Aqueous Solution Of Iron Nitrate Research Articles

Eggshell-Mediated Hematite Nanoparticles: Synthesis and Their Biomedical, Mineralization, and Biodegradation Applications

The present study demonstrates the synthesis of phase pure hematite (α-Fe2O3) nanoparticles (NPs) using collagen protein and calcium carbonate extracted from eggshell membranes and eggshells, respectively, as organic additives. To test the influence of organic additives on the quality of the resulting NPs, the amount of eggshell powder was varied between 1 to 5 g in aqueous iron nitrate solution. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and RAMAN analysis confirmed the formation of hematite NPs without any impurities. FTIR spectra revealed the presence of polyphenolic constituents on the surface of the resulting NPs as stabilizers, which may potentially be responsible for the observed antioxidant and antibacterial properties. Furthermore, the stable phase and the presence of low defects divulged the high hardness value (~983 HV) and fracture toughness (8.59 MPa m1/2), which can be exploited for bone implantation. The FE-SEM results demonstrate the formation of spherical particles, which are well-separated NPs. The results of a biodegradation study which was carried out in phosphate-buffered saline (PBS) revealed that the as-prepared NPs retained their hardness even after 72 h of soaking. These prepared NPs showed 95% radical scavenging activity (RSA) and were good carriers against S. aureus bacteria. Moreover, the SEM images of the mineralization of iron oxide NPs confirmed the formation of new bone. After 5 weeks, all pores were filled, and the minerals were deposited on the surfaces of the scaffolds.

The Size Dependence of Microwave Permeability of Hollow Iron Particles.

Hollow ferromagnetic powders of iron were obtained by means of ultrasonic spray pyrolysis. A variation in the conditions of the synthesis allows for the adjustment of the mean size of the hollow iron particles. Iron powders were obtained by this technique, starting from the aqueous solution of iron nitrate of two different concentrations: 10 and 20 wt.%. This was followed by a reduction in hydrogen. An increase in the concentration of the solution increased the mean particle size from 0.6 to 1.0 microns and widened particle size distribution, but still produced hollow particles. Larger particles appeared problematic for the reduction, although admixture of iron oxides did not decrease the microwave permeability of the material. The paraffin wax-based composites filled with obtained powders demonstrated broadband magnetic loss with a complex structure for lesser particles, and single-peak absorption for particles of 1 micron. Potential applications are 5G technology, electromagnetic compatibility designs, and magnetic field sensing.

Relationship between the Photoluminescence Spectra and IR Spectroscopy of Mesoporous Silicon Samples during Long-Term Storage: The Effect of Immersion in an Aqueous Fe(NO<sub>3</sub>)<sub>3</sub> Solutions

The article provides a comparative analysis of changes in the PL spectra and infrared spectroscopy (IR) with reference and immersion samples of mesoporous silicon during long-term storage in air at room temperature. Immersion was carried out in an aqueous solution of iron nitrate (Fe (NO3)3) with a concentration of 0.2 M and 0.5 M with three times: 5, 10 and 20 minutes. An analysis of the FIR data for etalon and immersion samples showed a number of features found during long-term storage of mesoporous silicon: (1) a sharp decrease in the density of hydride bonds; (2) the polynomial nature of the growth of O3-SiH and Si-OH bonds saturating dangling bonds; and (3) the polynomial growth of silicon dioxide with the formation of oxygen defects. It was found that after immersion in a solution of 0.5 M Fe (NO3)3 for 10 minutes, a more intense increase in the PL in mesoporous silicon is observed while maintaining its nanostructure after 200 days of storage compared with the etalon sample, for which a weak quantum size confinement (QSC) is observed. The main mechanism of photoluminescence increase in mesoporous silicon during long-term storage is radiative recombination from oxygen defect levels, not from a QSC effect.

Low Weight Hollow Microspheres of Iron with Thin Dielectric Coating: Synthesis and Microwave Permeability

Spray pyrolysis of an aqueous solution of iron nitrate, proceeded with reduction of the product in hydrogen, gave iron powder with micron-sized hollow particles. Coating these iron particles with SiO2 through tetraethyl orthosilicate hydrolysis prevented interparticle electrical contacts and suppressed DC percolation. This material shows a high ferromagnetic resonance frequency of 18 GHz, low permittivity, and weighs 20% less than common carbonyl iron. Potential microwave applications are for inductors and electromagnetic interference shielding designs.

Preparation, characterization, and application of nano‐FeOx/Al2O3/cordierite monolithic catalysts for heterogeneous dark Fenton reaction

AbstractBACKGROUNDAdvanced oxidation processes are an interesting alternative for wastewater treatment. The classic Fenton process, involving ferrous ions and hydrogen peroxide, requires strict pH adjustment and further iron removal. To overcome these difficulties, heterogeneous reaction with solid catalysts has been proposed. Until now, the solid catalysts have been employed as powders in agitated batch reactors. In this work, the application of structured catalysts for processes in flow is proposed. Nano‐FeOx/Al2O3/cordierite monolithic catalysts were prepared making firstly an alumina coating, and then impregnation with aqueous solution of iron nitrate at various concentrations. The synthesized catalysts were characterized using various techniques and then they were studied for the dark Fenton reaction.RESULTSThe coating adherence in the structured catalysts was better than 93%. Also, high homogeneity of the coating was confirmed. From results of physicochemical characterization, it was deduced that the active phase would consist of oligonuclear (FeO)n nanoclusters highly dispersed on the surface of the alumina support. The catalytic activity was evaluated in phenol peroxidation in aqueous phase (without light, pH 3, 30 °C), as a model reaction. The monolithic catalysts were active and chemically stable. The most active catalyst (phenol conversion > 90% at 80 min of reaction) was reused 12 times.CONCLUSIONSThe monolithic catalysts show a high potential for application in heterogeneous dark Fenton‐type reactions. Then, wastewater treatment by means of advanced oxidation processes could be carried out in continuous mode without further operation to separate the catalyst. © 2020 Society of Chemical Industry

Synthesis of Carbon Nanotubes from High-Density Polyethylene Waste

This article presents results of carbon nanotubes synthesis from household high-density polyethylene waste by thermal decomposition. A specific feature of this work is that the decomposition of high-density polyethylene waste and synthesis of carbon nanotubes were carried out in one-step using three-zone chemical vapor deposition reactor. The effect of temperature in the range of 450‒550 °C on decomposition products of high-density polyethylene was investigated. The decomposition products of polyethylene wastes were investigated by IR Fourier spectroscopy. Cenospheres obtained from ash and slag waste from thermal power plants during coal combustion were used as a catalyst for the synthesis of carbon nanotubes. The cenospheres were impregnated with an aqueous solution of iron nitrate. It was found that as a result of thermal decomposition of high-density polyethylene waste at temperature of 450 °C, gaseous carbon-containing compounds are formed, which upon further heating to 800 °C lead to the formation of carbon nanotubes with a diameter of 16‒21 nm on the surface of catalyst. Physicochemical analysis showed that turbostratic carbon is almost completely absent in the formed product. Carbon nanotubes analysis was performed by scanning electron microscopy and Raman spectroscopy.

Electron transport and magnetotransport in graphene films grown on iron thin film catalyst

Graphene films were grown by the low-pressure chemical vapor deposition with a single injection of acetylene on an iron film catalyst deposited on oxidized silicon substrate. After treatment of the graphene on the iron film with aqueous solution of iron nitrate the structures consisting of quasi-suspended graphene on reaction products of the iron film with iron nitrate were obtained. The electron transport and magnetotransport properties of the films were investigated. The films have a low resistance of 80 Ohm sq−1 and a high sheet carrier density (8 × 1013 cm−2 at room temperature). At temperatures less than 200 K, the dependence of the Hall resistance on the magnetic field is like the abnormal Hall effect. Large positive linear magnetoresistance at a room temperature (60–100%) was observed in the films in a field of 0.6 T, which is attractive for creating magnetoresistive sensors. It was found that the critical magnetic field at which the MR becomes linear is very small (116–650 Oe) and linearly dependent on a temperature. The MR is proportional to the average mobility 〈µ〉. At low temperatures, the magnetoresistance increases with increasing temperature. At higher temperatures the MR decreases with increasing temperature.

Large positive magnetoresistance of graphene at room temperature in magnetic fields up to 0.5 T

Graphene films were grown on an iron film catalyst deposited on oxidized silicon substrate, using the low-pressure chemical vapor deposition. Subsequently the iron film was dissolved with an aqueous solution of iron nitrate. The structures consisting of quasi-suspended graphene on reaction products of an iron film with iron nitrate were obtained. Magnetoresistance properties of the structures were investigated at a room temperature, and the positive magnetoresistance was observed. The maximum magnetoresistance value was 100% in the magnetic field of 0.5T. The dependence of magnetoresistance on the magnetic field was quasi-linear in the range of 0.07–0.5T.

Study on reduction behavior of two-component Fe[sbnd]Mg[sbnd]O oxide system prepared via a sol-gel technique

Two-component FeMgO oxide system was prepared via sol-gel technique. An aqueous solution of iron nitrate was used to hydrolyze the magnesium methoxide instead of distilled water. The iron loading in a final sample was 15 wt% with respect to Fe2O3. The method was shown to provide a uniform distribution of iron oxide within MgO matrix. The sample was characterized by means of a low-temperature nitrogen adsorption and scanning electron microscopy. Reduction behavior of the sample was studied in a temperature-programmed regime using hydrogen as a reducing agent. In order to follow the possible phase transformations, the sample was examined by an in situ X-ray diffraction analysis in both reductive and oxidative atmospheres within the temperature range of 25–700 °C. It was found that after the first cycle of reduction/re-oxidation, the sample stabilizes in a novel state, and hydrogen uptake profiles of further cycles of reductive/oxidative treatment become completely reproducible. According to X-ray diffraction data, the sample consists of small particles (9 nm) of Fe3O4 phase well-dispersed within the structure of nanocrystalline MgO.

Magnetic Rattle-Type Core–Shell Particles Containing Iron Compounds with Acid Tolerance by Dense Silica

Magnetic rattle-type particles, comprising magnetite or metallic iron in nonporous dense hollow silica microspheres, were fabricated by using sol–gel reactions of alkylsilyl trichlorides around droplets of aqueous iron nitrate solution in a water-in-oil emulsion. After evaporation of water within the silica capsules to leave iron salts, calcination of the dried sample was conducted to transform into a hematite (α-Fe2O3) core and porous hollow silica shell by losing alkyl groups of polyalkylsiloxane. Hydrogen gas penetrated through the silica shell and reduced hematite to magnetite (Fe3O4) at 310 °C and metallic iron (α-Fe) at 450 and 500 °C. The reduction at 310 °C resulted in largest magnetization at 12 kOe among the present magnetic particles. The core magnetic compounds were enclosed by a dense silica shell, which was transformed from porous silica by annealing in nitrogen at 700 °C. Because the magnetic particles were encapsulated by the dense silica shell, the magnetism was shown even after immersion...

Factors governing the efficiency of dissolution of UO2 ceramic pellets in aqueous solutions of iron nitrate

Dissolution of ceramic UO2 in aqueous Fe(NO3)3 solutions at different temperatures under the conditions of limited contact with air and in the autoclave mode was studied. In the course of UO2 dissolution at 60–90°C, the U/Fe molar ratio appears to be ∼1, whereas at room temperature (25°C) this value is ∼0.5. By varying the acidity of Fe nitrate solutions at these temperatures, it is possible to increase the U/Fe molar ratio to ∼4 and to obtain uranyl nitrate solutions with simultaneous removal of Fe from the solution in the form of a precipitate of the basic salt, or to perform quantitative dissolution of UO2 under the conditions excluding the formation of such precipitate. In the course of dissolution of ceramic UO2 in Fe(NO3)3 solutions, the appearance or absence of Fe(II) ions, the formation or absence of the precipitate of the Fe basic salt, and variation of solution pH are interrelated and are determined by the process temperature.

Iron impregnated SBA-15, a mild and efficient catalyst for the catalytic hydride transfer reduction of aromatic nitro compounds

Ordered hexagonal mesoporous Fe-SBA-15 with a large pore diameter was synthesized by a simple wet impregnation method using an aqueous solution of iron nitrate as a precursor. The incorporation of iron into the channels of mesoporous silica was confirmed and its textural and morphological properties were studied by various characterization techniques such as XRD, N2 adsorption–desorption isotherms, FTIR and DRS UV-vis spectroscopy, XPS and SEM. The catalytic activity of Fe-SBA-15 was studied for the catalytic hydride transfer reaction of aromatic nitro compounds into amino compounds. The regio-selectivity of the reduction of different nitro substituted compounds with Fe-SBA-15 was discussed.

Catalytic etching of synthetic diamond crystallites by iron

For the expansion of the functionality of diamond crystallites by modification of surface morphology, catalytic etching of synthetic diamond crystallites at 1173K by iron, which were loaded by the impregnation method using an aqueous solution of iron nitrate; in a streaming mixed gas (pH2=0.1 MPa, pN2=0.9 MPa), has been investigated by scanning electron microscopy (SEM) and Raman spectroscopy. The dependence of the crystal planes {111} and {100}, of the diamond crystallites and the loading amount of iron on the diamond on the etching behavior by iron particles, the morphology of the etch pits, and potential formation of iron carbide through the catalytic etching, were discussed.

Catalytic Oxidation of Toluene over Fe<sub>2</sub>O<sub>3</sub>/Al<sub>2</sub>O<sub>3</sub> Catalyst

Fe2O3/Al2O3 catalyst was prepared and the catalytic oxidation of toluene over the catalyst was investigated. The catalyst was prepared by wet impregnation of commercial alumina support. The support was impregnated with an aqueous solution of iron nitrate. The wet support was dried and calcined at 600-800 °C. The catalytic property of the catalyst was measured by the light-off curve of CO2 yield. All these catalysts were active for total oxidation of toluene above 250 °C. The catalytic activity of catalyst calcined at 600 °C was better than those of catalysts calcined at 700 and 800 °C.

Bottom-up in situ formation of Fe3O4 nanocrystals in a porous carbon foam for lithium-ion battery anodes

A facile and scalable process for the in situ formation of Fe3O4 nanocrystals in a pre-formed carbon foam (CF) (Fe3O4/CF) was developed, which involved impregnation of an aqueous iron nitrate solution onto CF followed by controlled thermal treatment in an inert atmosphere. N2adsorption/desorption and BET measurements showed that the CF was a mesoporous carbon with a high pore volume and specific surface area. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction measurement, thermogravimetric analysis, and X-ray photoelectron spectroscopy (XPS) revealed that 5–50 nm Fe3O4 nanocrystals at a high loading of 78.7 wt% were formed preferentially in the confined pores of CF. When tested for anode material in a Li ion half-cell, the Fe3O4/CF composite was far superior to unsupported Fe3O4 nanocrystals, exhibiting significantly improved Coulombic efficiencies and cycling stability and achieving >780 mA h g−1 after 50 deep charge–discharge cycles with >95% cycling efficiency.

Synthesis of SiFeC Magnetoceramics from Reverse Polycarbosilane‐Based Microemulsions

In this paper, we report the synthesis of iron‐containing SiC(O) magnetoceramics using a reverse microemulsion technique. First, an aqueous iron nitrate solution as the internal phase and a polycarbosilane (PCS)–heptane solution as the continuous phase were emulsified in the presence of a surfactant to synthesize iron‐containing PCS (Fe‐PCS) reverse microemulsion systems. After the removal of water and heptanes, the Fe‐PCS precursors were pyrolyzed at 600°–1200°C to produce magnetoceramics. The structures and magnetic properties of the ceramics obtained were characterized by using X‐ray diffraction, transmission electron microscopy, electron probe microanalysis, and superconducting quantum interference device. The results showed that the ceramics contained Fe3Si nanoparticles, which dispersed in SiCO amorphous matrix. This unique structure makes the ceramics excellent soft ferromagnetic materials with a high magnetizability and negligibe hysteresis loops.

Impedance Response of Franklinite Films to Humidity and Propane

Iron-Zinc oxide films were deposited by the well known ultrasonic spray pyrolysis method from an aqueous solution of iron nitrate and zinc acetate ([Zn]/[Fe] = 0.30). A Franklinite structure of these films turned out from XRD measurements. Additional basic characterization with UV-Vis and infrared spectroscopies and AFM was also performed. Electrical measurements under a small alternating current signal (15 mV RMS) were performed under dry air, humid air (53 % R:H.) and humid air plus propane. Frequency scans yielded sensitivities as high as 260% to humidity and  475% to propane at 30 °C. At 250 °C lower sensitivities were obtained, but in all cases the highest values came from the reactive response of the film. From dynamical response measurements, the response time was also assessed. The mechanisms of sensing are discussed as well.

Opal-Hematite and Opal-Magnetite Films: Lateral Infiltration, Thermodynamically Driven Synthesis, Photonic Crystal Properties

Hematite (α-Fe2O3) was infiltrated into opal film pores without depositing the oxide onto the outer film surface by the developed method of lateral infiltration of an aqueous solution of iron nitrate under capillary forces. The thermodynamically driven syntheses of either Fe3O4 (magnetite) or α-Fe were performed in the opal pores using α-Fe2O3 as a precursor. The opal-α-Fe2O3 and opal-Fe3O4 films were characterized by scanning electron microscopy, X-ray diffraction, reflectance, and transmittance measurements. The photonic band gap red-shifted gradually as the number of lateral infiltration runs increased. The maximum filling degrees both of opal-α-Fe2O3 and of opal-Fe3O4 films, calculated from the reflection spectra, appeared to be similar and equal to ∼55% of the pore volume because of very close values of molar volumes of the oxides. It was found that the reversible chemical transformation of fillers in opal pores α-Fe2O3 ↔ Fe3O4 ↔ α-Fe2O3 changes only the filler dielectric constant but does not practi...

Critical evaluation of the state of iron oxide nanoparticles on different mesoporous silicas prepared by an impregnation method

Mesoporous SBA-15 (space group p6 mm), KIT-6 ( Ia3 d) and KIT-5 ( Fm3 m) silicas, exhibiting different 2-D and 3-D channel- or cage-like pore structure and pore dimensions have been used as supports for iron oxide nanoparticles. The iron modification of the silica was performed according to a frequently used impregnation technique from aqueous iron nitrate solution. The materials were characterized by nitrogen physisorption, X-ray diffraction, TEM–EDX, Moessbauer spectroscopy, and temperature-programmed reduction (TPR) and tested in the catalytic decomposition of methanol. It is established that the location and dispersion of iron oxide nanoparticles are affected by the pore topology of the support. The most homogeneously dispersed iron oxide nanoparticles are observed using silica host matrix exhibiting a 3-D channel-like structure and pore diameters about 7 nm, and the thus-obtained composites exhibit high catalytic activity and selectivity in methanol decomposition to CO and hydrogen. For all the samples, characterized with a low mesopore volume and small pore diameters/pore entrances, the formation of larger iron oxide particles, mainly located on the outer surface, is observed. Inhomogeneously dispersed iron oxide particles with a large fraction of isolated, strongly interacting with the support, iron species, and possessing low catalytic activity and usually high selectivity to methane, are found for the silicas with relatively larger pores/pore entrances.

Synthesis of very dense carbon nanotube bundles using silica supported metal catalyst

We prepared iron-impregnated silica films, which turned out to be very efficient catalysts for carbon nanotube synthesis, by a sol-gel process starting from the mixture of tetraethyl orthosilicate (TEOS), aqueous solution of iron nitrate (Fe(NO3)3⋅9H2O), and ethanol. The Fe/silicate-composite catalyst films consisted of nanoparticles, the composition and diameter of which depended on the iron-nitrate molarity in aqueous solution. Within the range of 0.5–1.5 M, the nanocomposite particles maintained good catalytic capacity, and very long and dense bundles of multiwall carbon nanotubes were synthesized regardless of the iron-nitrate molarity. The carbon nanotube density was so high that the nanotube bundles appeared made of aligned nanotubes in spite of the curliness of the individual nanotubes. However, carbon nanotubes were scarcely synthesized below 0.4 M of iron-nitrate molarity, which we attributed to the unfavorable composition and distribution of Fe-species in nanocomposite particles.