Formation Of γ-Fe2O3 Research Articles

Decarbonization of siderite in the water-rich upper mantle

The aqueous fluids within subducted slabs have the potential to influence the form of carbonate presence and the carbon cycling process. Experiments were performed on resistive heating diamond anvil cell using siderite crystals and grains with water under conditions of pressure as high as 11.4 GPa and temperatures reaching up to 530 °C. These experiments aimed to simulate geological reactions that may occur within a depth range of 340 km in subducted slabs. Raman spectroscopy was employed to monitor the reactions and microscale phenomena within the sample chamber as pressure and temperature increase. The recovered products were analyzed using scanning electron microscopy and transmission electron microscopy. The results indicate that at 0.8 GPa and 108°C, a Fischer-Tropsch Type (FTT) reaction occurred on the sample surface, resulting in the formation of organic compound formaldehyde, followed by the observation of formic acid. At higher pressures and temperatures (3.5 GPa, 420°C), the formation of γ-Fe2O3 and γ-FeOOH was observed on the sample surface, accompanied by the release of CO2 and H2. Transmission electron microscope analysis of the quenched product powders indicated that the generated iron oxides were consistent with the phases observed at high pressure and temperature conditions. High pressure and temperature dissolution experiments of siderite in water reveal that carbon may be released into the mantle wedge entirely in the form of CO2 in warm subducted slabs and cold subducted slabs that subduct to depths of 75 km. The released CO2 participates in the carbon cycle of the island arc volcanic systems in the upper mantle at depths of 70–120 km and accelerates the transfer of subducted carbon to the Earth’s surface.

Extraction of gamma iron oxide (γ-Fe2O3) nanoparticles from waste can: Structure, morphology and magnetic properties

In this work, the transformation of waste iron cans to gamma iron oxide (γ-Fe2O3) nanoparticles following acid leaching precipitation method along with their structural, surface chemistry, and magnetic properties was studied. Highly magnetic iron-based nanomaterials, maghemite with high saturation magnetization have been synthesized through an acid leaching technique by carefully tuning of pH and calcination temperature. The phase composition and crystal structure, surface morphology, surface chemistry, and surface composition of the synthesized γ-Fe2O3 nanoparticles were explored by X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Energy-dispersive X-ray spectroscopy (EDS). The XRD results confirm the cubic spinel structure having crystallite size 26.90–52.15 nm. The XPS study reveals the presence of Fe, O element and the binding energy of Fe (710.31 and 724.48 eV) confirms the formation of γ-Fe2O3 as well. By dynamic light scattering (DLS) method and zeta potential analyzer, the particle size distribution and stability of the systems were investigated. The magnetic behavior of the synthesized γ-Fe2O3 nanoparticles were studied using a vibrating sample magnetometer (VSM) which confirmed the ferrimagnetic particles with saturation magnetization of 54.94 emu/g. The resultant maghemite nanoparticles will be used in photocatalysts and humidity sensing. The net impact of the work stated here is based on the principle of converting waste into useful nanomaterials. Finally, it was concluded that our results can give insights into the design of the synthesis procedure from the precursor to the high-quality gamma iron oxide nanoparticles with high saturation magnetization for different potential applications which are inexpensive and very simple.

Stabilization of γ-Fe2O3 nanoparticles to heat by doping Nb and its property studied by Mössbauer spectroscopy

Nb5+-doped γ-Fe2O3 was synthesized by sol–gel method followed by calcination at various temperatures from 200 to 700 °C, analyzed using Powder X-ray Diffraction (PXRD), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS) and Mössbauer Spectroscopy. PXRD results show the formation of γ-Fe2O3 at 300 °C and it begins to transform to α-Fe2O3 at 350 °C for pure and 2 at.% Nb-doped samples. As the Nb doping increases (≥3.8 at.%), the transformation was suppressed up to 600 °C. TEM EDS confirms the incorporation of Nb to γ-Fe2O3 lattice in 9.1 at.% Nb sample calcined at 500 °C. At elevated temperature of 700 °C, γ-Fe2O3 went through full transformation to α-Fe2O3 by expelling large amount of Nb to the surface forming FeNbO4. TEM EDS confirms the compositional change during this process with reduced Nb content in α-Fe2O3 and Nb-rich nanoparticle on the surface of α-Fe2O3. Superparamagnetic properties were observed for Mössbauer spectra when the Nb doping increased, which is caused by decreased particle size. The slight increase in internal magnetic field also indicated the transformation from γ-Fe2O3 to α-Fe2O3. High Nb doping with 20 and 40 at.% shows the formation of FeNbO4 at lower temperature where limited or almost no Nb substitution in α-Fe2O3 was detected by EDS.

Regulating the distribution of iron active sites on γ-Fe2O3via Mn-modified α-Fe2O3 for NH3-SCR

Developing below 150 °C highly activity and broad reaction window catalysts has been challenging by using Fe-based catalysts for NH3-SCR. The octahedral Fe3+ (Fe3+Oh) sites exist in hematite (α-Fe2O3) and maghemite (γ-Fe2O3) are inactive for NH3-SCR due to the redox circle of Fe2+→Fe3+ reliance on the distribution of iron sites in crystal structure. Here we modified the α-Fe2O3 crystal structure by substituting part inactive Fe3+Oh sites with catalytically active Mn3+Oh sites, which promoted the formation of γ-Fe2O3 to generate the active tetrahedral Fe3+ (Fe3+Td) sites and enhanced the magnetism of the Fe1−yMnyOx. The strong Fe-O-Mn interaction established by crystal coordinative configurations not only boosted the formation of NO2 but also facilitated the Brønsted acid circle. Surprisingly, the Fe0.85Mn0.15Ox exhibited the superior low temperature NH3-SCR activity, with NOx conversion above 100% at 100–275 °C under a GHSV of 60000 h−1.

Biomass derived graphene like material supported Fe2O3 heterophase junction and the removal performance for phenol

Fe2O3@NC composites with different crystal forms were prepared in situ derived from biomass and Fe(NO3)3 by one-pot synthesis. In the process, biomass played important role in guiding the formation of γ-Fe2O3 beside the source of the graphene like nanosheets including N, C, O elements (NC). When the mass ratio of biomass and Fe(NO3)3 is proper, both of α- Fe2O3 and γ-Fe2O3 nanoparticles with the size of 3–10 nm deposit simultaneously on the graphene like nanosheets, forming uniform Fe2O3@NC nanosheets with the thickness of 15–30 nm. The specific area of Fe2O3@NC composite is improved drastically due to the synergistic effect between Fe2O3 nanoparticles and the graphene like nanosheets, resulting in the improvement of adsorption performance. The graphene like nanosheets as supporter of Fe2O3 nanoparticles enhance the separation and transfer of electrons and holes due to its good conductivity. On the other hand, the photoinduced electrons and holes could be separated and transferred quickly due to the effect of α-γ-Fe2O3 phase junction. Under the dual effects, the photocatalytic reaction rate constant of Fe2O3@NC composite with α-Fe2O3 and γ-Fe2O3 reaches to 1.44 × 10−3 L⋅ mg−1⋅ min−1, exhibiting far higher than pure Fe2O3 and Fe2O3@NC composite with single crystal form. Moreover, Fe2O3@NC composite could be recovered by magnet owing to the strong magnetism property of γ-Fe2O3, exhibited good reusability after five cycles by magnet recovery.

Oxidative magnetization of biochar at relatively low pyrolysis temperature for efficient removal of different types of pollutants

A novel oxidative magnetization, involving phosphomolybdic acid and Fe(NO3)3 co-promoted pyrolysis, was established to manufacture highly adsorptive magnetic biochars for adsorbing aqueous tetracycline, methylene blue, and Cr6+. The modification of phosphomolybdic acid greatly boosted the formation of γ-Fe2O3 and oxygen containing groups with enhancement of specific surface area and pore volume at 400 °C. Importantly, γ-Fe2O3 was stably fixed on surface in quasi-nanoscale. The oxidized magnetic biochar displayed 631.53, 158.45, 155.13 mg/g adsorption capabilities for tetracycline, methylene blue, and Cr6+ with 22.79 emu/g saturation magnetization, respectively. Oxygen containing groups and quasi-nanoscale γ-Fe2O3 served as key adsorption sites for these pollutants. A general oxidative magnetization was established for manufacturing high-performance magnetic biochar through phosphomolybdic acid/Fe(NO3)3 co-promoted pyrolysis at relatively low temperature.

Enhanced removal of organophosphate esters by iron-modified biochar with developed mesoporous: Performance and mechanism based on site energy distribution theory

Removing the widely concerned pollutant of organophosphate esters (OPEs) by agriculture waste biochar is an effective way to address the waste and pollutant problem simultaneously. In this work, an iron-modified coconut shell biochar (MCSB) was prepared by co-pyrolysis method and used to adsorb tris(2-chloroethyl) phosphate (TCEP) and tris(1-chloro-2-propyl) phosphate (TCPP), which were two typical OPEs. The attention was focused on comprehensively investigating the adsorption behaviors to study the adsorption mechanisms of TCEP and TCPP onto MCSB. With the development of mesoporous and formation of γ-Fe2O3 in MCSB, the adsorption equilibrium was quickly reached in 60 min with the Langmuir maximum adsorption capacities of 211.3 mg/g for TCEP and 223.7 mg/g for TCPP, respectively. Results of adsorption kinetics and isotherm showed the heterogeneous and multilayer of the adsorption process. Pore-filling interaction, the Lewis acid-base interaction, and the hydrophobic interaction were considered to drive the adsorption. And the site energy distribution theory was introduced to further reveal that the physisorption was the main adsorption mechanism, while the Lewis acid-base interaction was responsible for the differences in adsorption of TCEP and TCPP onto MCSB. Additionally, the excellent adsorption performances of MCSB in various circumstances and fixed-bed column experiments suggested that the MCSB would be a promising adsorbent for OPEs removal.

Synthesis and characterization of bar-like maghemite (γ-Fe2O3) as an anode for Li-ion batteries

In this study, bar-like maghemite (γ-Fe2O3) was obtained through the oxidation of lepidocrocite (γ-FeO(OH)) synthesized by the co-precipitation method. Afterward, the nano-bar γ-Fe2O3 performance as an anode for Li-ion batteries was studied. The formation of γ-FeO(OH) was confirmed by using Fourier transform infrared spectroscopy (FTIR). X-ray diffraction (XRD) results declared the formation of γ-Fe2O3 as a single-phase after oxidation of γ-FeO(OH) at 200 °C for 2 h. Nitrogen adsorption-desorption (BET) and high-resolution transmission microscopy (HRTEM) results revealed the formation of bar-like maghemite with a high surface area (110 m2 g−1) and an average width of about 10 nm. The anode body was prepared by tape casting of a paste prepared of bar-like maghemite. Cyclic voltammetry results disclosed the reaction path of lithium and iron oxide through charging and discharging. In addition, galvanostatic charge-discharge cycling at a current density of 500 mA g−1 presented a reversible capacity of approximately 680 mAh g−1 after 50 cycles. Moreover, the cell showed acceptable stability even at the high current charge-discharge rates of 3000 mA g−1. The good performance of the anode can be due to the size and shape of the maghemite particles. Bar-like shapes ease the expansion and contraction of particles in two-direction with less destruction imposed.

Surface Morphology and Structural Evolution of Magnetite-Based Iron Ore Fines During the Oxidation

Abstract The use of magnetite-based iron ore fines by means of fluidized bed technology has become a promising route to produce direct reduced iron. The significant influence of a prior oxidation treatment, which occurs in the preheating stage, on the subsequent fluidization and reduction behavior was observed in our previous study. As a result, it is important to investigate the oxidation of magnetite-based iron ore fines for an optimization of the proposed route. Three magnetite-based iron ore brands were analyzed. The oxidation characteristics are investigated based on thermogravimetric analysis. The surface morphology, structural evolution, and phase transformation were studied with a scanning electron microscope, an optical light microscope, and a high-temperature-X-ray diffraction (HT-XRD), respectively. The three samples showed different oxidation capacity indexes (OCIs) but similar TG-DTG curves. The oxidation rate peaks at around 330 °C and 550 °C indicated the formation of γ-Fe2O3 and α-Fe2O3. The hematite phase shows a particular growth habit. The oxidation first occurs at the surface, forming gridlike hematite structures, and then extends to the inside, resulting in hematite needles. The specific surface area and pore volume decrease significantly due to the sintering effect during oxidation.

One-step aromatic acids assisted synthesis of γ-Fe2O3 nanoparticles with large surface area by thermal decomposition of ferric nitrate

Maghemite (γ-Fe2O3) has attracted much attention due to its variety of applications in many areas. However, the current preparation methods of γ-Fe2O3 still involve complicated processes and a high cost, thereby needing improvement. In this study, a novel and facile one-step solid-state method for the preparation of γ-Fe2O3 nanoparticles (NPs) is performed through the thermal decomposition of ferric nitrate (Fe(NO3)3⋅9H2O) and the addition of aromatic acids. Three aromatic acids that have different numbers of carboxyl groups (i.e., benzoic acid, phthalic acid, and trimesic acid) are used as additives and their effects on the formation of γ-Fe2O3 NPs are investigated. Furthermore, the influence of the aromatic acid/Fe(NO3)3⋅9H2O mass ratio and calcination temperature on the structural properties of the products are investigated. The structural properties, morphology, and magnetic properties of the products are analyzed through X-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption/desorption measurements, and magnetic measurements. The results show that the addition of aromatic acids to Fe(NO3)3⋅9H2O leads to the formation of γ-Fe2O3 NPs, and has a significant influence on the morphology of γ-Fe2O3 NPs. When the aromatic acid/Fe(NO3)3⋅9H2O mass ratio is greater than 0.5, the addition of the three aromatic acids leads to the formation of pure γ-Fe2O3. The γ-Fe2O3 NPs obtained from benzoic acid/Fe(NO3)3⋅9H2O and phthalic acid/Fe(NO3)3⋅9H2O systems do not show a well-defined morphology. In contrast, the γ-Fe2O3 NPs obtained from the trimesic acid/Fe(NO3)3⋅9H2O system are composed of a porous three-dimensional hierarchical structure and have the largest Brunauer−Emmett−Teller surface area (100.0 m2 g−1).

Biomineralization of Fe3+ to Nanosized γFe2O3 by Haloferax alexandrinus GUSF-1

Hypersaline environment is a habitat with extreme osmotic conditions along with low Aw, serving as a home to extremely halophilic and halotolerant bacteria. The hypersaline environments, such as solar salterns located along the rivers, are exposed to fluxes of iron from iron ore transportation and other industrial wastes. The solar salterns often serve as a sink for metal intoxicants. Studies on archaea interaction with metal ions indicate the formation of minerals such as goethite, hematite, rhodochrosite, etc. However, studies exploring haloarchaeal candidates interacting with metals such as Fe3+ in a hypersaline growth condition are scarce. This study unveils for the first time formation of γFe2O3 from Fe3+ by the haloarchaeon, Haloferax sp. GUSF-1 thus implying the significance of the culture synthesizing minerals in hypersaline sediments. γFe2O3 is formed from Fe3+ by the haloarchaeon Haloferax sp. GUSF-1 (GenBank accession no.GU-1KF796625), under microaerophilic growth on sodium acetate. A 50 mg L−1 of Fe2+ and 30.6 mg L−1 of Fe3+ was detected inside the cells. Simultaneously, a brown-colored crystalline material deposited in the culture broth through an iron reductase inhibited by Zn2+ ions. The XRD of the deposit exhibited d values of 2.96, 2.514, 2.086, 1.6, and 1.45, while SEM-EDX displayed cubic and irregularly shaped minute particles with peaks for Fe at 0.6, 6.4, and 6.6 keV, respectively. TEM profiles revealed polycrystalline particles of 12–23 nm in size. Further, the SAED concentric pattern of light scattering with well-defined diffraction spots was consistent and matched with maghemite's crystal structure (γFe2O3). The FTIR spectrum revealed a peak at 1450 cm−1 indicating iron oxyhydroxide formation as an intermediate having γ-FeOOH stretching bond vibrations. Conclusively, this study opens the possibility of the haloarchaea isolated from solar salterns for its exploitation in nanobiotechnology.

Bovine Serum Albumin-Immobilized Black Phosphorus-Based γ-Fe2O3 Nanocomposites: A Promising Biocompatible Nanoplatform.

The interactions between proteins and nanoparticles need to be fully characterized as the immobilization of proteins onto various nanoplatforms in the physiological system often results in the change of surface of the protein molecules to avoid any detrimental issues related to their biomedical applications. Hence, in this article, the successful low-temperature synthesis of a BP-based γ-Fe2O3 (IB) nanocomposite and its interactive behavior with bovine serum albumin (BSA)—a molecule with chemical similarity and high sequence identity to human serum albumin—are described. To confirm the formation of γ-Fe2O3 and the IB nanocomposite, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy analyses of the materials were performed. Additionally, the physical interaction between BSA and the IB nanocomposite was confirmed via UV–Vis and photoluminescence spectral analyses. Finally, the biocompatibility of the BSA-immobilized IB nanocomposite was verified using an in vitro cytotoxicity assay with HCT-15 colon cancer cells. Our findings demonstrate that this newly developed nanocomposite has potential utility as a biocompatible nanoplatform for various biomedical applications.

Magnetically recoverable β-Ni(OH)2/γ-Fe2O3/NiFe-LDH composites; isotherm, thermodynamic and kinetic studies of synthetic dye adsorption and photocatalytic activity

NiFe layered double hydroxides were prepared by co-precipitation from nickel(II) nitrate hexahydrate and iron(III) nitrate nonahydrate at a pH range from 8 to 12 and subsequent hydrothermal treatment at 150 °C for 24 h. The X-ray diffraction patterns revealed that β-Ni(OH)2 and γ-Fe2O3 co-existed with a NiFe-layered double hydroxide, when prepared at pH 10, 11 and 12. The absorption band at 565 nm of the products prepared at pH 10–12 was observed together with the increase of the saturated magnetization from 0.96 emu·g−1 for NiFe-layered double hydroxide prepared at pH 8 to 12.99 emu·g−1 for NiFe-layered double hydroxide prepared at pH 12, corresponding to the formation of γ-Fe2O3. The layered double hydroxide samples possessed high adsorption capacities of Congo Red (98.6–142.4 mg·g−1) and Rhodamine 6G (46.1–97.0 mg·g−1). The adsorption of both dyes followed a Langmuir isotherm and the processes were endothermic for Congo Red and exothermic for Rhodamine 6G removals. Among the tested samples, NiFe-layered double hydroxide prepared at pH 11 exhibited the best photocatalytic degradation for Congo Red (removal of 91.1%, 10 ppm) and Rhodamine 6G (removal of 90.7%, 10 ppm) under the visible light irradiation for 5 h. According to high specific surface area (72 m2·g−1), magnetic property and stability, the β-Ni(OH)2/γ-Fe2O3/NiFe-layered double hydroxide composite could be reused as an efficient adsorbent and a photocatalyst that easily collected from the reaction.

Octyltrimethylammonium bromide-assisted synthesis of maghemite powder by thermal decomposition of ferric nitrate and its properties

Maghemite (γ-Fe2O3) powder was prepared by one-step thermal decomposition of ferric nitrate (Fe(NO3)3⋅9H2O) with the aid of octyltrimethylammonium bromide (OTAB). The effect of OTAB on the formation of γ-Fe2O3, structural properties and magnetic properties of the γ-Fe2O3 powder has been studied by X-ray powder diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, magnetic measurements and nitrogen adsorption–desorption. It is found that OTAB has a great influence on the thermal decomposition products of Fe(NO3)3⋅9H2O. With no OTAB addition, the thermal decomposition of Fe(NO3)3⋅9H2O produces only hematite (α-Fe2O3). In contrast, when OTAB is added to Fe(NO3)3⋅9H2O, a pure γ-Fe2O3 is formed, and its crystallite size can be controlled from 7.4 to 27.8 nm by varying the calcination temperature. Magnetic properties of γ-Fe2O3 powder are found to be strongly dependent on the calcination temperature. The saturation magnetization of γ-Fe2O3 powder increases from 28.6 to 67.5 emu g−1, when the calcination temperature increases from 160 to 200 °C. The sample obtained at 200 °C is nearly flake-like in shape and possesses a mesoporous structure with a Brunauer–Emmett–Teller surface area of 121.3 m2 g−1.

A study on the preparation and characterization of maghemite (γ-Fe2O3) particles from iron-containing waste materials

ABSTRACT The recovery and repurposing of valuable substances from iron-bearing wastes is challenging and vital from economic and environmental perspectives. Herein, maghemite (γ-Fe2O3) particles were synthesized from different iron-containing waste materials by simple chemical precipitation method using HCl, NaOH, and Na2CO3, followed by calcination. Subsequently, the optimum pH value for the precipitation of iron from solution, and calcination temperature for getting γ-Fe2O3 were found at 12 and 350°C, respectively. The final products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), particle size analysis (PSA), thermogravimetry/differential thermal analysis (TG/DTA), and vibrating sample magnetometry (VSM). The formation of γ-Fe2O3 was anticipated from XRD and FT-IR studies, while TG/DTA data supported their excellent thermal permanence. SEM studies showed that the γ-Fe2O3 particles were relatively irregular, mostly spherical structured with a particle size ranged around 0.2–0.35 μm. PSA confirmed the high specific surface area of γ-Fe2O3 particles, and the largest one was found from the iron dust. VSM measurement assured the existence of ferromagnetic properties in γ-Fe2O3 particles at room temperature. The findings reveal that this procedure is a viable way to prepare γ-Fe2O3 particles from iron-containing waste materials.

Facile Synthesis of Substantially Magnetic Hollow Nanospheres of Maghemite (γ-Fe2O3) Originated from Magnetite (Fe3O4) via Solvothermal Method

In the present study, we report on the successful synthesis of hollow nanospheres of maghemite (γ-Fe2O3). The γ-Fe2O3 hollow nanospheres were synthesized by annealing magnetite (Fe3O4) hexagonal nanoparticles produced by solvothermal method. Structural analysis by slow-scan X-ray diffraction (XRD) marks a small peak shift towards high angle confirming the change in the iron oxide phase from Fe3O4 to γ-Fe2O3. Further, FT-IR spectroscopy reveals for Fe3O4 a band at 571 cm−1, which shows the Fe-O stretching mode of tetrahedral and octahedral sites. Formation of γ-Fe2O3 upon annealing was again confirmed from the broadening and splitting of band 571 cm−1 into two bands, viz. 556 cm−1 and 637 cm−1. Magnetic properties of the synthesized samples were studied using a vibrating sample magnetometer (VSM) at 300 K. The value of saturation magnetization (MS) of Fe3O4 nanoparticles and γ-Fe2O3 hollow nanospheres was 56 emu/g and 43 emu/g, respectively. For Fe3O4, infrequent Verwey transition appeared when variation in magnetization with temperature was studied. Morphological analysis confirms the hexagonal shape of Fe3O4 nanoparticles with an average particle size of 57 nm. The same study interestingly epitomizes a hollow nanospherical shape with an average particle size of 12 nm for γ-Fe2O3. The emergence of the Verwey transition in Fe3O4 hexagonal nanoparticles and the existence of significant magnetization of 43 emu/g in hollow nanospheres of γ-Fe2O3 in this study are contentious and fascinating for possible applications.

Acid Red 66 Dye Removal from Aqueous Solution by Fe/C-based Composites: Adsorption, Kinetics and Thermodynamic Studies.

The presence of synthetic dyes in water causes serious environmental issues owing to the low water quality, toxicity to environment and human carcinogenic effects. Adsorption has emerged as simple and environmental benign processes for wastewater treatment. This work reports the use of porous Fe-based composites as adsorbents for Acid Red 66 dye removal in an aqueous solution. The porous FeC and Fe/FeC solids were prepared by hydrothermal methods using iron sulfates and sucrose as precursors. The physicochemical properties of the solids were evaluated through X-ray diffraction (XRD), Scanning electron microscopy coupled with Energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared s (FTIR), Raman and Mössbauer spectroscopies, nitrogen adsorption–desorption isotherms, Electron Paramagnetic Resonance (EPR) and magnetic saturation techniques. Results indicated that the Fe species holds magnetic properties and formed well dispersed Fe3O4 nanoparticles on a carbon layer in FeC nanocomposite. Adding iron to the previous solid resulted in the formation of γ-Fe2O3 coating on the FeC type structure as in Fe/FeC composite. The highest dye adsorption capacity was 15.5 mg·g−1 for FeC nanocomposite at 25 °C with the isotherms fitting well with the Langmuir model. The removal efficiency of 98.4% was obtained with a pristine Fe sample under similar experimental conditions.

Effect of Concentrations of Fe2+ and Fe3+ on the Corrosion Behavior of Carbon Steel in Cl− and SO42− Aqueous Environments

The concentration of metal ions in aqueous environments significantly affects the formation of corrosion products and further metal corrosion. In this paper, the electrochemical behavior of carbon steel in the presence of Fe2+ or Fe3+ concentration in Cl− and SO42− aqueous environments have been investigated using conventional electrochemical methods such as linear polarization and alternating current impedance spectroscopy. The morphology and composition of carbon steel corrosion products were studied using scanning electron microscopy and laser Raman spectroscopy. The effects of corrosion products and iron ions concentration on the corrosion of carbon steel were discussed. Corrosion products of carbon steel in aqueous environments were γ-FeOOH, γ-Fe2O3 and a small amount of α-Fe2O3. The addition of Fe2+ affected the cathode reaction of the electrode reaction, and promotes the formation of γ-FeOOH and Fe3O4. And with the increase of Fe2+ concentration in the solution, the anode process of electrode reaction was suppressed. The addition of Fe3+ promoted the formation of γ-Fe2O3 and Fe3O4. Fe3+ affected the ionization of water, causing the pH of the solution to drop. Fe3+ undergoes a redox reaction with the matrix. Addition of Fe3+ ions promoted the formation of FeOOH, an intermediate product, which reacts with the anode product Fe2+. These factors all accelerated the corrosion process.

Thermal and Magnetic Properties of Maghemite γ-Fe2O3 Synthesized by a Precursor Method

Low-dimension ferromagnetic maghemite γ-Fe2O3 was synthesized through a precursor route, using basic iron formate Fe(OH)(HCOO)2 as a precursor. Conditions of formation of γ-Fe2O3 and the temperature range of its existence on heating in air were determined. The saturation magnetization of γ-Fe2O3 produced through heating the precursor at 350°C 57.5 (T = 4.2 K) and 43.8 emu/g (T = 300 K).

Ultrasound-assisted synthesis and catalytic activity of mesostructured FeOx/SBA-15 and FeOx/Zr-SBA-15 catalysts for the oxidative desulfurization of model diesel

Abstract Two series of FeOx/SBA-15 and FeOx/Zr-SBA-15 mesoporous catalysts were synthesized with ultrasound-assisted method by varying Fe content from 10 wt% to 20 and 30 wt%. The crystalline structure, textural properties, surface morphologies, surface acidity, and phase composition of the catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM), in situ Fourier transform infrared spectroscopy (FTIR). The XRD, Raman and Mossbauer spectroscopic characterizations showed that both γ-Fe2O3 and α-Fe2O3 nanoparticles were present in all the catalysts and Fe3+ ions were dispersed on the surface of SBA-15 with different coordination. In the oxidation desulfurization (ODS) of a model diesel, the reaction parameters (temperature, time, and catalyst mass), Fe content, zirconium doping, and surface acidity of the catalysts were all critical for the ODS in a biphasic reaction system. All catalysts chiefly contained Lewis acidity which was related to iron content and zirconium modification and could correlate well with catalytic activity. Zirconium incooperating into the SBA-15 solid increased surface acidity and promoted γ-Fe2O3 formation by inhibiting the amorphous iron oxide in the Fe/Zr-SBA-15 catalysts, thus improved the ODS efficiency. The reaction temperature 60 °C was the optimal for ODS reaction, temperature greater than 80 °C led to oxidant partial decomposition. Under the optimal reaction condition, 0.1 g of the best catalysts (30%Fe/SBA-15 and 30%Fe/Zr-SBA-15) could remove all dibenzothiophene (DBT) (300 ppm DBT in 100 ml n-hexadecane) at 60 °C within 30 min. Thus, the combination of catalysis, oxidation and extraction in our polar-nonpolar-solid reaction system was simultaneously realized in one unit, which will be promising for effectively removal of organosulfur compounds for production of ultralow sulfur fuels.