Iron Oxide Precursor Research Articles

Bergera koenigii stem-derived magnetic biochar nanocomposite for enhanced photocatalytic efficiency of Ce1-xZnxO2-δ NPs under UV light for the degradation of methyl orange

The production of mesoporous, nanocrystalline, Zn-doped CeO2 nanoparticles (NPs) at various concentrations of Zn, Magnetic biochar (MBC)-Zn-doped CeO2 nanocomposites (NC), their characterizations, and photocatalytic degradation analysis are presented in this study. The synthesis of MBC-Ce0.91Zn0.09O2-δ NC is based on the carbonization of an iron oxide precursor with powdered Bergera koenigii stem (curry leaf stem). XRD and TEM results confirm polycrystalline, spherical fluorite Ce1-xZnxO2-δ NPs and MBC-Ce0.91Zn0.09O2-δ NC formations. The crystallite size varies from 4–12 nm with an increase in the doping concentration of Zn and 8.55 nm for MBC-Ce0.91Zn0.09O2-δ NC. XPS analysis displays the valence states and surface chemical composition of the as-prepared MBC-Ce0.91Zn0.09O2-δ sample. BET analysis provides the surface area (17–32 m2/g for Ce1-xZnxO2-δ NPs and 142 m2/g for MBC-Ce0.91Zn0.09O2-δ NC) and pore size (25–45 Å for Ce1-xZnxO2-δ NPs and 17.35 Å for MBC-Ce0.91Zn0.09O2-δ NC) of all the samples. All the samples possess good UV absorption in the range of 200–400 nm, and the bandgap energy of the as-prepared samples decreased from 3.088 to 2.79 eV with increased dopant concentration and on-load magnetic biochar. The oxygen deficiencies and lattice deformations of the as-prepared samples are studied using Raman, FTIR, and photoluminescence (PL) spectra. The degradation efficiency of 5 ppm Methyl Orange (MO) is analyzed using 50 mg catalytic (Ce1-xZnxO2-δ NPs, MBC-Ce0.91Zn0.09O2-δ NC) dosage by maintaining the pH of the solution as 4. After 16 min of UV irradiation, the as-synthesized Ce0.91Zn0.09O2-δ NPs and MBC-Ce0.91Zn0.09O2-δ NC exhibit 91 % and 97 % decolorization and 90 % and 94 % total organic carbon (TOC) removal efficiency. Regression analysis is performed to evaluate each model's applicability to photocatalytic degradation. The regeneration experiments on Ce0.91Zn0.09O2-δ NPs and MBC-Ce0.91Zn0.09O2-δ NC prove the stability of these catalysts for activating MO.

Removal of metronidazole from simulated wastewater using Fe/C catalyst with a combination of heterogenous Fenton and ozonation

This study examined roles of iron oxide/porous carbon material (Fe/C) for removing metronidazole in simulated wastewater by adsorption and then followed by a degradation using advanced oxidation process (H2O2, O3 and combination of H2O2/O3). Fe/C was produced by an impregnation of iron oxide precursors during resorcinol-formaldehyde synthesis followed by pyrolysis at 800 °C. For comparison, blank carbon (without iron loading) was also synthesized. The properties of porous carbon were investigated by SEM-EDX and N2-sorption analyzer. Blank carbon and Fe/C featured the specific surface area of 755 m2g-1 and 394 m2g-1, respectively. The loading of iron oxide altered the pore structures of material. The adsorption isotherm data were followed by the Langmuir isotherm model with metronidazole uptake up to 46.07 mg g-1 and 39.97 mg g-1 at 30oC by Fe/C and blank carbon. The degradation study was then carried out with catalyst dosage of 0.1 g/100 mL solution and 120 min reaction time at 30 oC. It is noticeably that, the degradation of metronidazole was better when a combination of H2O2/O3 was employed, compared with an individual of H2O2 or O3. Regarding the stability, Fe/C maintained its high activity upon four consecutive runs.

Enhanced photocatalytic activity of CeO2 and magnetic biochar-CeO2 nanocomposite prepared from Murraya koenigii stem for degradation of methyl orange under UV light

This paper discusses the synthesis and characterization of CeO2 nanoparticles (NPs), magnetic biochar-CeO2 (MBC-CeO2) nanocomposites (NCs), and their photocatalytic analysis in methyl orange (MO) degradation. MBC-CeO2 material is synthesized on the basis of carbonization of iron oxide precursor treated with Murraya koenigii (curry leaf) stem powder. CeO2 with crystallite size 7.78 nm and MBC-CeO2 with crystallite size 14 nm are identified from XRD, with band gap energies 3.16 and 2.84 eV respectively. XPS, SEM, TEM, BET, UV–visible, FTIR, and PL characterizations are conducted to study the morphology, oxygen vacancy concentration in the samples. The removal efficiency of Methyl Orange (MO) is studied by changing both pH and concentration of MO solution. The decolorization of MO is observed at an optimum level of pH 4, with a catalyst dosage of 50 mg, which obeys pseudo-first-order kinetic theory. Under 16 min UV irradiation treatment, the decolorization efficiency of the as-prepared MBC-CeO2 is 96.7 % and total organic carbon (TOC) is ∼94 %, and for the as-prepared CeO2 it is 87.5 % and ∼ 81 % respectively. The plausible degradation pathway of MO is analyzed through LC-MS method. Regression studies are conducted to assess the suitability of all models towards photocatalytic degradation. The recycling experiment showed that both MBC-CeO2 and CeO2 are excellent stable catalysts for the activation of MO.

Preparation and Use of Iron on Carbon Foam for Removal of Organic Dye from Water: Batch Studies.

The presence of dyes in effluents from textile industries has a detrimental effect on aquatic ecosystems as it hinders the process of photosynthesis by reducing the penetration of sunlight. The adsorption capacity of a carbon foam-based iron oxide sorbent obtained from natural sources for the removal of organic methylene blue (MB) dye from water was investigated. The adsorption capacities were examined by batch experiments, wherein the impacts of varying iron content, sorbent dosage, contact time, dye concentration, and characterization were assessed. The physical characteristics and surface morphology of the synthesized carbon foam were also investigated. The carbon precursor and iron oxide precursor were coalesced within a singular container and subjected to carbonization process. This resulted in the formation of a porous structure that is capable of effectively providing support to the iron oxide particles. The carbon foam produced is a self-assembled formation that possesses the characteristic shape and underlying network structure reminiscent of bread. As the number of nanoparticles went up, so did the number of active sites. At elevated temperatures, the interactions between the dye molecules were enhanced, resulting in a more efficient process of dye removal. The magnetite sample exhibited endothermic adsorption, and all other samples exhibited exothermic adsorption. The adsorption of MB onto iron supported by carbon foam did not exhibit intraparticle diffusion as the only rate-limiting step for all samples. The adsorption rate was governed by a multistep elementary reaction mechanism in which multiple processes occurred simultaneously. The experimental data in this study may be accurately modeled by the pseudo-second-order kinetic model (R2 > 0.96). Additionally, the Freundlich isotherm best describes the adsorption equilibrium, which is supported by the outstanding fit of data to the model (R2 > 0.999). The findings suggest that the utilization of a natural carbon foam as a support for an immobilized iron oxide sorbent demonstrates considerable effectiveness in the removal of methylene dye from industrial effluent.

Size Control of Iron Oxide Nanoparticles Synthesized by Thermal Decomposition Methods

The controlled synthesis of superparamagnetic iron oxide nanoparticles is crucial for a variety of biomedical applications. Among different synthesis routes, thermal precursor decomposition methods are the most versatile, yielding monodisperse nanoparticles on the multigram scale. Recent in situ kinetic studies of the nucleation and growth processes during thermal decomposition routes revealed nonclassical nucleation and growth paths involving amorphous precursor phases and aggregative growth steps. With the knowledge of this kinetic mechanism, we systematically examined a range of different iron oxide heat-up synthesis routes to understand and conclude which methods allow good and reproducible size control over a range of relevant nanoparticle diameters. Using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) for the characterization of the nanoparticle size distribution, we find that a set of solvents (1-octadecene, trioctylamine, docosane) provides access to a temperature range between 300 and 370 °C, allowing us to synthesize monodisperse nanoparticles in a size range of 6–24 nm on a large scale. We confirm that a thermal pretreatment of the iron oxide precursor is essential to achieve reproducible size control. We find that each solvent provides access to a certain temperature range, within which the variation of temperature, heating rate, or precursor concentration allows us to reproducibly control the nanoparticle size.

Synthesis of novel carbon-supported iron oxide sorbents for adsorption of dye from aqueous solutions: equilibrium and flow-through studies

Textile effluents contain dyes that negatively affect water bodies and inhibit photosynthesis by reducing sunlight penetration. This study investigated the adsorption capacity of an iron oxide sorbent immobilised on naturally derived carbon foam for the removal of organic methylene blue dye from water. In this study, the carbon precursor and iron oxide precursor were mixed and carbonised in a single vessel. Baking and carbonization of the natural grain combination produce a porous structure that can act as an effective support for the iron oxide particles. The carbon foam prepared had a self-assembled structure with flour as a basic element. Sorbents of 6 weight (wt)%, 15 wt% iron, and a 0 wt% iron control sample were prepared. Transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) techniques were used to examine the synthesised carbon foam physical properties and surface morphology. The adsorption capabilities were investigated in batch tests by determining the effects of an increase in iron content, sorbent dosage, contact time, and dye concentration. Breakthrough curves were obtained by varying the height of the sorbent bed and varying the flowrate of the dye solution. A higher bed height corresponds to a greater amount of adsorbent. The breakthrough and equilibrium adsorption capacities were found to increase with increasing bed height. When the flow rate is high, the dye solution leaves the column before equilibrium, resulting in shorter breakthrough and saturation times. Higher bed heights and lower flow rates resulted in optimal dye removal in the flow through the system. Breakthrough time increases with increasing iron content. The 15 wt% iron sample displayed superior adsorption capabilities than the 6 wt% sample, while the 0 wt% iron control sample displayed minimal adsorptive capabilities. The pseudo-first order kinetic model was the best fit model for this study (R2 > 0.96), and the adsorption equilibrium is best described by the Freundlich isotherm (R2 > 0.99). The results showed that an iron oxide sorbent immobilised on carbon foam made from natural sources is a good adsorbent for removing methylene dye.

Fly ash waste-derived Fe@Fe3O4 core-shell nanoparticles for acetic acid ketonization

Iron oxide is a cost-effective catalyst for the ketonization of carboxylic acid components of bio-oil crude derived from the pyrolysis of lignocellulosic biomass. Fly ash (FA) waste from coal-fired power plants is an abundant source of iron oxide precursors. Here we report the reductive thermal processing of hematite derived from acid-leached fly ash. Annealing of the hydroxide precipitated leachate produces nanoparticulate α-Fe2O3 containing ∼10 wt% metal impurities (principally Al, Mg, Ca and Ti). Subsequent extended (5 h) reduction under H2 at 400 °C generates a Fe@Fe3O4 core-shell structure, and is accompanied by surface segregation of Al, Mg, Ca and Ti as their oxides, a decrease in particle size, and the concomitant formation of surface oxygen vacancies. These physicochemical changes increase the surface area and introduce Brønsted basicity alongside the intrinsic Lewis acidity of the non-stoichiometric magnetite, promoting ketonization through synergistic activation of two acetic acid molecules. The specific activity of the 5 h reduced FA derived catalyst (FA-5 h) was 3.9 mmol·g−1·min−1 at 400 °C, with a corresponding turnover frequency per acid site of 14.3 min−1. In-situ DRIFTS reveals acetic acid dissociatively adsorbs over FA-5 h, adopting a bidentate acetate binding mode identical to that for commercial magnetite, albeit the fly ash derived catalyst stabilises acetate to a higher temperature (∼300 °C) facilitating C-C coupling versus desorption. Successive doping of commercial magnetite by low concentrations of Al, Mg, Ca and Ti, and subsequent reduction, generated a model catalyst whose acid-base properties and ketonization activity reproduced those of FA-5 h. Surface segregated dopants, notably Ti, are largely responsible for the high activity of FA-5 h through the introduction of additional acid and base sites for acetic acid ketonization.

Solid phase-fabrication of magnetically separable Fe3O4@graphene nanoplatelets nanocomposite for efficient removal of NSAIDs from wastewater. Perception of adsorption kinetics, thermodynamics, and extra-thermodynamics

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most detected pharmaceuticals in wastewater and likely pass to drinking water. Magnetic nanocomposite has been greenly fabricated for removal of different NSAIDs; ibuprofen (IP), ketoprofen (KP), naproxen (NX), and diclofenac sodium salt (DF); from wastewater. Solid-phase fabrication of the magnetically separable nanocomposite has been optimized using iron oxide (Fe3O4) and graphene nanoplatelets (GNP) precursors. The characterization showed the homogenous distribution of the magnetite over the GNP with a high specific surface area. Different parameters having a potential influence on the removal of the NSAIDs from wastewater by the Fe3O4@GNP nanocomposite were studied and optimized for efficient performance that achieves adsorption capacities of 8.76, 10.6, 14.3, and 7.63 mg/g for KP, NX, DF, and IP, respectively (296 K). The adsorption of the four NSAIDs by the Fe3O4@GNP nanocomposite followed pseudo-second-order kinetics, and it is mainly controlled by the intraparticle diffusion process. The thermodynamic and extra-thermodynamic studies demonstrated that the adsorption is endothermic and is affected by enthalpy-entropy compensation. The molecular interactions of the four drugs with the nanocomposite have been explored. Successful application of the nanocomposite for fast and efficient removal of the NSAIDs from wastewater has been accomplished with an average removal of 71.0%.

Magnetically-separable photocatalyst of magnetic biochar from snake fruit peel for rhodamine B photooxidation

Magnetically-separable photocatalyst of magnetic biochar has been prepared from snake fruit peel and utilize for photooxidation of rhodamine B. The synthesis was performed by immobilizing iron oxide precursors via co-precipitation followed by carbonization under N2 gas at 400 °C for h. The obtained magnetic biochar was characterized using X-ray diffraction, scanning electron microscopy-energy dispersive x-ray spectroscopy, UV–visible diffuse reflectance spectroscopy, transmission electron microscopy, x-ray photoelectron spectroscopy, and gas sorption analysis. The results from XRD analysis showed that magnetic biochar composed as the dispersed Fe3O4 nanoparticles with slightly γ- Fe2O3 phase. TEM analysis concluded that the particle size is ranging at 5–20 nm. Photocatalytic activity studies of MBC were performed for rhodamine B photooxidation at various pHs and H2O2 concentrations. Photooxidation of rhodamine B followed second-order kinetics at the optimum pH of 7 and H2O2 concentration of 0.5% with the degradation efficiency of 99.9%. Insignificant change of degradation efficiency until fifth cycle indicated that magnetic biochar has stability and potential to be applied in larger scale.

Stable and magnetically separable nanocomposite prepared from bauxite mining tailing waste as catalyst in wet peroxidation of tetracycline

The purpose of this study is to convert bauxite mining tailing waste into magnetic nanocomposite as catalyst in catalytic wet peroxidation of tetracycline. The preparation of material was performed via hydrothermal method of immobilized iron oxide precursor of Fe2+ and Fe3+ in alkaline condition, followed by calcination. The obtained nanocomposite was characterized using X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and vibration sample magnetometer. The results from XRD, XPS and TEM analyses showed that the composite composed as the dispersed γ-Fe2O3 in combination with Fe3O4 nanoparticles. The catalytic activity studies of the nanocomposite showed the capability of material to remove tetracycline with supportive adsorption capability. The oxidation of tetracycline was recorded to follow pseudo-first kinetics with removal efficiency of 89.7 % for 20 ppm of tetracycline. Insignificant change of removal efficiency at varied tetracycline concentration ranging at 2–40 ppm indicated its potential to be active in wide range of concentration. In addition, the nanocomposite showed stability as studied by XRD analysis along with the easy in separation as the magnetic properties with magnetism of 9.8 emu/g.

Effects of Biologically Synthesized Iron Oxide Nanoparticles on Rhizospheric Microorganisms Associated with Tomato (Solanum lycopersicum L.)

In this study, the effect of iron oxide nanoparticles on soil rhizospheric microbial communities of tomato was investigated. Iron oxide nanoparticles were biologically synthesized using plant extract from Azadirachta indica, and characterized using a UV-VIS spectrophotometer. Varying concentrations (25, 50, 75, or 100 %) of biosynthesized iron oxide nanoparticles or precursor solution was rhizoinjected into soils in which tomato plants were grown. Plate count method was used to analyse population size and community structure of test subjects. Quantitative analysis of the bacterial and fungal community was determined and diversity indicies were calculated. The results obtained from the analysis revealed that the addition of iron oxide nanoparticles to the soil changed bacterial and fungal community with respect to the control. Also, the bacterial and fungal abundance were changed. Some tolerant microorganisms such as Micrococcus, Stapylococcus, Aspergillus, Trichoderma and Penicillium could withstand high concentrations of iron oxide nanoparticles. Shannon diversity indices showed that there was difference in the diverisity of each concentration of iron oxide nanoparticles for both fungal and bacterial communties. The study's findings showed that high concentration of iron oxide nanoparticles in the soil had adverse effect on both the tomato and the microorganisms associated with the root of the tomato. Further study needs to be conducted to ascertain the magnitude of impact iron oxide nanoparticles will have on plants and rhizosphere microbiome.

Synthesis by spray pyrolysis of gold nano species confined in iron oxide nanospheres effective in the reduction of 4-nitrophenol to 4-aminophenol

The highly effective Au/Fe2O3-@Au/Fe2O3 nanoreactors for the 4-nitrophenol (4-NP) reduction are successfully obtained by one-pot synthesis using the spray pyrolysis (SP) technique. The Au/Fe2O3-@Au/Fe2O3 nanoreactors manifest superior catalytic activity in the reduction of 4-NP in the presence of sodium borohydride (NaBH4) compared to gold-iron oxide nanoreactors prepared via a colloidal approach. The negative effect of the reaction product accumulation, the 4-aminophenol (4-AP), on the catalytic reduction of 4-NP over Au/Fe2O3-@Au/Fe2O3 is examined by a direct pre-injection of 4-AP to the reaction media. To the best of our knowledge, it is the first experimental evidence of gold active sites blocking by 4-AP. All obtained samples are characterized by the yolk-shell spherical hollow structure mainly consisted of two embedded hollow nanospheres. The reduction of iron oxide precursor concentration diminishes the diameter of final iron oxide nanospheres. According to STEM-EDS analysis and STEM, Au nano species are uniformly dispersed on both iron oxide nanospheres. The SP technique presently used to synthesize Au/Fe2O3-@Au/Fe2O3 nanoreactors manifests high potential for the one-pot fabrication of a large variety of nanoreactors with various active materials applied as heterogeneous catalysts in numerous catalytic processes.

Synthesis of a High-Capacity α-Fe2O3@C Conversion Anode and a High-Voltage LiNi0.5Mn1.5O4 Spinel Cathode and Their Combination in a Li-Ion Battery.

A Li-conversion α-Fe2O3@C nanocomposite anode and a high-voltage LiNi0.5Mn1.5O4 cathode are synthesized in parallel, characterized, and combined in a Li-ion battery. α-Fe2O3@C is prepared via annealing of maghemite iron oxide and sucrose under an argon atmosphere and subsequent oxidation in air. The nanocomposite exhibits a satisfactory electrochemical response in a lithium half-cell, delivering almost 900 mA h g–1, as well as a significantly longer cycle life and higher rate capability compared to the bare iron oxide precursor. The LiNi0.5Mn1.5O4 cathode, achieved using a modified co-precipitation approach, reveals a well-defined spinel structure without impurities, a sub-micrometrical morphology, and a reversible capacity of ca. 120 mA h g–1 in a lithium half-cell with an operating voltage of 4.8 V. Hence, a lithium-ion battery is assembled by coupling the α-Fe2O3@C anode with the LiNi0.5Mn1.5O4 cathode. This cell operates at about 3.2 V, delivering a stable capacity of 110 mA h g–1 (referred to the cathode mass) with a Coulombic efficiency exceeding 97%. Therefore, this cell is suggested as a promising energy storage system with expected low economic and environmental impacts.

Influence of Phase Composition and Pretreatment on the Conversion of Iron Oxides into Iron Carbides in Syngas Atmospheres

CO2 Fischer–Tropsch synthesis (CO2–FTS) is a promising technology enabling conversion of CO2 into valuable chemical feedstocks via hydrogenation. Iron–based CO2–FTS catalysts are known for their high activities and selectivities towards the formation of higher hydrocarbons. Importantly, iron carbides are the presumed active phase strongly associated with the formation of higher hydrocarbons. Yet, many factors such as reaction temperature, atmosphere, and pressure can lead to complex transformations between different oxide and/or carbide phases, which, in turn, alter selectivity. Thus, understanding the mechanism and kinetics of carbide formation remains challenging. We propose model–type iron oxide films of controlled nanostructure and phase composition as model materials to study carbide formation in syngas atmospheres. In the present work, different iron oxide precursor films with controlled phase composition (hematite, ferrihydrite, maghemite, maghemite/magnetite) and ordered mesoporosity are synthesized using the evaporation–induced self–assembly (EISA) approach. The model materials are then exposed to a controlled atmosphere of CO/H2 at 300 °C. Physicochemical analysis of the treated materials indicates that all oxides convert into carbides with a core–shell structure. The structure appears to consist of crystalline carbide cores surrounded by a partially oxidized carbide shell of low crystallinity. Larger crystallites in the original iron oxide result in larger carbide cores. The presented simple route for the synthesis and analysis of soft–templated iron carbide films will enable the elucidation of the dynamics of the oxide to carbide transformation in future work.

Enhanced performance of magnetic montmorillonite nanocomposite as adsorbent for Cu(II) by hydrothermal synthesis

Magnetic montmorillonite nanocomposites of Fe3O4/Mt were synthesized via a hydrothermal method. The syntheses were conducted by dispersing iron oxide precursors (FeSO4 and FeCl3) in montmorillonite in the Fe content range of 10–50 wt%. The properties of the nanocomposites were investigated by X-ray diffraction, gas sorption analysis, scanning electron microscopy-energy dispersive spectroscopy, transmission electron microscopy, and vibration sample magnetometer measurements. The kinetics and isotherms for Cu(II) adsorption by the nanocomposites were evaluated. The results showed that the iron oxide in the nanocomposite was in the form of Fe3O4, with a particle size of 10–60 nm, where the particle size is smaller than that produced by the co-precipitation method. The nanocomposites displayed good Cu(II) adsorption capacity and easy separation owing to the magnetic properties. The kinetics of Cu(II) adsorption followed a pseudo–second–order kinetic model and fit to the Langmuir model, with a maximum uptake of 154.45 mg g−1 over the nanocomposite containing 30 wt%. Fe. The kinetics, FTIR study and X-ray photoelectron spectroscopy investigation revealed that the adsorption mechanism was influenced by the specific surface area, magnetism, and reduction-oxidation mechanism on the surface of the nanocomposite. Furthermore, the nanocomposites demonstrated chemical stability, given that the adsorption capacity was maintained after five cycles.

Oil-absorbent MnOx capped iron oxide nanoparticles: Synthesis, characterization and applications in oil recovery

In this study, we synthesized core-shell γ-Fe2O3/MnOx magnetic nanoparticles with core diameter of ~31 ± 3 nm and saturation magnetization ranging from 55 to 70 emu/g, using an inexpensive, facile and environmentally friendly approach. The synthesis is done through acid catalyzed reduction of KMnO4 and carboxymethyl cellulose (CMC) capped iron oxide in water. The synthesized particles were characterized by X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometer, Fourier transform infrared spectroscopy, thermo gravimetric analysis and differential scanning calorimeter. The continuous oxidation of carboxymethyl cellulose on Fe3O4 in the presence of KMnO4 enabled the formation of MnOx shell. The thickness of MnOx shell is tuned by varying the amount of acid and the ratio of KMnO4: iron oxide precursor. The shell thickness increased from ~2.9 nm to 4.6 nm with increase in HCl concentration because of rapid formation of large number of nuclei and their deposition on iron oxide. Interestingly, MnOx shell was amorphous at lower [H+] but was crystalline at higher [H+]. The magnetic particles with amorphous MnOx nanoshell showed superior stability for a range of pH. A change in particle morphology is (flower to square shaped) due to the competitive adsorption of oxidized organic products of carboxymethyl cellulose polymer and MnOx nuclei at higher temperature, and the higher Gibbs free energy of the flower shaped particles. XPS results show that the iron oxide coated with CMC has 2:3 relative concentration of the Fe2+:Fe3+ ions, while oxidation state of Fe in MnOx capped one was +3. The percentage of hydroxyl group content decreased from 14 to 11% when the Fe3O4:KMnO4 ratio was changed from 1:0.2 to 1:0.5 due to the change in Mn3+:Mn4+ ratio. It is hypothesized that oil sorption occur through exchange of surface hydroxyl groups on MnOx shell. The oil removal efficiency of the prepared particle was >93% after six cycles.

A Gas Sensor With Fe2O3 Nanospheres Based on Trimethylamine Detection for the Rapid Assessment of Spoilage Degree in Fish.

A spherical iron oxide precursor was prepared using a solvothermal method, and then treated thermally at 400°C to obtain α-Fe2O3 nanoparticles. The structures and morphology of the as-obtained products were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results showed that the diameter of the α-Fe2O3 nanoparticles was approximately 500 nm. In addition, we formed the α-Fe2O3 nanoparticles into a thick film as a gas sensor and performed a gas sensing test. When the working temperature was set at 250°C, the α-Fe2O3 nanoparticle displayed very good selectivity and high sensitivity for trimethylamine (TMA). The minimum detection was as low as 1 ppm, and the response value for 100 ppm TMA gas was 27.8. Taken together, our findings illustrated that the α-Fe2O3 nanoparticles could be used as a gas-sensitive material to test the freshness of fish.

Preparation and Properties of Iron Oxide Doped Mesoporous Silica Systems

In present paper synthetic conditions and properties of mesoporous silica materials containing magnetic iron oxides (γ-Fe2O3, Fe3O4) have been studied. Two synthetic routs have been considered in detail. The first sample series has been prepared by template hydrothermal synthesis via co-condensation of silica and iron oxide (HT). The second sample series has been prepared via intercalation of γ-Fe2O3 nanoparticles into an MCM-48 silica matrix (PM). For these materials specific surface, pore volume, pore and particle sizes have been determined. The relationship of the synthetic method, [Si]/[Fe] ratio, phase composition of the materials and their textural and structural characteristics has been established. Phase composition of the samples was determined by X-ray diffraction (XRD) method. In the samples of FexOy–SiO2 with the component ratios [Si]/[Fe] = 0.4–0.6 synthesized by the HT method, maghemite (γ-Fe2O3) has been found to be the main phase of iron oxide component. For preparation of these samples a solution of FeSO4 and FeCl3 with a molar ratio of 1:1 was used as an iron oxide precursor. According to XRD data γ-Fe2O3 phase is present in all the samples of FexOy–SiO2, obtained by the PM method. Magnetic properties of the both sample series have been studied in the temperature range 4–300 K. According to the hysteresis curves, the sample FexOy–SiO2 ([Fe]/[Si] = 0.6), obtained by the HT method, has been found to be a typical ferromagnetic. The sample with the same oxide ratio obtained by the PM method demonstrated a ferrimagnetic behavior.

Facile synthesis and characterization of high-purity α″-Fe16N2/SBA-15 mesoporous nanocomposites via a template-assisted method

Typical synthesis of α″-Fe16N2 nanoparticles involves nitridation of iron nanoparticles obtained from the reduction of iron oxide, during which the iron nanoparticles are prone to agglomerate and make the nitridation difficult. Herein, we report a method to obtain α″-Fe16N2 phase by loading the iron oxide (hematite, α-Fe2O3) precursors in the channels of the ordered mesoporous silica (SBA-15), and the α-Fe2O3/SBA-15 was prepared by means of a facile impregnation and calcination method. The results showed that the nitridation efficiency was greatly improved than previous reports and high α″-Fe16N2 content (∼92 wt%) was synthesized at 160 °C for 8 h. Transmission electron microscopy and N2 adsorption-desorption characterizations demonstrate that the as-synthesized α″-Fe16N2/SBA-15 nanocomposites maintained the ordered hexagonal mesoporous structures, and α″-Fe16N2 was successfully filled inside the mesochannels of SBA-15, indicating the SBA-15 has taken great effect in the remarkable increasement of nitridation efficiency.

The Preparation of Iron Oxide Nanoparticles by a Self-combustion Method

This paper deals with problematic of preparation of iron oxide nanoparticles according to a self-combustion method. Iron oxide nanoparticles can be used e.g. for catalysators and gas sensors or in MRI. The Self-combustion method is based on rapid chemical reaction between a fuel and iron oxide precursor. Glycine, urea and citric acid were used as fuels and iron nitrate nonahydrate was used as an iron oxide precursor. The self-combustion method doesn't require any special equipment, is environment-friendly due to minimize pollution and the results are easily reproducible. The shape, size, and phase of resulting particles were investigated studied using scanning electron microscopy and energy-dispersive analysis.