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To further improve the basic theory of blast furnace hydrogen-rich smelting and provide a reference for blast furnace hydrogen-rich production, the influences of different conditions on the contact angle and carburization amount of the iron‒coke interface were measured using iron‒coke interface reaction experiments, and the erosion of the three-dimensional morphology of the coke surface by the iron‒coke interface reaction process was analysed. As the degree of coke dissolution increased, the iron‒coke interface contact angle increased, and the amount of carburization decreased. The change in the interface contact angle and carburization amount between iron and coke after reacting with H 2 O was greater than that after reacting with CO 2 , and the interface reaction rate constant and carburization amount were lower for H 2 O than CO 2. When the reaction time increased by 1 min, the differences in the contact angle and carburization amount between the two atmospheres increased by 0.12° and 0.013%, respectively. This improved the permeability of the metal iron for its penetration in the coke layer and was beneficial for stable production. An increase in the reaction temperature and a decrease in the initial carbon mass fraction (w (C)) of metallic iron both increased the carburization rate at the iron‒coke interface, reduced the equilibrium contact angle, improved wettability, and caused severe erosion of the carbon matrix structure on the coke surface. When the temperature exceeded 1673 K, the metal iron could undergo a violent carburization process with coke surface 3, resulting in a wetting phenomenon. The initial w (C) of metallic iron increased by 1%, and the equilibrium contact angle of the iron‒coke interface increased by approximately 3.32°. [Display omitted] • Analyse the interface behavior between iron and coke after reacting with H 2 O and CO 2. • The surface of coke after reacting with H 2 O has poorer wettability with iron. • The effect of various factors on iron-coke wettability was quantitatively analysed. [ABSTRACT FROM AUTHOR]

The minerals in coal are transformed to the coal slag during the entrained-flow coal gasification process. The stable operation of the gasifier relies on the smooth slag tapping process. The flow behavior of coal slag is quantified by the viscosity. The high-iron coal (w(Fe2O3)>15%, ash basis) is widely distributed in China. The iron (Fe2+ or Fe3+) in the coal slag is easily transformed to the metallic iron due to the high content of the reducing gas in the Shell coal gasifier. The presence of metallic iron may lead to the slag blockage or even the unscheduled shut-down of coal gasifier. Hence, it is necessary to investigate the metallic iron precipitation behavior and its effect on coal slag viscosity. The precipitation behavior of metallic iron is investigated by the thermodynamic modelling. Then, the kinetic models of the metallic iron precipitation and agglomeration are built, respectively. Finally, the effects of metallic iron on the crystallization and viscosity of coal slag are quantified. The metallic iron is precipitated under the Shell coal gasifier atmosphere. The high-CaO coal slag favors the metallic iron formation. The metallic iron precipitation model is built based on the diffusion behavior of the reducing gas in the coal slag. In contrast, the metallic iron agglomeration model is established according to the sedimentation of metallic iron particles in the liquid coal slag. Both increasing the CaO content of coal slag and employing high slagging temperature results in the drop of slag viscosity, and the low slag viscosity improves the iron reduction process and metallic iron sedimentation. Therefore, the precipitation and agglomeration of metallic iron are improved. The critical time (tc) of metallic iron agglomeration is proposed and is used as the guide to prevent the metallic iron agglomeration. The metallic iron agglomeration can be alleviated by decreasing the slag tapping temperature or reducing the CaO content of coal slag. The traditional KJMA model is modified by considering the thermodynamic equilibrium content of solid phase in the slag. The metallic iron induces the strong crystallization of anorthite in slag and the slag viscosity is therefore significantly increased. The time of slag viscosity increasing to 25 Pa·s is decreased with the slag tapping temperature, while the time of the solid content achieving the thermodynamic equilibrium is increased. The study demonstrates that the metallic iron precipitation and agglomeration can be alleviated by adopting a low slag tapping temperature, or by using the silicon-rich additive, or co-gasifying with the high-silicon coal during the entrained-flow gasification of high-iron coal.

Iron metal (Fe0) materials enhance the performance of anaerobic digestion (AD) reactors to remove pollutants. Most research focused on the materials' mechanisms and effectiveness in enhancing AD. However, there is scant information on the biogas and sludge quality and quantity and the kinetics of generated methane (CH4) of biogas from the Fe0-aided AD of domestic wastewater (DW). The information is essential for AD reactors' management. This study characterizes the sludge and biogas from Fe0-aided AD of DW and predicts the CH4 yield using the Gompertz, Logistic, and Richard models to study the impact of Fe0 materials on the composition and generation of sludge and biogas. Bench-scale reactors containing DW were fed with Fe0 and operated for 53 days in a quiescent condition, at 24 ± 3 OC room temperature, at 7.3 initial pH value. Steel wool and iron scrap were used as Fe0 sources. A parallel experiment without Fe0 was performed as an operational reference. Results indicate that Fe0 significantly enriched most of the nutrients in sludges, produced well-settling sludge (sludge volume index ≤30), and enriched the CH4 of biogas by more than 12%. Furthermore, all the tested models exhibited good fitting (error

Highlights BC-G@Fe0 nanocomposite was produced through two carbothermal reduction routes. The biomass impregnating-carbonizing route produced graphene-encapsulated iron carbide (Fe3C) nanoparticles. The pyrolyzing-biochar-impregnating-carbonizing route produced graphene-encapsulated nanoscale zero-valent iron particles. BC-G@Fe0 nanocomposites exhibited good heavy metal ion removal performance.

The optimization of the ironmaking process for the preparation of high-purity metallic iron has become an important part of the production of the iron and steel industry due to the increasing demand for steel in the modern industry. This article adopted the soluble anode molten salt electrolysis process to prepare a soluble anode with excellent conductivity by mixing Fe2O3 and C in a molar ratio of 1:3, sintering at 1073 K for 6 h. The metal iron was electrolytically deposited on the cathode by applying a constant current of 0.1 A for 6 h in the NaCl-CaCl2 molten salt system. The anode dissolution and cathode deposition mechanisms were analyzed based on the electrolysis U-t curve. The experimental results showed that the presence of C after sintering reduces the impedance value by reducing Fe2O3 to Fe3O4. During the electrolysis process, Fe2+ in Fe3O4 oxidized to Fe3+ and entered the molten salt, migrated to the vicinity of the cathode, and underwent the reduction process of Fe3+-Fe2+-Fe during the cathodic reduction process. The deposited Fe on the cathode exhibited a dendritic crystal structure with a purity of 99.51%.

The reduction process of lunar regolith simulant was designed to obtain metallic iron (Fe) and utilize lunar resources, focusing mainly on the effect of titanium dioxide (TiO2) on the recovery of metallic Fe from molten slag. Thermodynamic calculations were conducted to predict the equilibrium phases existing at high temperature upon heating the regolith simulant to 1600°C under an oxygen partial pressure of 10-15 atm, in which the metallic Fe coexisted with the molten slag. Based on these predictions, two steps were applied in the experimental procedure: a reduction step followed by a melting step. The results showed that metallic Fe droplets were obtained by aggregating fine metallic Fe particles in the melting step. The viscosity of molten slag was found to decrease when TiO2 was added to the regolith simulant, but the recovery ratio® defined as the weight ratio of the metallic Fe obtained from the aggregation of fine metallic Fe particles to the total amount of Fe in the regolith simulant®also decreased. The wettability between liquid Fe and molten slag improved upon increasing the TiO2 content in the latter. These results indicate that wettability exerts a substantially more dominant effect than the viscosity of molten slag does in the recovery of metallic Fe from regolith simulant. [ABSTRACT FROM AUTHOR]

Iron species can act as electron donors, electron acceptors or serve as a sorbent to co-precipitate contaminants. These properties, along with its relatively low cost as a material, make iron an ideal compound for environmental applications in the removal of pollutants from water and wastewater. This study assesses the use of metallic iron as a reductant for the removal of toxic Cr(VI) from aqueous solutions, as well as the use of hexavalent iron (ferrates) for the removal of organic compounds, turbidity and biological contaminants from water and wastewater. Laboratory-scale experiments show that the Cr(VI) removal efficiency of metallic iron filling materials, such as scrap iron fillings, via reduction to Cr(III) and the subsequent precipitation/filtration of aggregates can reach values over 99.0%. Moreover, the efficiency of ferrates, in situ synthesized via a low-cost Fe0/Fe0 electrochemical cell, in the removal of organic compounds, turbidity and biological contaminants from high-strength industrial wastewater, biologically treated wastewater and natural water can also reach values over 99.0%. The results showed that iron species can be applied in low-cost and environmentally friendly technologies for natural water remediation and wastewater treatment. Furthermore, the study showed that the challenge of an iron material's surface passivation, as well as of ferrates' procurement cost and stability, can be resolved via the application of ultrasounds and via in situ ferrate electrosynthesis. [ABSTRACT FROM AUTHOR]

The aim of the present study was to provide new knowledge regarding the effect of non-expansive inert material addition on anionic pollutant removal efficiency in Fe0-H2O system. Non-disturbed batch experiments and continuous-flow-through column tests were conducted using CrVI as a redox–active contaminant in three different systems: "Fe0 + sand", "Fe0 only" and "sand only". Both experimental procedures have the advantage that formation of (hydr)oxide layers on Fe0 is not altered, which makes them appropriate proxies for real Fe0-based filter technologies. Batch experiments carried out at pH 6.5 showed a slight improvement of CrVI removal in a 20% Fe0 system, compared to 50, 80 and 100% Fe0 systems. Column tests conducted at pH 6.5 supported results of batch experiments, revealing highest CrVI removal efficiencies for "Fe0 + sand" systems with lowest Fe0 ratio. However, the positive effect of sand co-presence decreases with increasing pH from 6.5 to 7.1. Scanning electron microscopy—energy dispersive angle X-ray spectrometry and X-ray diffraction spectroscopy employed for the characterization of Fe0 before and after experiments indicated that the higher the volumetric ratio of sand in "Fe0 + sand" system, the more intense the corrosion processes affecting the Fe0 grains. Results presented herein indicate the capacity of sand at sustaining the efficiency of CrVI removal in Fe0-H2O system. The outcomes of the present study suggest that a volumetric ratio Fe0:sand = 1:3 could assure not only the long-term permeability of Fe0-based filters, but also enhanced removal efficiency of CrVI from contaminated water. [ABSTRACT FROM AUTHOR]

Metallic iron (Fe0) within lunar soil grains can affect their visual and near-infrared spectra, adhesion, biological toxicity, and electrostatic migration characteristics. The Fe0 particle therefore is an important component of lunar soil. This study devised a high-temperature carbothermic reduction method for preparing Fe0 via graphite reduction of Chinese Lunar Regolith Simulant (CLRS-2) in an argon atmosphere, which is similar to the Fe0 in the agglutinitic glass of lunar samples. The X-ray diffraction and electron microscopy data show that the mixture of lunar soil simulants and graphite heated at high temperature rapidly quenched to form a glassy phase with dispersed Fe0 particles, the microstructure of which is consistent with the α-Fe (bcc) in lunar soil. This paper also discusses the main influencing factors for preparing Fe0, such as the ratio of raw materials, heating temperature, and holding time. The optimal experimental conditions are a graphite-to-CLRS-2 mass ratio of 1.0: 27.0 (Fe/C = 2.0: 2.6), reduction temperature of ∼1600 °C, and holding time of ∼4 h, which produce single-phase α-Fe with an average particle size of ∼180 ± 10 nm and no residual impurities (e.g., graphite). [ABSTRACT FROM AUTHOR]

Here in this paper, the effect of temperature on reduction behaviors and microstructural changes of magnetite by hydrogen is studied in a laboratory micro‐fluidized bed reactor. The phase compositions and microstructures of reduced samples are investigated by X‐ray diffraction, scanning electron microscope, and Brunauer–Emmett–Teller method. The results show that a metallization degree of 90.85% is obtained under the optimal conditions of reduction temperature of 570 °C, H2 concentration of 80%, and reduction time of 40 min. The metallization degree gradually increases with the temperature, and the magnetite (Fe3O4) is directly reduced to porous metallic iron (Fe) in the temperature range of 470–570 °C. While, the magnetite is first reduced to wüstite (FeO) and then further reduced to metallic iron with a dense structure in the temperature range of 570–670 °C. The dense metallic iron layer forms on the raw magnetite particle surface, which prevents the contact and reaction of the reducing gas with the iron oxide, resulting in a sharp decrease in the metallization degree. [ABSTRACT FROM AUTHOR]

Separation of iron and titanium by reduction-corrosion method from ilmenite had the advantages of less pollution, simple process, and low cost compared with other methods. To identify the determinants for corrosion reaction of reduced ilmenite, the corrosion electrochemistry of metallic iron in ammonium chloride solution was carried out. The metallic iron was oxidized to form dense Fe2O3 and Fe3O4 in NH4Cl solution at pH of 3.60, resulting in the passivation of metallic iron electrode surface. However, the anode passivation film was destroyed by the chloride ions in the NH4Cl solution, which promoted the corrosion reactions of metallic iron. The corrosion of metallic iron in the 1.60 wt.% NH4Cl solution was controlled by the cathode reaction with a control degree of 95.86%. Decreasing the cathodic polarization could improve the corrosion rate of metallic iron. The decrease of pH value in electrolyte promoted the anode reaction of metallic iron in the NH4Cl solution and reduced the passivation of metallic iron. The Ca2+ and Mg2+ ions in electrolyte increased the difficulty of the metallic iron corrosion reaction. The Fe(OH)3 accumulated in electrolyte slowed down the corrosion reaction rate of metallic iron. [ABSTRACT FROM AUTHOR]

Results from different research suggest that metallic iron (Fe0) materials enhance anaerobic digestion (AD) systems to remove organics (chemical oxygen demand (COD)), phosphorus and nitrogen from polluted water. However, the available results are difficult to compare because they are derived from different experimental conditions. This research characterises the effects of Fe0 type and dosage in AD systems to simultaneously remove COD and nutrients (orthophosphate (PO43−), ammonium (NH4+), and nitrate (NO3− Lab-scale reactors containing domestic sewage (DS) were fed with various Fe0 dosages (0 to 30 g/L). Batch AD experiments were operated at 37 ± 0.5 °C for 76 days; the initial pH value was 7.5. Scrap iron (SI) and steel wool (SW) were used as Fe0 sources. Results show that: (i) SW performed better than SI on COD and PO43− removal (ii) optimum dosage for the organics and nutrients removal was 10 g/L SI (iii) (NO3− + NH4+) was the least removed pollutant (iv) maximum observed COD, PO43− and NO3− + NH4+ removal efficiencies were 88.0%, 98.0% and 40.0% for 10 g/L SI, 88.2%, 99.9%, 25.1% for 10 g/L SW, and 68.9%, 7.3% and 0.7% for the reference system. Fe0-supported AD significantly removed the organics and nutrients from DS. [ABSTRACT FROM AUTHOR]

Iron-based oxides are an important class of magnetic materials and have extremely important uses in the electronics industry. The preparation of iron oxide into nanomaterials with special properties has aroused great interest and widespread concern from researchers. This article aims to study the preparation and characterization of low-dimensional nano-materials of iron oxides. In this paper, iron oxide nanomaterials were prepared by microemulsion method, and compared with other conventional methods such as hydrothermal method, thermal decomposition method and coprecipitation method to prepare the purity of iron oxide nanomaterials, the total yield of the experiment, the stability of the finished products Comparative analysis of the four aspects of sex and the total cost of the experiment to summarize the experimental data. The research results show that the microemulsion method has a purity of up to 99% and a yield of 86% compared to the other three methods. In terms of stability, the finished product prepared by the microemulsion method has better stability within two months. There is no obvious change; however, the finished products prepared by the other three methods have different degrees of degradation after one month, which fully proves that the finished products prepared by the microemulsion method have better stability. Comparing its cost, it is found that there is no significant difference in experimental cost. Therefore, the preparation of iron oxide low-dimensional nanomaterials by microemulsion method provides an important theoretical basis for the preparation of iron oxide nanomaterials in the future. [ABSTRACT FROM AUTHOR]

Abstract Japanese cypress (Chamaecyparis obtusa) wood powder impregnated with Fe3+ ions was carbonized using one-step and two-step procedures, and the iron-loaded charcoal was examined using Mössbauer and Raman spectroscopy to elucidate the physicochemical states of iron and carbon after carbonization at various temperatures. In the one-step procedure, the Mössbauer spectra confirmed that charcoal carbonized at 750 °C and 800 °C contained Fe3C, suggesting that the reduction of Fe3+ started at lower than 750 °C. The content of Fe3C increased substantially in charcoal carbonized at 850 °C and 900 °C, and metallic iron (γ-Fe and/or α-Fe) was also detected in these charcoal samples. Raman spectral line-shapes of the charcoal carbonized at 750 °C and 800 °C were notably different from those of charcoal carbonized at 850 °C and 900 °C, which indicated that crystallization of carbon progressed rapidly in the temperature range 800–850 °C. The changes in Raman spectra probably corresponded to those in the Mössbauer spectra, namely, the graphitization was closely related to the reduction of Fe3+. The degree of graphitization in the charcoal carbonized at 850 °C using the two-step procedure was higher than that using the one-step procedure. Mössbauer spectra suggested that the two-step carbonization enhances the yield of ferromagnetic iron species in iron-loaded charcoal.

Iron oxide (maghemite and magnetite) nanoparticles are the most commonly used magnetic materials in nanomedicine because of their high biocompatibility. However, their low saturation magnetization (60–90 emu/g) limits their applicability. Here, we report a new core–shell (Fe@FexOy) nanoring system, which combines the high magnetic saturation of a metallic iron core (220 emu/g) and the biocompatibility of an iron oxide shell. To produce these nanostructures, hematite (α-Fe2O3) nanorings were annealed in a H2 gas atmosphere for different periods to optimize the amount of metallic iron percentage (δ) in the system. Thus, nanostructures with different magnetic saturation (97 to 178 emu/g) could be obtained; based on their metallic iron content, these particles are labeled as Vortex Iron oxide Particle δ (VIPδ). Micromagnetic simulations confirmed that the VIPδ nanorings exhibit a vortex configuration, guaranteeing low remanence and coercitivity. Moreover, the system shows good biocompatibility in various assays as determined through cell viability measurements performed using two different human cell lines, which were exposed to VIP78% for 24 h. Therefore, VIPδ nanorings combine a magnetic vortex state and biocompatibility with their high magnetic saturation and can thus serve as a platform that can be tuned during the synthesis based on desired biomedical application.

Iron species can act as electron donors, electron acceptors or serve as a sorbent to co-precipitate contaminants. These properties, along with its relatively low cost as a material, make iron an ideal compound for environmental applications in the removal of pollutants from water and wastewater. This study assesses the use of metallic iron as a reductant for the removal of toxic Cr(VI) from aqueous solutions, as well as the use of hexavalent iron (ferrates) for the removal of organic compounds, turbidity and biological contaminants from water and wastewater. Laboratory-scale experiments show that the Cr(VI) removal efficiency of metallic iron filling materials, such as scrap iron fillings, via reduction to Cr(III) and the subsequent precipitation/filtration of aggregates can reach values over 99.0%. Moreover, the efficiency of ferrates, in situ synthesized via a low-cost Fe0/Fe0 electrochemical cell, in the removal of organic compounds, turbidity and biological contaminants from high-strength industrial wastewater, biologically treated wastewater and natural water can also reach values over 99.0%. The results showed that iron species can be applied in low-cost and environmentally friendly technologies for natural water remediation and wastewater treatment. Furthermore, the study showed that the challenge of an iron material’s surface passivation, as well as of ferrates’ procurement cost and stability, can be resolved via the application of ultrasounds and via in situ ferrate electrosynthesis.

Results are presented from the first study of the effect such organic inhibitors of radical reactions as p-cumylphenol, 2,6-di-tert-butyl-4-methylphenol (ionol), 2,2,6,6-tetramethylpiperidine, 2,2,6,6-tetramethylpiperidine-1-oxyl, and elemental sulfur have on the formation of ferrous didodecanethiolate [Fe(SDd)2] in the reaction between dodecanethiol (DdSH) and metallic iron with mechanochemical activation in polar and nonpolar solvents, such as hexane, dibutyl disulfide, 3-heptene, styrene, and ethanol. A previously unknown tribochemical reaction of DdSH and pyrite is revealed. [ABSTRACT FROM AUTHOR]

In order to determine the synergistic effects of the mixed additives of Fe and other catalysts on the yields and characteristics of bio-oil products, hydrothermal liquefaction (HTL) of pinewood sawdust (PW) was performed at 300 °C for 30 min (biomass/water mass ratio = 1:10) in the presence of metallic iron (Fe), other homogeneous/heterogeneous catalysts (Na 2 CO 3 , NaOH, FeSO 4 , MgO, Ru/C, FeS), as well as mixed additives. The results indicated that the metallic Fe could increase the yield and promote the degree of hydrodeoxygenation of bio-oil products. Noticeable synergistic effects on improving the bio-oil yields were found in the presence of mixed additives of Fe and an alkali catalyst (Na 2 CO 3 /NaOH) or FeS. The maximum bio-oil yield and the most energy recovery from bio-oil (81%) were obtained with Fe + Na 2 CO 3. In addition, the combination of Fe + Ru/C produced bio-oil with the highest carbon and hydrogen contents, the highest HHV (30.93 MJ/kg), as well as the lowest contents of oxygenated compounds and the largest amount of hydrocarbons. In summary, this work demonstrates the synergistic effects of the mixed additives of Fe and several catalysts (Na 2 CO 3 , FeS and Ru/C) in HTL of woody biomass, promoting both yields and quality of bio-oil products. • Mixed additives of Fe and other catalysts were applied during HTL of woody biomass. • Synergistic effects between Fe and catalysts on bio-oil yields/properties were found. • Maximum bio-oil yield and energy recovery was obtained with Fe + Na2CO3. • Hydrodeoxygenation of bio-oil was promoted by Fe + Ru/C or Fe + FeS. • Both yields and quality of bio-oil could be improved with Fe and suitable catalysts. [ABSTRACT FROM AUTHOR]

One of the key problems associated with current trends in the development of the iron and steel industries in Russia and CIS countries concerns the recycling of industrial waste products. This problem arose as a result of extensive industry development combined with changing consumer attitudes to the environment involving tens of millions of tons of metallurgical production wastes occupying vast territories and destroying land utility by polluting the soil and water basin. The present paper analyses the current state of steelmaking slag recycling both in CIS and non-CIS countries. The accumulated experience of world practice in solving the problem of steelmaking slag recycling is described in detail. Particular attention is paid to converter slag recycling in the metallurgical processes of JSC ArcelorMittal Temirtau, in which converter scrap is utilized as part of the sinter charge. A generalized analysis of the data on the yield of slag processing products and the iron content of scrap and dump slag indicated the total amount of extracted iron (27.6%) to be significantly less than its proportion in the dump (64.6% of the total iron content). The possibility of increasing the yield of the magnetic part from the converter slag fraction and metallic iron extraction was experimentally confirmed. Calculated sintering indicators for sinter scrap are given: a 0.2% increase in the iron content is accompanied by an increase in the consumption of fine coke by 0.2 kg per 1 ton of the finished sinter. [ABSTRACT FROM AUTHOR]

Vanadium‑titanium magnetite, a kind of composite ore with iron, vanadium and titanium, has not been utilized on large scale by steel plants. An efficient and clean utilization technique for vanadium‑titanium magnetite based on fluidized bed hydrogen reduction was developed in present study. The effect of reduction temperature, H 2 concentration, reduction time and gas flow rate on the metallization degree of the reduced product were studied. The phase compositions and microstructures of sample were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Experimental results indicated that a metallization degree of 91.30% was obtained under the optimal conditions of reduction temperature of 850 °C, H 2 concentration of 80%, reduction time of 30 min and gas flow rate of 900 mL·min−1. As the number of metallic iron grains increased, adjacent metallic iron grains gradually aggregated and formed flakes. While, the metallic iron grains precipitated by reduction of raw ilmenite gathered into strips. It is noteworthy that no intermediate phase wustite is detected in all reduced samples, which may be due to the wustite is immediately reduced or decomposed after being formed. Therefore, the possible reduction paths of titanomagnetite are suggested as follows: (1) Fe 3- x Ti x O 4 → Fe + FeTiO 3 → Fe + TiO 2 , (2) Fe 3- x Ti x O 4 → FeO + FeTiO 3 → Fe + TiO 2 , 0.5 < x < 1. [Display omitted] • Efficient fluidized reduction technique was proposed for vanadium-titanium magnetite. • No intermediate phase FeO was detected in all reduced products. • Two possible reduction paths for the reduction of titanomagnetite were suggested. • Metallization degree of 91.30% was obtained in final reduced products. [ABSTRACT FROM AUTHOR]

Effects of different coals and coke on the direct reduction of vanadium titanomagnetite concentrate (VTC) added with calcium carbonate were investigated. Lignite was found to provide a better reduction effect than bituminous coal, coke or anthracite, mainly because the gasification reactivity of lignite was obviously better than that of other three reductants, and the metallization degree could reach 95.11 wt% when used lignite. Coals and coke showed little influence on the existence form of Ti in the reduction product, where Ti existed mainly as calcium titanate. Additionally, lignite, coke or anthracite all promoted the growth of metallic iron and calcium titanate particles batter than bituminous coal, which were conducive to subsequent magnetic separation. However, the use of coke or anthracite gave lower purity calcium titanate because of the existence of unreduced iron. Furthermore, these reductants caused large amounts of FeS around metallic iron particles, which hindered the further reduction of iron. [ABSTRACT FROM AUTHOR]

An experimental study of the form of metallic iron deposited from silicate melt at a drastic fO2 decrease was conducted at 1400°C and 1 atm total pressure. The oxygen fugacity was controlled by CO/CO2 gas mixture. It was demonstrated that the metallic iron initially forms a network of euhedral crystals near the melt surface. With an increase in experimental duration, the iron loses its crystalline morphology. At a high magnification, it looks like being melted before quenching, although the experimental temperature was fixed at ca. 140°C below the melting point of pure iron. Experimental studies with similar results are reviewed. [ABSTRACT FROM AUTHOR]

Effects of direct reduction time of vanadium titanomagnetite concentrate (VTCE) on the preparation and photocatalytic performance of calcium titanate were investigated in this study. It was found that extending the reduction time could not only promote the formation of calcium titanate, but also facilitate the reduction of iron minerals in the reduction products. The optimum reduction time was 180min under the conditions of CaCO3 dosage of 18wt%, reduction temperature of 1400? and lignite dosage of 70wt%. The reduced iron (Fe grade of 90.95wt%, Fe recovery of 92.21wt%) and calcium titanate were obtained via grinding-magnetic separation. Moreover, calcium titanate prepared via the direct reduction method could be used as a photocatalyst, where the degradation degree of methylene blue increased from 25.13% to 60.14% with the addition of calcium titanate. Furthermore, Langmuir Hinshelwood fitting results indicated that the degradation of methylene blue by the calcium titanate prepared under different reduction times conformed to first-order reaction kinetics, where the photocatalytic degradation rate of methylene blue was noted to be the highest for a reduction time of 180 min. [ABSTRACT FROM AUTHOR]

To establish a novel approach for VOCs resource utilization, coupled o-xylene oxidation and hematite reduction was investigated in this study in a high-temperature gas-solid reactor in the temperature range 300–700 °C. As the o-xylene-containing inert gas (N2) stream traveled through the hematite particle bed, its reaction behavior was determined in programmed heating and constant temperature modes. Consequently, the effect of bed temperature, flow rate and o-xylene inlet concentration on both o-xylene removal performance and degree of hematite reduction was studied. The raw hematite and solid products were analyzed by TGA, XRF, XRD and SEM-EDS. The results showed that a temperature above 300 °C was required to completely eliminate o-xylene by hematite, and both o-xylene removal capacity and degree of hematite reduction at 5% breakthrough points enhanced on increasing the temperature and decreasing the flow rate. The increment in temperature from 300 °C to 700 °C led to a gradual reduction of Fe2O3 to Fe3O4, FeO and metallic iron. Thus, this study provides a novel, economic and promising technology for treating the VOC pollutants.

Japanese cypress (Chamaecyparis obtusa) wood powder impregnated with Fe3+ ions was carbonized using one-step and two-step procedures, and the iron-loaded charcoal was examined using Mössbauer and Raman spectroscopy to elucidate the physicochemical states of iron and carbon after carbonization at various temperatures. In the one-step procedure, the Mössbauer spectra confirmed that charcoal carbonized at 750 °C and 800 °C contained Fe3C, suggesting that the reduction of Fe3+ started at lower than 750 °C. The content of Fe3C increased substantially in charcoal carbonized at 850 °C and 900 °C, and metallic iron (γ-Fe and/or α-Fe) was also detected in these charcoal samples. Raman spectral line-shapes of the charcoal carbonized at 750 °C and 800 °C were notably different from those of charcoal carbonized at 850 °C and 900 °C, which indicated that crystallization of carbon progressed rapidly in the temperature range 800–850 °C. The changes in Raman spectra probably corresponded to those in the Mössbauer spectra, namely, the graphitization was closely related to the reduction of Fe3+. The degree of graphitization in the charcoal carbonized at 850 °C using the two-step procedure was higher than that using the one-step procedure. Mössbauer spectra suggested that the two-step carbonization enhances the yield of ferromagnetic iron species in iron-loaded charcoal. [ABSTRACT FROM AUTHOR]

Thermomagnetic analysis of samples from two sections of lava layers of the Late Cenozoic basalt lava river in the Malyi Yenisei valley is carried out. The main magnetization carrier in the studied basalts is titanomagnetite with the Curie points of 100–120°C which is frequently substantially oxidized both single-phase and heterophase up to magnetite. It is likely that some part of metallic iron in the studied samples has also been oxidized and even disintegrated, which resulted in the significant scatter of iron concentration across the flow against which, however, the increasing trend of iron concentration in the lava flow from the top downwards is observed. The relative magnitude of this increase (iron concentration gradient along the vertical of the lava flow) is almost constant for all flows of the lava sequence probably indicating the decisive role of gravity in iron particle precipitation in the lava. Based on the synthesis of iron particle data from different objects and different regions of the world, this correlation with gravity also follows from the very similar shapes of particle size histograms of iron. This is most clearly seen from the same particle size modes (10–20 μm). Another important finding is that this constant mode of iron particle size does not depend on age and origin of rock as well as on the type of particle source (terrestrial or extraterrestrial). [ABSTRACT FROM AUTHOR]

• Aqueous washing process for oil removal from iron grinding swarf was investigated. • Two different commercial reagents, Micro-90 and Detergent 8 was used. • Detergent 8, 100% oil was removed after three washing cycles. • The preliminary reuse test of the Detergent 8 solution was also conducted. This research focused on the recovery of valuable materials from ferrous grinding swarf. We received the sample from the automobile industry. The sample has consisted of approximately 20 wt% moisture and 80 wt% residue (oil and soild). The chemical composition of the oven-dried sample was approximately 87 wt% iron. In this study, aqueous washing process for oil removal from ferrous grinding swarf was investigated with two different commercial reagents, Micro-90 and Detergent 8. Three different amounts of solids (2, 3, and 4 g) were mixed with 20 mL of diluted reagents for the aqueous washing. In the Micro-90 solution, about 80% of the oil was removed after three washing cycles at a solids content less than 3 g/20 mL. On the other hand, when using Detergent 8, 100% oil was removed after three washing cycles at a solids content of less than 3 g/20 mL. Pulp density was an important factor in determining oil removal efficiency. For the scale-up experiment, different washing methods such as ultrasonication and overhead stirrer were examined. The preliminary reuse test of the Detergent 8 solution was also conducted for the feasibility of the aqueous washing process. [ABSTRACT FROM AUTHOR]

Nitrate reduction was optimized in water from the Siilinjärvi/Finland mine site with iron powder and iron nanoparticles. Iron waste from a mold machining industry was then tested as a potential alternative. Complete reduction of nitrate from the mine water was achieved with the iron powder and nanoparticles at pH 2. The iron waste, though less efficient, still achieved 53% nitrate reduction. Examination of the surface of the iron powder and waste by SEM–EDS showed iron corrosion: crystals of iron oxides grew on the iron surface as the pH increased during NO3− reduction, until about pH 5. The major by-product of the NO3− reduction of mine water was NH4+, with low NO2− concentrations (< 7%). Although iron powder and nanoparticles were more reactive, the iron waste results are promising. Despite its low BET surface area, the use of iron waste to treat high volumes of mine water would appear to have economical and sustainable advantages. More efficient NO3− reduction could possibly be attained with iron waste of higher BET surface area and/or by combining it with other chemical treatments. [ABSTRACT FROM AUTHOR]

The formation of calcium titanate in the carbothermic reduction of vanadium titanomagnetite concentrate (VTC) by adding CaCO3 was investigated. Thermodynamic analysis was employed to show the feasibility of calcium titanate formation by the reaction of ilmenite and CaCO3 in a reductive atmosphere, where ilmenite is more easily reduced by CO or carbon in the presence of CaCO3. The effects of CaCO3 dosage and reduction temperature on the phase transformation and metallization degree were also investigated in an actual roasting test. Appropriate increase of CaCO3 dosages and reduction temperatures were found to be conducive to the formation of calcium titanate, and the optimum conditions were a CaCO3 dosage of 18wt% and a reduction temperature of 1400°C. Additionally, scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) analysis shows that calcium titanate produced via the carbothermic reduction of VTC by CaCO3 addition was of higher purity with particle size approximately 50 µm. Hence, the separation of calcium titanate and metallic iron will be the focus in the future study. [ABSTRACT FROM AUTHOR]

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Effects of calcium compounds on the carbothermic reduction of vanadium titanomagnetite concentrate (VTC) were investigated. It was found that calcium compounds had great effects on the metallization rate of the reduction product, the order of the metallization rate of reduction product being CaCO3 > no additive > CaSO4 > CaCl2, which indicated that the addition of CaCO3 was more conducive to promoting the reduction of iron than other calcium compounds. Gas analysis showed that there were mainly two processes in the carbothermic reduction of VTC, a solid-solid and a solid-gas reaction. The concentrations of CO and CO2 were highest when CaCO3 was added, while that in a roasting system decreased the most when CaCl2 was added. X-ray diffraction (XRD) analysis showed that calcium compounds could change the reduction process of ilmenite in VTC. The phase compositions of the reduction products were changed from metallic iron (Fe) and anosovite (FeTi2O5) to metallic iron (Fe) and perovekite (CaTiO3) when calcium compounds were added. Additionally, CaSO4 and CaCl2 could significantly promote the growth of metallic iron particles, though the existence of Fe-bearing Mg2TiO4 in reduction products was not conducive to the reduction of iron. The formation of FeS would further hinder the reduction of iron after adding CaSO4. [ABSTRACT FROM AUTHOR]

The Ramgarh structure (rim-to-rim diameter ~2.4 km) in the Vindhyan Supergroup of sedimentary rocks (including sandstone, shale and minor limestone) of the Mesoproterozoic age in the west-central India, is India’s third confirmed asteroid impact crater. This eroded structure is roughly rectangular in shape and resembles to the Barringer Crater, USA. The presence of central peak and its current crater diameter/depth ratio of ~12 well corroborate the range (10–20) of terrestrial complex asteroid impact craters. The mm-sized, iron-rich (FeO ~50 wt.% in average), spherule-like particles, recovered from the alluvium inside the Ramgarh structure, have internal morphology similar to those of the accretionary lapilli described in known impact craters. The in-situ LA-ICP-MS analyses also suggested high Co–Ni (up to 13,000 and 2500 ppm, respectively)-rich areas locally within these spherules/lapilli. A few non-in-situ, mm-sized particles, recovered from the rim of the structure show the presence of coesite, one of the diagnostic indicators of shock metamorphism. A few fragments of iron-rich, Ca–Al–silicate glasses recovered from the soil inside the structure and outside of the western crater rim include the presence of dendritic magnetite with occasional inclusions of relict native iron. Our microprobe analyses confirm that these metallic irons contain high proportions of Co (~350–3000 ppm), Ni (~200–4000 ppm) and Cu (~2200–7000 ppm) and possibly could be the relict component of a Cu-rich iron meteorite impactor. The field observation and relative enrichment of compatible and incompatible trace elements in the spherule-like substance (recovered from the alluvium inside the Ramgarh structure) as compared to target rocks suggests that hydrothermal activity played an important role in the evolution of the crater. [ABSTRACT FROM AUTHOR]

Red mud is a solid waste produced during alumina extraction from bauxite. In this study, we pretreated red mud by segregation roasting to convert the iron from weak magnetic minerals to ferromagnetic minerals and then subjected the material to grinding and low intensity magnetic separation to obtain iron concentration. The effects of the chlorinating agent type, chlorinating agent dosage, reducing agent dosage, temperature, reaction time, additive, grinding fineness and magnetic field strength on the iron concentrate grade and recovery rate are studied. At a red mud/KCl/coke/ Na2SO4 mass ratio of 100:15:15:10, segregation roasting at 1100°C for 60 min, the roasted ore is ground to about 95 wt.% passing 0.045 mm and a magnetic field strength of 0.22 T, the final iron concentrate grade is 78.29% and the recovery is 84.08%, which is an efficient improvement of the valuable metal iron in red mud. The X-Ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy analysis of the iron concentrate shows that before the segregation roasting, the precious metal iron in the red mud is mainly in the form of Fe2O3. After the segregation roasting, the iron is transformed into a new iron mineral phase mainly composed of metal Fe and Fe3O4. The main impurities in the iron concentrate are calcium, silicon and aluminum. [ABSTRACT FROM AUTHOR]

The dynamics of interaction between metallic iron and aqueous solutions of three preparations of humic coal substances from different manufacturers is analyzed. Humic substances are characterized via elemental analysis, NMR spectroscopy, size-exclusion chromatography, electronic absorption spectroscopy, and chemical analysis. Distinctions are observed between the investigated humic substances in the content of aromatic moieties, the degree of their substitution, the content of carboxylic groups, and the degree of oxidation. It is shown that regardless of the background of humic substances, the interaction between their solutions and iron is based on the same set of consecutive reactions, which can be divided into three basic stages of interaction using data on the changes in easily controllable parameters (redox potential, pH, and solution absorbance). These stages of interaction are qualitatively described in Pourbaix diagram coordinates. Features of the structural and group composition of humic substances result in different times of the corresponding stages of interaction. Based on an analysis of the main components, a way of describing the complicated sequence of reactions between humic substances and iron in the coordinates of a two-factor plane is proposed to allow the clear attribution of experimentally measured parameters of the reaction medium to a certain stage of interaction between metallic iron and aqueous solutions of humic substances, regardless of the specific properties of the latter. [ABSTRACT FROM AUTHOR]

Highlights • The addition of Fe in HTL leads to maximum bio-oil yield of 37% wt. at 320 °C. • During the process Fe is transformed in Fe 3 O 4 producing H 2 in situ. • Presence of H 2 leads to enhanced oil quality, HHV of 32 MJ/kg is reached at 320 °C. • Carbon recovery in bio-crude when Fe is used reaches the very high value of 53%. Abstract Hydrothermal liquefaction (HTL) is a promising technology for the production of high quality bio- crude. Aim of this study is to investigate the effect of the addition of iron powder into the HTL process of oak wood biomass. Fe in HTL conditions should be oxidized by water into Fe 3 O 4 producing H 2 in situ which is responsible for the increase of bio-crude yield. Furthermore, the presence of Fe contributes to enhance bio-crude quality due to the presence of Fe 3 O 4 which is recognized to have catalytic activity in hydrogenation reactions. Tests in presence of oxides containing Fe in higher oxidation number such as Fe 3 O 4 and Fe 2 O 3 were performed. The tests were conducted with water to biomass ratio of 5, in a range of temperature of 260–320 °C, the reaction time was set to 15 min and the catalysts were added in an amount of 10% with respect to the biomass weight. Highest bio-crude yields of about 40% were reached using zerovalent Fe. Tests performed in presence of Fe 3 O 4 gave intermediate behaviour while no improvements were registered adding Fe 2 O 3. These results confirmed the positive dual effect of Fe addition. In fact, the H/C ratio in the bio-oil increases of about 15% with respect to the reaction conducted without iron-based compounds and Gas Chromatography–Mass Spectrometry analyses showed that the presence of aliphatic compounds is improved. [ABSTRACT FROM AUTHOR]

Highlights • The effect of atmosphere on the viscosity of fully molten slag is weak. • The effect of metallic iron on slag viscosity is revealed for the first time. • The metallic iron acts as crystal seed and promotes the anorthite crystallization. • The crystallization of gehlenite is not influenced by metallic iron precipitation. Abstract Viscosity behavior of coal ash slag in the slagging gasifier is the key for the stable operation. The oxidation state of iron in the slag is sensitive to the gas chemistry, which influences the viscosity behavior. The atmosphere in the gasifier varies from weak oxidizing to strong reducing, and the effect on slag viscosity behavior is still not available. In this study, viscosities of two coal ash slags of which chemical compositions located in the anorthite and gehlenite regions in the phase diagram SiO 2 -Al 2 O 3 -CaO, were investigated under argon, mild reducing atmosphere and strong reducing atmosphere by the high temperature rotating viscometer. The wet chemical analysis was used to analyze the oxidation state of iron in coal ash slag. Thermodynamic calculation, XRD analysis and SEM-EDX were used to investigate crystallization behavior of the slags during cooling. The results show that the effect of atmosphere on the viscosity of fully molten slag is not obvious. The slag has the lowest viscosity value under the mild reducing atmosphere for the abundance of Fe2+ (80% total iron). Under strong reducing atmosphere, the precipitation of metallic iron in coal ash slag increases slag viscosity as the content of network modifier declines. However, the effect of atmosphere on the slag viscosity is significant after the slag crystallizes. For the slag located in the anorthite region, the presence of metallic iron acts as crystal seed and significantly accelerates the crystallization of anorthite, resulting in a sharp increase of slag viscosity. However, the effect of atmosphere on the viscosity of slag located in the gehlenite region is not obvious because the crystallization propensity of gehlenite is too strong to be influenced by metallic iron precipitation. [ABSTRACT FROM AUTHOR]

Abstract An integrated steel plant generates 200–250 kg of steel making slag for every tonne of steel produced. These slags contain non-uniformly distributed iron in metallic form, inevitably carried into the slag pot during de-slagging. The steel slag is subjected to crushing/magnetic separation to generate different sizes of slag products with varying metallic values. Based on size and metallic content, these products are recycled in sinter base mix, iron making units and as scrap in steel making process. Hence accurate analysis of Fe-metallic in these samples is imperative for better process control. Due to non-uniform mixing and solidification of steel & slag in de-slagging and dumping practice, precise quantification of the metallic portion in these samples is extremely difficult. Existing methods followed by slag processing agencies has always been doubtful. Moreover, uniformity of constituents in a small sample size cannot be ensured even by best of the sampling techniques. In the present work, all the slag products have been subjected to different measurement techniques to develop a method to determine the metallic iron content accurately in the steel-making slags. Separate methods have been formulated for low metallic and high metallic content slag samples based on the dominant characteristics. Specific density balance and grinding-sieving methods are proposed for more practical and accurate measurement. Best sampling technique and optimum sample size have also been suggested for each method. In addition to increase in the efficiency of the process, where it is recycled, accurate analysis of Fe-metallic in slag helps in improving the magnetic separation technique and the process of its application. [ABSTRACT FROM AUTHOR]

In India, ilmenite is considered as a major mineral reserve for the extraction of titanium. During the processing of ilmenite to produce titanium dioxide, huge amount of iron oxide is generated and dumped as waste. According to an approximation, 0.7 ton of iron oxide waste is generated for one ton of synthetic rutile production. This waste iron oxide has great potential to be utilized as resource of iron. Therefore, the present work deals with the carbothermic reduction studies of iron oxide waste generated during the ilmenite processing. The spent graphite electrode of electric arc furnace was used as reductant for the reduction studies. Different parameters such as reduction temperature, residence time and weight ratio of iron oxide/reductant were investigated. Reduction studies were carried out by varying the residence time at 15, 30, 60 and 120 min. With an increase in reduction temperature and residence time, percent reduction was found to be increased. Maximum reduction value of 95% was obtained at optimized reduction condition. After reduction, fine powder of metallic iron was obtained, which was characterized by XRD and particle size analyzer. The generated fine powder of metallic iron had direct application and high market value. [ABSTRACT FROM AUTHOR]

Advanced oxidation processes (AOPs) based on peracetic acid (PAA) has been extensively concerned for the degradation of organic pollutants. In this study, metallic iron-modified sludge biochar (Fe-SBC) was employed to activate PAA for the removal of sulfamethoxazole (SMX). The characterization results indicated that FeO and Fe 2 O 3 were successfully loaded on the surface of the sludge biochar (SBC). Fe-SBC/PAA system achieved 92% SMX removal after 30 min. The pseudo-first-order kinetic reaction constant of the Fe-SBC/PAA system was 7.34 × 10−2 min−1, which was 2.4 times higher than the SBC/PAA system. The degradation of SMX was enhanced with increasing the Fe-SBC dosage and PAA concentration. Apart from Cl−, NO 3 − and SO 4 2− had a negligible influence on the degradation of SMX. Quenching experiments and electron paramagnetic resonance (EPR) techniques identified the existence of reactive species, of which CH 3 C(O)OO•, 1O 2 , and O 2 •- were dominant reactive species in Fe-SBC/PAA system. The effect of different water matrices on the removal of SMX was investigated. The removal of SMX in tap water and lake water were 79% and 69%, respectively. Four possible pathways for the decay of SMX were presented according to the identification of oxidation products. In addition, following the ecological structure-activity relationship model (ECOSAR) procedure and the germination experiments with lettuce seeds to predict the toxicity of the intermediates. The acute and chronic ecotoxicity of SMX solution was dramatically diminished by processing with Fe-SBC/PAA system. In general, this study offered a prospective strategy for the degradation of organic pollutants. [Display omitted] • PAA was efficiently activated by Fe-SBC to degrade SMX. • The Fe-SBC/PAA system achieved maximum 92% SMX degradation within 30 min. • CH 3 C(O)OO•, 1O 2 , and O 2 •- were considered to be dominant active species for SMX degradation. • Fe-SBC exhibited relatively high reusability without notable metal leaching. [ABSTRACT FROM AUTHOR]