Showing papers on "Magnetite published in 2020"
TL;DR: The literature collection and discussion on the critical assessment of reserving the environmental sustainability challenges provided in this review will be useful not only for experienced researchers but also for novices in the field.
Abstract: The optoelectrical and magnetic characteristics of naturally existing iron-based nanostructures, especially hematite and magnetite nanoparticles (H-NPs and M-NPs), gained significant research inter...
90 citations
TL;DR: Magnetic magnetite nanoparticles (MMN) was used as an adsorbent for effective boron removal and isotopic separation in aqueous solution for the first time as discussed by the authors.
69 citations
TL;DR: Both Fe3 O4 and silica-coated Fe3O4 NPs demonstrated better antimicrobial activities and were tested against Gram-negative and Gram-positive bacteria.
Abstract: Magnetite and silica-coated magnetite (Fe3O4) nanoparticles (NPs) were synthesized by water-in-oil (W/O) microemulsion method from hydrated ferric nitrate, ferrous sulfate precursors and ammonia a precipitating agent with the assistance of Tween-80 and SDS surfactants. The synthesized materials were characterized by X-ray diffraction, scanning electron microscopy, thermal analyzer, and infrared spectroscopy. X-ray diffraction pattern of Fe3O4 showed that particles were phase pure with a cubic inverse spinel structure and FT-infrared spectra confirmed the presence of Fe-O bond in tetrahedral and octahedral interstitial sites. The crystallite size determined from powder XRD data with Scherer’s equation was in the range of 7.3 ± 0.05 nm–10.83 ± 0.02 nm for uncoated Fe3O4 and 16 ± 0.14 nm for silica-coated Fe3O4 NPs. The SEM micrographs of the uncoated Fe3O4 oxide revealed the agglomeration of the magnetite (Fe3O4) particles. But the silica-coated Fe3O4 oxide exhibited homogeneous distribution of particles with relatively less agglomerate of the particles. The particle size of Fe3O4 NPs slightly increased with the temperature and precursor concentration. The antimicrobial activities of Fe3O4 and silica-coated Fe3O4 nanoparticles were tested against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Bacillus subtilis) bacteria. Both Fe3O4 and silica-coated Fe3O4 NPs demonstrated better antimicrobial activities.
68 citations
TL;DR: This study demonstrates that SMR is a promising technology for the recovery of iron from red mud by demonstrating that both magnetite and maghemite were found in the roasted product.
65 citations
TL;DR: In this article, the removal efficiencies of p-nitrophenol (PNP) by micro zero-valent iron (mFe0) could maintain at the satisfactory level in the process of continuous reactions (20 cycles).
61 citations
TL;DR: In-situ precipitation method is widely used and reported in the literature for the synthesis of iron oxide nanoparticles based on their applications in many fields as discussed by the authors, however, the rate of reaction an...
Abstract: In-situ precipitation method is widely used and reported in the literature for the synthesis of iron oxide nanoparticles based on their applications in many fields. However, the rate of reaction an...
59 citations
19 Mar 2020
TL;DR: In this paper, the authors take a closer look at the synthesis of magnetic iron oxide nanoparticles through the co-precipitation of iron salts in an alkaline environment, and the correlation between the particle properties and the various parameters of the synthesis was modelled with linear mixture models.
Abstract: Today, magnetic nanoparticles are present in multiple medical and industrial applications. We take a closer look at the synthesis of magnetic iron oxide nanoparticles through the co-precipitation of iron salts in an alkaline environment. The variation of the synthesis parameters (ion concentration, temperature, stirring rate, reaction time and dosing rate) change the structure and diameter of the nanoparticles. Magnetic iron oxide nanoparticles are characterized by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM). Magnetic nanoparticles ranging from 5 to 16 nm in diameter were synthesized and their chemical structure was identified. Due to the evaluation of Raman spectra, TEM and XRD, the magnetite and maghemite nanoparticles can be observed and the proportion of phases and the particle size can be related to the synthesis conditions. We want to highlight the use of Raman active modes A1g of spinel structured iron oxides to determine the content of magnetite and maghemite in our samples. Magnetite nanoparticles can be derived from highly alkaline conditions even without establishing an inert atmosphere during the synthesis. The correlation between the particle properties and the various parameters of the synthesis was modelled with linear mixture models. The two models can predict the particle size and the oxidation state of the synthesized nanoparticles, respectively. The modeling of synthesis parameters not only helps to improve synthesis conditions for iron oxide nanoparticles but to understand crystallization of nanomaterials.
58 citations
TL;DR: It is found that U reduction can occur on the surface of magnetite via transient U nanowire structures which collapse into ordered UO2 nanoclusters, which may have implications for understanding nuclear waste evolution and remediation of uranium contamination.
Abstract: Uranium (U) is a ubiquitous element in the Earth’s crust at ~2 ppm. In anoxic environments, soluble hexavalent uranium (U(VI)) is reduced and immobilized. The underlying reduction mechanism is unknown but likely of critical importance to explain the geochemical behavior of U. Here, we tackle the mechanism of reduction of U(VI) by the mixed-valence iron oxide, magnetite. Through high-end spectroscopic and microscopic tools, we demonstrate that the reduction proceeds first through surface-associated U(VI) to form pentavalent U, U(V). U(V) persists on the surface of magnetite and is further reduced to tetravalent UO2 as nanocrystals (~1–2 nm) with random orientations inside nanowires. Through nanoparticle re-orientation and coalescence, the nanowires collapse into ordered UO2 nanoclusters. This work provides evidence for a transient U nanowire structure that may have implications for uranium isotope fractionation as well as for the molecular-scale understanding of nuclear waste temporal evolution and the reductive remediation of uranium contamination. In anoxic environments, soluble hexavalent uranium is reduced and immobilized, however, the underlying molecular-scale reduction mechanism remains unknown. Here, the authors find that U reduction can occur on the surface of magnetite via transient U nanowire structures which collapse into ordered UO2 nanoclusters, which may have implications for understanding nuclear waste evolution and remediation of uranium contamination.
57 citations
03 Jun 2020
TL;DR: In this paper, a synthesis of recent studies focused on the corrosion product layers forming on carbon steel in natural seawater and the link between the composition of these layers and the corrosion mechanisms is presented.
Abstract: This article presents a synthesis of recent studies focused on the corrosion product layers forming on carbon steel in natural seawater and the link between the composition of these layers and the corrosion mechanisms. Additional new experimental results are also presented to enlighten some important points. First, the composition and stratification of the layers produced by uniform corrosion are described. A focus is made on the mechanism of formation of the sulfate green rust because this compound is the first solid phase to precipitate from the dissolved species produced by the corrosion of the steel surface. Secondly, localized corrosion processes are discussed. In any case, they involve galvanic couplings between anodic and cathodic zones of the metal surface and are often associated with heterogeneous corrosion product layers. The variations of the composition of these layers with the anodic/cathodic character of the underlying metal surface, and in particular the changes in magnetite content, are thoroughly described and analyzed to enlighten the self-sustaining ability of the process. Finally, corrosion product layers formed on permanently immersed steel surfaces were exposed to air. Their drying and oxidation induced the formation of akaganeite, a common product of marine atmospheric corrosion that was, however, not detected on the steel surface after the permanent immersion period.
57 citations
TL;DR: In this article, the authors reported a facile and green biosynthetic co-precipitation of magnetite nanoparticles using extract from the root of Chromolaena odorata.
56 citations
TL;DR: In this article, the effects of suspension magnetization roasting (SMR) operation parameters on its ability to extract iron from red mud were investigated, and the results indicate that hematite and goethite phases present in the raw red mud are transformed into magnetite and maghemite during the SMR process.
TL;DR: In this article, magnetite nanoparticles were used as electron carriers to enhance extracellular electron transfer in single chamber MESs, and the MES with magnetite exhibited the highest methane yield and current generation.
TL;DR: The above study indicates that control size, shape, and interparticle interactions is required to strictly discuss such delicate differences of magnetic anisotropy of individual magnetite nanoparticles for the design of thermal seeds for magnetic hyperthermia.
Abstract: Ideal interaction-free magnetite nanoparticles were prepared, and their magnetic properties were measured to clarify the true nature of magnetic anisotropy of individual magnetite nanoparticles at
TL;DR: In the new model reactors, inhibition of methanogenesis by magnetite was avoided compared with that of the magnetite-only reactors, and hydrolysis efficiency was improved via dissimilatory iron reduction compared with those of ZVI- only reactors.
TL;DR: In this paper, the authors used the advantages of porous covalent organic frameworks by preparing them in a usable magnetite support form with Fe3O4 nanoparticles using the solvothermal methane.
Abstract: The present study focused on utilizing the advantages of porous covalent organic frameworks by preparing them in a usable magnetite support form with Fe3O4 nanoparticles using the solvothermal meth...
TL;DR: The here presented non-toxic magnetic nanoparticle system enables the tuning of the magnetic properties of the particles without a remarkable change in particles size and the found heating performance is suitable for magnetic hyperthermia application.
Abstract: Magnetite (Fe3O4) particles with a diameter around 10 nm have a very low coercivity (Hc) and relative remnant magnetization (Mr/Ms), which is unfavorable for magnetic fluid hyperthermia. In contrast, cobalt ferrite (CoFe2O4) particles of the same size have a very high Hc and Mr/Ms, which is magnetically too hard to obtain suitable specific heating power (SHP) in hyperthermia. For the optimization of the magnetic properties, the Fe2+ ions of magnetite were substituted by Co2+ step by step, which results in a Co doped iron oxide inverse spinel with an adjustable Fe2+ substitution degree in the full range of pure iron oxide up to pure cobalt ferrite. The obtained magnetic nanoparticles were characterized regarding their structural and magnetic properties as well as their cell toxicity. The pure iron oxide particles showed an average size of 8 nm, which increased up to 12 nm for the cobalt ferrite. For ferrofluids containing the prepared particles, only a limited dependence of Hc and Mr/Ms on the Co content in the particles was found, which confirms a stable dispersion of the particles within the ferrofluid. For dry particles, a strong correlation between the Co content and the resulting Hc and Mr/Ms was detected. For small substitution degrees, only a slight increase in Hc was found for the increasing Co content, whereas for a substitution of more than 10% of the Fe atoms by Co, a strong linear increase in Hc and Mr/Ms was obtained. Mossbauer spectroscopy revealed predominantly Fe3+ in all samples, while also verifying an ordered magnetic structure with a low to moderate surface spin canting. Relative spectral areas of Mossbauer subspectra indicated a mainly random distribution of Co2+ ions rather than the more pronounced octahedral site-preference of bulk CoFe2O4. Cell vitality studies confirmed no increased toxicity of the Co-doped iron oxide nanoparticles compared to the pure iron oxide ones. Magnetic heating performance was confirmed to be a function of coercivity as well. The here presented non-toxic magnetic nanoparticle system enables the tuning of the magnetic properties of the particles without a remarkable change in particles size. The found heating performance is suitable for magnetic hyperthermia application.
TL;DR: The results show that mechanically removing the surface layers that accumulate on electrodes over extended periods of Fe-EC operation can restore Fe- EC system efficiency (concentration of solute removed/kWh delivered), and suggest that routine electrode maintenance can ensure robust and reliableFe-EC performance over year-long timescales.
TL;DR: Copper-modified magnetite showed higher catalytic activity for H2O2 conversion to HO• (estimated using 7-hydroxycoumarin), compared to pristine magnetite (Fe3O4), and improved degradation of the anticancer drugs 5-fluorouracil and cyclophosphamide was observed.
TL;DR: In this article, the pre-concentration followed by magnetization roasting and magnetic separation process was well recognized as one of the most important secondary mineral resources in the world.
Abstract: Iron ore tailing is currently one of the most important secondary mineral resources. Pre-concentration followed by magnetization roasting and magnetic separation process was well recognized...
TL;DR: The increasing silica content increased the drug loading owing to the increasing number of OH− bonds in silica, resulting in strong bonds with doxorubicin, and the magnetite/silica nanocomposites could be applied as drug delivery vehicles.
TL;DR: The spin resonance properties obtained from fitting the FMR data clearly indicate that a large spin-orbit coupling was observed for the single phase Fe3O4 MNPs and excellent magnetic properties were obtained from the static magnetic measurements.
Abstract: Herein, we have presented a detailed investigation of the temperature effect on hydrothermal synthesis of Fe3O4 magnetic nanoparticles (MNPs). The appearance of single-phase cubic spinel Fe3O4 at and above critical temperature provides a clear indication that temperature plays a crucial role in the single-phase synthesis of the Fe3O4 MNPs. A detailed investigation of the structural, magnetic and spin dynamic properties of PEG-400 coated Fe3O4 MNPs synthesized by a facile hydrothermal method at different temperatures (120 °C, 140 °C, 160 °C and 180 °C for 16 hours) has been presented. The single-phase cubic magnetite structure with high crystallinity was found in the samples synthesized at 160 and 180 °C and confirmed from XRD results, whereas samples prepared at 120 and 140 °C are of mixed phase (α-Fe2O3 and Fe3O4). The magnetic hysteresis curves reveal that saturation magnetization and coercivity of MNPs enhanced systematically with the increase in the reaction temperature from 120 °C to 180 °C. Maximum saturation magnetization (88.98 emu g−1) and coercivity (134.16 Oe) were found for the sample synthesized at 180 °C. Furthermore, ferromagnetic resonance (FMR) spectra obtained for samples synthesised at higher temperatures indicate a lower value of the line width due to the high magnetic ordering in the samples. Also, the resonance field decreased, and the g-value increased due to enhancement in magnetization for the single-phase samples synthesized at higher reaction temperatures. The spin resonance properties obtained from fitting the FMR data clearly indicate that a large spin–orbit coupling was observed for the single phase Fe3O4 MNPs and excellent magnetic properties were obtained from the static magnetic measurements.
TL;DR: In this paper, two different sizes and surface characteristics of two different magnetite particles were chosen as the sorbents to examine their adsorption and desorption behavior toward phosphate.
Abstract: Eutrophication caused by excessive phosphate discharge into surface water has raised wide concern, and the efficient removal of phosphates from wastewater using sorption methods is very important. In our study, magnetite particles with two different sizes and different surface characteristics were chosen as the sorbents to examine their adsorption and desorption behavior toward phosphate. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption–desorption methods were used to characterize the morphological and surface chemical properties of the two differently sized magnetite particles. Adsorption kinetics and isotherm models (including the pseudo-first-order, Freundlich, Langmuir and Temkin models) were used to fit the experimental data, and to help with the mechanistic discussions. It was found that the nanometer-sized magnetite (nFe3O4) has a much higher surface area, larger pore volume, higher amounts of surface functional groups, and a lower point of zero charge (pHPZC) value than the micrometer-sized magnetite (Fe3O4). The adsorption kinetics show that reaching adsorption equilibrium in the case of nFe3O4 is much slower, and the particle size or surface characteristics of the magnetite may become the main factor determining the adsorption rate of the phosphate to magnetite in the rapid or slow adsorption step, respectively. nFe3O4 shows much stronger adsorption of phosphate compared to Fe3O4, which may be attributed to the larger surface area of the magnetite with a smaller particle size. In addition, the amount of functional groups and the surface electrical properties may also affect the adsorption of phosphate to magnetite by influencing the formation of the outer-sphere and/or inner-sphere complexes. The adsorption/desorption of phosphate to/from the magnetite decreases/increases with increasing pH, and the extent of change is more marked for nFe3O4. Increasing the ionic strength of the solution increases the adsorption of phosphate to the two differently sized magnetite particles, whereas the presence of humic acid only increases the adsorption of phosphate to Fe3O4. These trends may be caused by the different extents of change of the surface properties or the dispersion state of the two differently sized magnetite particles under different solution chemistry conditions. The results imply that when the synthesis of magnetite-based materials for phosphate sorption is performed, both the particle size and surface properties should be considered in order to realize the efficient and economical removal of phosphate from wastewater.
TL;DR: The results showed that, the sample that is magnetite free has a diamagnetic response to the applied magnetic field, however the other samples that is loaded with magnetite show super-paramagnetic behavior indicating that the particles' sizes of the magnetite mostly below 20 nm.
TL;DR: In this article, a pilot-scale experiment on the iron recovery from iron ore tailings was investigated using innovative technology of pre-concentration and suspension magnetization roasting (SMR), followed by magnetic separation and flotation.
TL;DR: The abundant presence and chemical multi-fingerprints (including high-resolution structural and elemental fingerprints) of magnetite NPs in the urban atmosphere and the contributions of the major emission sources are reported to support the identification of airborne magnetites pollution nanoparticles as a threat to human health.
Abstract: Nanosized magnetite is a highly toxic material due to its strong ability to generate reactive oxygen species in vivo, and the presence of magnetite NPs in the brain has been linked with aging and neurodegenerative diseases such as Alzheimer's disease. Recently, magnetite pollution nanoparticles (NPs) were found to be present in the human brain, heart, and blood, which raises great concerns about the health risks of airborne magnetite NPs. Here, we report the abundant presence and chemical multifingerprints (including high-resolution structural and elemental fingerprints) of magnetite NPs in the urban atmosphere. We establish a methodology for high-efficiency retrieving and accurate quantification of airborne magnetite NPs. We report the occurrence levels (annual mean concentration 75.5 ± 33.2 ng m-3 in Beijing with clear season variations) and the pollution characteristics of airborne magnetite NPs. Based on the chemical multifingerprints of the NPs, we identify and estimate the contributions of the major emission sources for airborne magnetite NPs. We also give an assessment of human exposure risks of airborne magnetite NPs. Our findings support the identification of airborne magnetite NPs as a threat to human health.
TL;DR: In this paper, typical refractory limonite ore was studied by suspension magnetization roasting and magnetic separation technology, and an iron concentrate with Fe grade of 64.97% and recovery of 94.53% was obtained using a suspension magnetisation roasting - grinding -magnetic separation process.
TL;DR: In this paper, the authors utilized magnetite as an Fe(III) source to enrich the chemolithotrophic sulphur-oxidizing bacteria to proceed the oxidation of the elemental sulphur, which further achieved the whole sulphur cycle.