydisperse particles. The wettability measurement reveals hydrophilic surfaces (θ < 90 °C), and a remarkable inversely proportional relationship between viscosity and annealing temperature; the lowest viscosity was obtained for the epoxy resin with embedded iron oxide product heat-treated at 900 °C. Both of the electrochemical impedance spectroscopy (EIS), over a frequency range of (1 mHz-100 kHz) and the optical microscopy show the best anticorrosion protection and efficiency for the epoxy resin paint incorporated by iron oxide pigment annealed at 500 °C.

A sustainable process for recovery of potash fertilizer from glauconite through simultaneous production of pigment grade red oxide

A sustainable process is proposed and developed for the recovery of potash fertilizer from glauconitic clay with simultaneous production of pigment grade iron oxide. Potassium is a part of stable structure (dioctahedral T-O-T) in glauconite and locked in alumino-silicate matrix. In order to break this matrix and maximize potassium dissolution, the glauconite sample containing 5.6% K2O and 31.9% Fe2O3 was subjected to reduction with coke followed by oxidation cooling (redox roasting). The process simultaneously releases potash and convert iron in the matrix to ferric state. The redox roasted sample was leached in hydrochloric acid and the leach liquor containing 6.1 g/L of potassium and 30.2 g/L of iron was subjected to solvent extraction using mixed solvent system (20% Aliquat 336 and 15% TBP) to separate iron prior to recovery of potash. Based on McCabe–Thiele plot, two stage counter current extraction at O:A ratio of 1:0.75 and three stage stripping at O:A ratio of 0.4:1 are sufficient to remove >99% of iron from the leach solution. The strip solution was hydrothermally treated to produce red iron oxide suitable for pigment application and iron free raffinate was treated to produce fertilizer grade potassium chloride.

Chromium (VI) removal using cerium doped iron oxide nanoparticles

The presence of high concentrations of hexavalent chromium in effluents is extremely harmful to the environment. To solve this environmental problem, several chemical treatments are applied in order to reduce the concentration of these ions in aqueous solutions, generally involving the reduction of Cr (VI) to Cr (III). Adsorption is a simple, efficient and economical method for the removal of contaminants, when a low-cost adsorbent is used. In this work, particles of cerium-doped iron oxides with different stoichiometric ratios were produced, with the adsorption capacity being evaluated by the removal of hexavalent chromium present in aqueous solution. Doping with cerium produced iron oxides with high surface area and certain textural characteristics, which favored the ability to remove chromium from aqueous solutions with a mechanism that combines adsorption and photoreduction of Cr (VI).

Production of iron oxide and nickel oxide nanostructural particles, investigation of the supercapacitor and photocatalytic properties

Abstract 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%.

A green chemistry to produce iron oxide – Chitosan nanocomposite (CS-IONC) for the upgraded bio-restorative and pharmacotherapeutic activities - Supra molecular nanoformulation against drug-resistant pathogens and malignant growth

The logical research on fundamentally adjusted iron oxide nanoparticles has turned out to expanded in biomedicine because of the improved activity and best biocompatibility. In this present work upgraded bio-restorative and pharmacotherapeutic property of chitosan‑iron oxide nanocomposite, which was set up by eco-friendly in situ substance technique. Characterisation of the synthesised nanocomposite by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction,(XRD) and Vibrating test magnetometer (VSM) studies reveals that highly stable spherical, electron-dense core shelled rough particles of 50-60 nm. Particle morphology of the synthesised nanocomposite utilising scanning electron microscopy (SEM) uncovers spherical; thick electron centre shelled harsh particles with the size scope of 50-60 nm. FTIR studies show that the specific interaction of practical gatherings of chitosan with iron oxide nanoparticles. Crystalline phase and magnetisation impact of the composite resolved from XRD and VSM studies. Anti-bacterial activity of the nanocomposite examined against human bacterial pathogens which suggest that the readied nanocomposite successfully restrained the development of the tried bacterial strains by recording maximum zone of inhibition, least minimum inhibition concentration (MIC) and biofilm damage against the both tested strains. 100 μg dosages of nanocomposites recorded 20.0 and 21.0 mm of the zone of inhibition against E. coli and S. aureus respectively. Biofilm restraint was additionally observed to be high in nanocomposite treatment by recording lower optical density of ethanol solubilised biofilm of both tested strains. Anticancer activity was examined against the A549 cell line by the assurance of cell feasibility as opposed to oxidative proteins, articulation example of TNF-α, Bax, PARP qualities and apoptosis. Composite prompted 50% of cytotoxicity at 80 μg/mL unmistakably uncovers cytotoxicity against A549 cells. Nanocomposite treatment revealed a high decrease of cell feasibility at all the fixation and most extreme impact seen in 100 μg. Nanocomposite treated cells demonstrated striking changes in cell morphology, the build-up of atomic material related to trademark changes in against oxidative enzymes, quality articulation design which brought about apoptosis-like necrotic cell death. The present findings would propose the conceivable usage of chitosan‑iron oxide nanocomposite as a viable remedial against safe medication pathogens and malignant growth cells.

Optimization of the Production Parameters of Composites from Sugarcane Bagasse and Iron Salts for Use in Dye Adsorption.

In this study, mechanical mixtures of sugarcane bagasse and iron salts (nitrate, acetate, or a mixture of both) were subjected to thermal decomposition for producing iron oxide and carbonaceous composite materials, which were evaluated as adsorbents for removing dyes from water using methylene blue (MB) as a model system. Aiming to optimize the conditions for obtaining composite adsorbents, the Box-Behnken design (BBD) was used to study the effects of mass sugarcane bagasse/mass iron salt, type of mixture of sugarcane bagasse/iron salt, and temperature on the response to be obtained (adsorption capacity, qe) before the execution of the adsorption tests. The synthesized composites were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. The relationship between the characteristics of different materials, based on the processing of statistical data and the results of the adsorption tests, helped determine the routes that led to formation of composites with the most suitable properties for the removal of MB dye. Different phases, such as magnetite (Fe3O4) and/or maghemite (γ-Fe2O3) and iron carbide (Fe3C), were formed. The composites that presented the highest qe values were SB/IN 1:1 (600°C) and SB/IN-IA 1:2 (400°C). The first, which contained iron carbide (Fe3C), according to the XRD results, also showed larger BET surface area than the other composites. These properties may have contributed to the higher MB adsorption efficiency of this material in aqueous medium. The sample SB/IN-IA 1:2 (400°C) had lower specific area and was composed of magnetite and/or maghemite phases. In this case, the high qe was probably associated with the surface properties promoted by combination with the carbonaceous material, favoring interactions with MB.

SYNTHESIS OF IRON OXIDE FROM METAL POWDERS

A comparative analysis of various methods for obtaining highly dispersed iron oxides has been carried out. The advantages and disadvantages of traditional and developing methods of synthesis of iron oxides for catalysts, sorbents and ceramic materials are identified. The advantages of the method of mechanochemical synthesis of obtaining highly dispersed iron oxides for catalysts for the medium-temperature conversion of CO in the production of ammonia and the oxidation of methanol to formaldehyde are shown. The methods of X-ray phase, X-ray structural, synchronous thermal analysis and Mössbauer spectroscopy were used to study the process of mechanochemical oxidation of iron and cast iron powders in order to obtain iron oxides. The phase composition and specific surface area of the obtained oxides are investigated. It was found that in the process of mechanical activation of iron-containing powders in the aquatic environment, the system Fe-Fe3O4-FeOOH is formed. Heat treatment at 450 °C for 6 h causes decomposition of FeOOH to α-Fe2O3 and partial oxidation of metallic iron. By the method of differential dissolution, it was established that the cast iron in the presence of water in a roller-ring vibratory mill for 60 min is oxidized to 77.6%, and the iron is oxidized to 88%. Also in the process of dissolving metal powders in oxalic acid solutions using ultrasound FeC2O4 · 2H2O is formed, which under the conditions of thermolysis decomposes to maghemite – γ-Fe2O3 with the release of CO and CO2, and at 400 °C to hematite – α-Fe2O3. The possibility of using the produced iron oxides for obtaining iron-chromium catalysts for the medium-temperature conversion of CO in the production of ammonia and iron-molybdenum catalysts for formaldehyde synthesis is shown. The CO degree conversion is 92.0% at 340 °C, and the productivity by formaldehyde is 13.0 µmol/(g∙s).

Temporal changes in magnetic signal of burnt soils – A compelling three years pilot study

Wildfires strongly affect soils, including iron biogeochemical cycling and carbon storage. Thus, it is important to reveal the dynamics of iron oxide synthesis and transformations during and after a wildfire. This study investigates the temporal stability of strongly magnetic minerals appearing after a wildfire. Following a designed experimental fire, samples from vegetation ash and mineral soil were taken immediately after and at progressively longer time intervals. The magnetic susceptibility monitoring of samples during three years period demonstrates an initial increase in magnetic signal of ash-rich material taken immediately after the fire followed by a gradual decrease over time. The behavior of samples collected later after the fire showed only a moderate decrease. It is suggested that the magnetic susceptibility rise during the laboratory storage could be due to the increased availability of nutrients and microbial activity immediately after the fire and related intense redox reactions involving iron oxide particles. The decreasing trend in magnetic susceptibility is ascribed to the oxidation of ultrafine magnetite particles with time. All mineral soil samples from the deeper level showed an initial susceptibility increase, assigned to a similar process. Magnetic susceptibility monitoring was also carried out on samples gathered shortly after natural wildfires. The soil samples affected by strong and long wildfires show a decrease in magnetic susceptibility with time. This effect is more pronounced in the surface black-colored ash layer. The ash material from a site disturbed by a strong short wildfire demonstrates behavior similar to the ash from the experimental fire. It is supposed that the temporal evolution of magnetic susceptibility of the mineral alteration products of wildfires is influenced by the grain size of the produced iron oxide particles, their redox reactions mediated by the heterotrophic bacteria, as well as the amplifying role of pyrogenic carbon for intensification of the redox reactions.

The Effects of 4%Fe on the Performance of Pure Zinc as Biodegradable Implant Material.

The efforts to develop structural materials for biodegradable metal implants have lately shifted their focus from Magnesium and Iron base alloys towards Zinc. This was mainly due to the accelerated corrosion rate of Mg that is accompanied by hydrogen gas evolution, formation of voluminous iron oxide products with reduced degradation rate in the case of Iron implants and the crucial role of Zn in many physiological processes. However the mechanical properties and degradation capabilities of pure zinc in physiological environment are limited and do not comply with the requirements of biodegradable implants. The present study aims at evaluating the effect of 4%Fe on the in-vitro and in-vivo behavior of pure Zinc. This was carried out in order to address the inherent disadvantages of pure zinc in terms of mechanical properties and biodegradability. The results obtained clearly indicate that the biocompatibility and mechanical properties of the new material system was in accord with the prospective requirements of biodegradable implants. However the corrosion degradation of the new alloy in in-vivo conditions was quite similar to that of pure zinc in spite of the significant micro-galvanic effect created by Delta phase Zn11Fe.

Removal of organic dye by biomass-based iron carbide composite with an improved stability and efficiency.

The efficiency of zero-valent iron (Fe0) for the degradation of contaminants in water or soil can be highly reduced by side reactions with oxygen or water. This work was conducted to test whether this drawback can be effectively suppressed by the carbonation of Fe0 with pyrolyzed biomass, which forms a Fe3C composite. The composite Fe3C was characterized and its reactivity and stability were assessed in batch tests with methyl orange (MO) as a model pollutant. The results indicated that the removal rate of MO on Fe3C composite was higher than that of Fe0 (7.587 mg/(g·min) vs. 4.306 mg/(g·min)) at pH 4, where the degradation mechanism was confirmed by high-performance liquid chromatography-mass spectrometry. More importantly, the produced iron oxide in the Fe3C composite was highly suppressed. Regeneration studies showed that after three times of cycling, the removal efficiency of MO on Fe3C composite was kept to 99.42%, but Fe0 almost lost its reactivity. In situ chemical reduction of a colorimetric redox probe (indigo-5, 5'-disulfonate, I2S) quantitatively demonstrated that Fe3C composite has the reduction kinetics of I2S obviously slower than Fe0, indicating that Fe3C composite improved the stability of incorporated Fe0 to resist the side oxidation.

Rapid and reversible lithiation of doped biogenous iron oxide nanoparticles

Certain bacteria produce iron oxide material assembled with nanoparticles (NPs) that are doped with silicon (Fe:Si ~ 3:1) in ambient environment. Such biogenous iron oxides (BIOX) proved to be an excellent electrode material for lithium-ion batteries, but underlying atomistic mechanisms remain elusive. Here, quantum molecular dynamics simulations, combined with biomimetic synthesis and characterization, show rapid charging and discharging of NP within 100 fs, with associated surface lithiation and delithiation, respectively. The rapid electric response of NP is due to the large fraction of surface atoms. Furthermore, this study reveals an essential role of Si-doping, which reduces the strength of Li-O bonds, thereby achieving more gentle and reversible lithiation culminating in enhanced cyclability of batteries. Combined with recent developments in bio-doping technologies, such fundamental understanding may lead to energy-efficient and environment-friendly synthesis of a wide variety of doped BIOX materials with customized properties.

Degradation analysis of mixed ionic-electronic conductor-supported iron-oxide oxygen carriers for chemical-looping conversion of methane

An iron-based oxygen carrier can convert natural gas into chemicals (syngas or hydrogen) with controlled CO2 emission in a redox process. Mixed ionic-electronic conductor (MIEC)-supported iron oxides have shown high catalytic activity by facilitating inward O anion diffusion. However, their durability has been tested under limited conditions, and key factors affecting the degradation of MIEC-supported iron oxides have rarely been identified. In this work, we find that the inherent redox stability and electronic conductivity of the support material are decisive properties that determine the redox stability and activity of iron oxide/MIEC composites, such as perovskite-type La0.8Sr0.2FeO3−δ and fluorite-type Ce0.9Gd0.1O2−δ, over 100 redox cycles with the redox pair Fe – Fe2O3 at 900 °C. The low redox stability of the Fe2O3/La0.8Sr0.2FeO3−δ composite oxygen carrier is closely related to that of La0.8Sr0.2FeO3−δ and the extreme redox environment. The increased electronic conductivity of Ce0.9Gd0.1O2−δ under reducing conditions enhances the reaction rate. However, the low electronic conductivity of Ce0.9Gd0.1O2−δ under oxidizing conditions (5 × 10−4 S/cm at 750 °C) progressively promotes the formation of iron oxide product layer, resulting in low syngas selectivity (H2/CO > 2). This work helps design and select a compatible and commercially viable MIEC-supported iron oxide.