Ultrafine Iron Oxide Research Articles

Remarkable efficiency of ultrafine superparamagnetic iron(III) oxide nanoparticles toward arsenate removal from aqueous environment

Arsenates, when present in water resources, constitute a risk to human health. In order to remove them, various technologies have been developed; out of them, sorption approach is widely adopted employing a wide spectrum of suitable sorbent materials. Nanoparticles of iron oxide are frequently used due to a high surface area and ability to control them by external magnetic field. In this work, we report on a simple and cheap synthesis of ultrafine iron(III) oxide nanoparticles with a narrow size distribution and their exploitation in the field of arsenate removal from aqueous environment. It is shown that the adsorption capacity is enhanced by a mesoporous nature of nanoparticle arrangement in their system due to strong magnetic interactions they evolve between nanoparticles. A complete arsenate removal is achieved at Fe/As ratio equal to ∼20/1 and at pH in the range from 5 to 7.6. Under these conditions, the arsenates are completely removed within several minutes of treatment. Among iron-oxide-based nanosystems synthesized and employed in arsenate remediation issues so far, our assembly of iron(III) oxide nanoparticles shows the highest Freundlich adsorption coefficient and equilibrium sorption capacity under conditions maintained. Taking into account simple and low-cost preparation procedure, product high yields, almost monodispersed character, room-temperature superparamagnetic behavior, and strong magnetic response under small applied magnetic fields, the synthesized iron(III) oxide nanoparticles can be regarded as a promising candidate for exploitation in the field of removing undesired toxic pollutants from various real water systems.

LIGHT SCATTERING BEHAVIOR OF MAGNETIC FIELD INDUCED DIRECTIONAL SELF ASSEMBLY OF IRON OXIDE NANOPARTICLE SUSPENSION

The magnetic control on scattering of light by ultrafine iron oxide (γ- Fe2O3 ) nanoparticles suspended in a carrier liquid was investigated. The light scattering behavior was studied using laser light under the influence of a permanent magnet over a rotating frame of reference. When the magnet is rotated continuously from 0° to 360° with respect to the direction of the incident laser beam, the scattered light pattern from the sample has the same angular displacement but in counter direction to the magnetic field rotation. When external field is not applied to the ferrofluid, no other preferred directional scattering of light is observed. The applied magnetic field induces directional self assembly of magnetic nanoparticles through dipole–dipole interactions. This finally leads to the formation of "nanoparticle grating" and the optical geometry of diffraction grating clearly describes the anomalous scattering behavior of the ferrofluid. Most interestingly, for each complete orientation of the field from 0° to 360°, the transmitted light intensity switches between maxima and minima for longitudinal and transverse applied magnetic fields.

Facile method to synthesize magnetic iron oxides/TiO2 hybrid nanoparticles and their photodegradation application of methylene blue

Many methods have been reported to improving the photocatalytic efficiency of organic pollutant and their reliable applications. In this work, we propose a facile pathway to prepare three different types of magnetic iron oxides/TiO2 hybrid nanoparticles (NPs) by seed-mediated method. The hybrid NPs are composed of spindle, hollow, and ultrafine iron oxide NPs as seeds and 3-aminopropyltriethyloxysilane as linker between the magnetic cores and TiO2 layers, respectively. The composite structure and the presence of the iron oxide and titania phase have been confirmed by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectra. The hybrid NPs show good magnetic response, which can get together under an external applied magnetic field and hence they should become promising magnetic recovery catalysts (MRCs). Photocatalytic ability examination of the magnetic hybrid NPs was carried out in methylene blue (MB) solutions illuminated under Hg light in a photochemical reactor. About 50% to 60% of MB was decomposed in 90 min in the presence of magnetic hybrid NPs. The synthesized magnetic hybrid NPs display high photocatalytic efficiency and will find recoverable potential applications in cleaning polluted water with the help of magnetic separation.

ARSENIC REMEDIATION USING SURFACE FUNCTIONALIZED ULTRAFINE NANOPARTICLES

Ultrafine nanoparticles owing to their increased surface to volume ratio, coupled with the ability to tune their surface properties through molecular modification have made them ideal for their detection and remediation of broad range of environmental contaminants. Arsenic contamination has become a worldwide epidemic and remediation of this problem needs the development of technology with improved materials and systems with high efficiency. In the present study, we have demonstrated a simple and efficient method using surface functionalized ultrafine iron oxide nanoparticles for absolute removal of arsenic from arsenic treated water with low contact time period and low adsorbent dose. The efficiency of arsenic removal has been drastically improved by considering nanoparticles of size 10 nm and subsequent surface engineering of the nanoparticles resulting more adsorption sites being exposed to arsenic. The mechanism for adsorption was identified through electron microscopic and spectroscopic studies. The adsorption equilibrium data were well fitted to Freundlich isotherm.

Arsenic (III,V) removal from aqueous solution by ultrafine α-Fe 2O 3 nanoparticles synthesized from solvent thermal method

Ultrafine iron oxide (α-Fe 2O 3) nanoparticles were synthesized by a solvent thermal process and used to remove arsenic ions from both lab-prepared and natural water samples. The α-Fe 2O 3 nanoparticles assumed a near-sphere shape with an average size of about 5 nm. They aggregated into a highly porous structure with a high specific surface area of ∼162 m 2/g, while their surface was covered by high-affinity hydroxyl groups. The arsenic adsorption experiment results demonstrated that they were effective, especially at low equilibrium arsenic concentrations, in removing both As(III) and As(V) from lab-prepared and natural water samples. Near the neutral pH, the adsorption capacities of the α-Fe 2O 3 nanoparticles on As(III) and As(V) from lab-prepared samples were found to be no less than 95 mg/g and 47 mg/g, respectively. In the presence of most competing ions, these α-Fe 2O 3 nanoparticles maintained their arsenic adsorption capacity even at very high competing anion concentrations. Without the pre-oxidation and/or the pH adjustment, these α-Fe 2O 3 nanoparticles effectively removed both As(III) and As(V) from a contaminated natural lake water sample to meet the USEPA drinking water standard for arsenic.

Investigation into the role of the boudouard reaction in self-reducing iron oxide and carbon briquettes

With increasing impetus to utilize more waste byproducts from ironmaking processes, a greater understanding of processes that utilize these wastes is required. In this article, the kinetics of reaction of briquettes consisting of ultrafine iron oxide and carbon are examined representing a progression in the understanding of methods to utilize fine iron oxide and carbon resulting from all stages of processing. More specifically, this article examines the role of the Boudouard reaction and its level of control in such reaction systems for the temperature range of 1000 °C to 1200 °C. Various techniques were used to examine this role, including investigating the effect of the surface area of the carbon used, the effect of a known Boudouard reaction catalyst, and the effect of temperature.

Programmable Self-Aligning Ferrofluid Masks for Lithographic Applications

A novel self-aligned soft method that is compatible with traditional photolithographic processes is demonstrated. This method uses a suspension of ultra-fine iron oxide grains (ferrofluid) to protect or de-protect selected areas of a magnetically patterned substrate according to a programmable sequence. Automatic mask formation and registration is controlled by ferromagnetic alignment marks patterned on a substrate. External magnetic fields applied to the system causes ferrofluid to aggregate only over designated areas on the surface, thereby masking those areas from UV and/or chemical exposure.

Synthesis of Ultra-Fine Iron-Oxide Nano-Particles in a Diffusion Flame with Electro-Spraying Assistance

Ultra-fine Fe2O3 nano-particles are synthesized using H2/O2 co-axial diffusion flame with the state-of-the-art electro-spraying (e-spray) technique at atmospheric condition. Fe(CO)5 is used as a precursor and the liquid phase Fe(CO)5 is injected directly into the center of the flame using the electro-spraying method. The synthesized particle morphology sampled from the inside of flame is analyzed by TEM. The synthesized particles showed different crystal structures for different particle collection method and the collection positions.

Fe3O4 Ultrafine Particles with Narrow Size Distribution from Polymer-Metal Complex Gels

ABSTRACTAlthough studies on the Fe3O4 magnetic particle formation have been markedly advanced by the strenuous efforts of numerous researchers, the preparation and formation of ultrafine Fe3O4 particles with narrow size distribution still remain as an open area due to their broad applications, especially in biomedical fields such as target drug delivery and medical imaging. A new method for the titled template-mediated synthesis of Fe3O4 ultrafine magnetite particles (several tens of nanometers) with narrow size distribution from a polymer matrix has been investigated. Hydrazine hydrate was used as a reducing agent to prepare the poly(itaconic acid-co-acrylic acid) gel-supported iron metallic nanoclusters, which served as nuclei, and were later transferred into ultrafine iron oxide powders in NaOH base solution. The morphology, particle size, structure and magnetic properties, as well as the formation of the particles with narrow size distribution, were investigated by means of transmission electron microscopy, selected area electron diffraction, laser light scattering, wide-angle X-ray diffraction, Fourier-transform infrared spectroscopy, and electron spectroscopy for chemical analysis, as well as magnetic measurements, respectively. It was revealed that the Fe3O4 ultrafine particles prepared from the Fe3+-poly(itaconic acid-co-acrylic acid) complex gel system kept narrow size distribution, which originated from the oxidation and aggregation growth of the primary particles, and the metallic iron nanoclusters would act as “templates” in the later magnetite particles growth stage. This new attempt of template-mineralization of Fe3O4 ultrafine particles in our preparation was proved to be effective for preparing template-mediated ultrafine magnetite particles with narrow size distribution quickly, which could also be used to prepare other kinds of inorganic particles.

Characterization of ultrafine zirconia and iron oxide powders prepared under hydrothermal conditions

Nanocrystalline zirconia (6-20 nm) and iron oxide (20-80 nm) powders were produced by hydrothermal treatment of corresponding hydroxides and nitrate solutions. The synthesis parameters (temperature, duration, concentration) allow fabrication of ultrafine oxide powders with various particle size and morphology. The smallest particles were produced by short-time (4-7 s) treatment of nitrate solutions (PH ≈ 1). Prepared nanocrystalline powders exhibit high activity in model solid state reactions.

96/03628 Fischer-Tropsch synthesis: impact of potassium and zirconium promoters on the activity and structure of an ultrafine iron oxide catalyst

96/03628 Fischer-Tropsch synthesis: impact of potassium and zirconium promoters on the activity and structure of an ultrafine iron oxide catalyst

Fischer-Tropsch synthesis: Impact of potassium and zirconium promoters on the activity and structure of an ultrafine iron oxide catalyst

Slurry phase Fischer-Tropsch synthesis was conducted with an ultrafine iron oxide catalyst promoted with either 0.5 at% K or 1.0 at% Zr or both. Pretreatment in CO yielded higher conversions and a more stable catalyst than activation in hydrogen or synthesis gas. Hydrogen pretreatment of K promoted catalysts and synthesis gas activation in general were less effective. Mossbauer spectroscopy and XRD showedχ-Fe5C2 and e′-Fe2.2C were formed during pretreatment in CO and did not depend on promoters present. Catalysts pretreated in H2 were reduced to metallic Fe and Fe3O4; promotion with K and Zr decreased the extent of reduction. Hydrogen pretreated catalysts, promoted with K, lost surface area and carbided rapidly under synthesis conditions. Activation in synthesis gas reduced all catalysts to Fe3O4. Subsequent synthesis did not affect the phase present for the unpromoted and Zr promoted catalysts while those promoted with K formed χ-Fe5C2 and e′-Fe2.2C. It is concluded that pretreatment type is more important to the catalyst activity during the early period of synthesis than the impact of promotion with K and/or Zr and that changes in the bulk composition of iron catalysts do not necessarily correlate with changes in activity.

32.O.06 Measurement of the properties of ultrafine iron oxide particles by means of on-line detection of particle magnetization, TDMA and STEM-analysis

32.O.06 Measurement of the properties of ultrafine iron oxide particles by means of on-line detection of particle magnetization, TDMA and STEM-analysis

Evaluation of the effect of a nonporous ultrafine iron catalyst on the hydroliquefaction of a highly volatile bituminous coal

The effect ofa nonporous ultrafine iron oxide precursor, prepared by a flame method, was evaluated in the hydroliquefaction of a bituminous coal in tetralin (350, 400, 430 °C) on a laboratory scale, and compared to that of other aerosols (silica, alumina, SnO 2 , MoO 3 , NiMo/Al 2 O 3 ). The precursors were sulfided with S during heating, according to a previously established conditions set. Methods of evaluating catalytic activity in hydroliquefaction runs based on extraction yields are strongly dependent on the experimental conditions. Special emphasis has been given here in the application of two alternative parameters bred on electron spin resonance (ESR) data, and on the ratio of hydrogen consumption from the gas to that from the solvent (H gas /H solv )

IRON FISCHER-TROPSCH CATALYSIS — PROPERTIES OF AN ULTRAFINE IRON OXIDE CATALYST

ABSTRACT ABSTRACT Slurry phase Fischer-Tropsch synthesis has been conducted starting with an ultrafine iron oxide catalyst with an average particle size of 30A. Catalyst activity gradually increased during the first 400 hour of synthesis and then remained stable for 250 days. Potassium promotion greatly increased the initial activity of the catalyst; however, the stability decreased. The CO conversion of the unpromoted catalyst was found to vary linearly with the reciprocal of the space velocity up to 60% conversion. Alkene selectivity increased with increasing space velocity but remained constant above GHSV = 2,0. Secondary reactions are believed to account for the higher alkane content at low space velocity. Methane, ethane and alkane formation increased with increasing hydrogen partial pressure up to a H2/CO ratio of 1. CO conversion is highest at lowest CO partial pressure and likewise for hydrogen. In general it is observed that this ultrafine catalyst is not as active as precipitated catalysts and h...

Particle interaction effects in systems of ultrafine iron oxide particles

By means of Mössbauer spectroscopy and magnetic susceptibility measurements we have studied the superparamagnetic relaxation of ultrafine maghemite particles. The behaviour of oleic acid coated and uncoated particles is compared. The effects of pressing the samples are also investigated. The observed differences are ascribed to the difference in the strength of the magnetic interaction between the particles in the samples.

Ultrafine iron oxide powders generated using a flow-through hydrothermal process

The rapid thermal decomposition of precursors in solution (RTDS) method is introduced as a mechanism for generating ultrafine iron oxide powders. Particle size and crystallinity characteristics are related to the RTDS processing conditions and to the salt used as the iron oxide precursor.

M�ssbauer spectroscopic characterization of ultrafine iron oxide and oxyhydroxide prepared by oxidative hydrolysis

The formation of small iron oxyhydroxide particles in the course of oxidative hydrolysis of Fe(II) sulphate has been investigated by Mossbauer spectroscopy. The influence of the basic temperature as basic parameter on the properties of the iron oxyhydroxide produced has been established. The results obtained are explained by a scheme of a process, including chemical and physical stages.

Ordered aggregates of ultrafine iron oxide particles: ‘Super crystals’

Abstract Ultrafine iron oxide particles with a mean diameter of 6.9 nm and a very narrow size distribution have been studied by electron microscopy, Mössbauer spectroscopy, and X-ray diffraction. Electron micrographs and electron diffraction patterns show that the particles form ‘super crystals’, that is, three-dimensional ordered close-packed structures, with a nearest neighbour distance of 9.1 nm.

マイクロ波プラズマCVD法による超微粒子状鉄酸化物の合成

マイクロ波プラズマCVD法による超微粒子状鉄酸化物の合成