Natural Iron Oxide Research Articles

Magnetic Study of Fe3O4 Particles for Implementation as Magnetic Fluids

In this work, iron oxide was synthesized by mechanical alloy vibratory disc method. The dependence of magnetic properties on both natural and commercial iron oxide has been studied by using hysteresis loops performed by a vibrating sample magnetometer. The natural oxide phases were determined via X-ray diffraction technique. Magnetic fluid samples were produced by using oleic acid as surfactant and oil as carrier liquid. The viscosity of selected samples was studied at room temperature through rotational viscometer. The results show dependence between the syntheses processes in which the samples were obtained, although experimental results are within those reported in the literature.

Low temperature, non-stoichiometric oxygen-isotope exchange coupled to Fe(II)–goethite interactions

The oxygen isotope composition of natural iron oxide minerals has been widely used as a paleoclimate proxy. Interpretation of their stable isotope compositions, however, requires accurate knowledge of isotopic fractionation factors and an understanding of their isotopic exchange kinetics, the latter of which informs us how diagenetic processes may alter their isotopic compositions. Prior work has demonstrated that crystalline iron oxides do not significantly exchange oxygen isotopes with pure water at low temperature, which has restricted studies of isotopic fractionation factors to precipitation experiments or theoretical calculations. Using a double three-isotope method (18O–17O–16O and 57Fe–56Fe–54Fe) we compare oxygen and iron isotope exchange kinetics, and demonstrate, for the first time, that oxygen-isotope exchange between structural oxygen in crystalline goethite and water occurs in the presence of aqueous Fe(II) (Fe(II)aq) at ambient temperature (i.e., 22–50°C). The three-isotope method was used to extrapolate partial exchange results to infer the equilibrium, mass-dependent isotope fractionations between goethite and water. In addition, this was combined with a reversal approach to equilibrium by reacting goethite in two unique waters that vary in composition by about 16‰ in 18O/16O ratios. Our results show that interactions between Fe(II)aq and goethite catalyzes oxygen-isotope exchange between the mineral and bulk fluid; no exchange (within error) is observed when goethite is suspended in 17O-enriched water in the absence of Fe(II)aq. In contrast, Fe(II)-catalyzed oxygen-isotope exchange is accompanied by significant changes in 18O/16O ratios. Despite significant oxygen exchange, however, we observed disproportionate amounts of iron versus oxygen exchange, where iron-isotope exchange in goethite was roughly three times that of oxygen. This disparity provides novel insight into the reactivity of oxide minerals in aqueous solutions, but presents a challenge for utilizing such an approach to determine equilibrium isotope fractionation factors. Despite the uncertainty from extrapolation, there is consistency in goethite–water fractionation factors for our reversal approach to equilibrium, with final weighted average fractionation factors of Δ18OGth-water=3.0 (±2.5‰) and 0.2 (±0.9‰) at 22°C and 1.9 (±1.5‰) and −1.6 (±0.8‰) at 50°C for nano-particulate and micron-sized goethite, respectively (errors at 2σ level). This variability of Δ18OGth-water with particle size may reflect differences in the grain boundaries of goethite and ratios of surface area to volume. Reaction of ferrihydrite with Fe(II)aq in two distinct waters resulted in a quantitative conversion to goethite and complete oxygen-isotope exchange in each case, and similar fractionation factors were observed for experiments using the two waters. Comparison of our results with previous studies of oxygen isotope fractionation between goethite and water suggests that particle size may be a contributing factor to the disparity among experimental studies.

The role of biochar, natural iron oxides, and nanomaterials as soil amendments for immobilizing metals in shooting range soil.

High concentration of toxic metals in military shooting range soils poses a significant environmental concern due to the potential release of metals, such as Pb, Cu, and Sb, and hence requires remediation. The current study examined the effectiveness of buffalo weed (Ambrosia trifida L.) biomass and its derived biochars at pyrolytic temperatures of 300 and 700 °C, natural iron oxides (NRE), gibbsite, and silver nanoparticles on metal immobilization together with soil quality after 1-year soil incubation. Destructive (e.g., chemical extractions) and non-destructive (e.g., molecular spectroscopy) methods were used to investigate the immobilization efficacy of each amendment on Pb, Cu, and Sb, and to explore the possible immobilization mechanisms. The highest immobilization efficacy was observed with biochar produced at 300 °C, showing the maximum decreases of bioavailability by 94 and 70% for Pb and Cu, respectively, which were attributed to the abundance of functional groups in the biochar. Biochar significantly increased the soil pH, cation exchange capacity, and P contents. Indeed, the scanning electron microscopic elemental dot mapping and X-ray absorption fine structure spectroscopic (EXAFS) studies revealed associations of Pb with P (i.e., the formation of stable chloropyromorphite [Pb5(PO4)3Cl]) in the biomass- or biochar-amended soils. However, no amendment was effective on Sb immobilization.

Conversion of extra-heavy Ashal’chinskoe oil in hydrothermal catalytic system

The products of hydrothermal catalytic conversion of extra-heavy Ashal’chinskoe oil at temperatures of 210, 250, and 300°C in a closed system with different amounts of water in the presence of the natural catalyst iron oxide (hematite) have been studied. It has been shown that the degradation of high-molecular-mass components of the extra-heavy oil, such as benzene- and alcohol-benzene-extractable resins and asphaltenes, leads to a generation of new light fractions that were absent in the initial crude oil. A difference between the oil components in stability to the conversion processes has been shown. The most significant changes are observed for the reduction in the amount of alcohol-benzene resins, which is accompanied by an increase in aromaticity and the extent of oxidation. In asphaltenes, the concentration of free radicals (R*) increases and the concentration of tetravalent vanadium (V+4) decreases, changes that are accompanied by enhancement of structure carbonization and a reduction in their molecular mass. It has been shown that coking includes the step of formation of asphaltenes followed by the conversion of a part of them into high-carbon-content toluene-insoluble substance of the carbene and carboid type, which precipitate together with coke from the petroleum disperse system when a certain concentration is reached. Changes in the structure of the hematite catalyst has been also revealed.

Interactions between natural organic matter, sulfur, arsenic and iron oxides in re-oxidation compounds within riparian wetlands: NanoSIMS and X-ray adsorption spectroscopy evidences

Arsenic (As) is a toxic and ubiquitous element which can be responsible for severe health problems. Recently, Nano-scale Secondary Ions Mass Spectrometry (nanoSIMS) analysis has been used to map organomineral assemblages. Here, we present a method adapted from Belzile et al. (1989) to collect freshly precipitated compounds of the re-oxidation period in a natural wetland environment using a polytetrafluoroethylene (PTFE) sheet scavenger. This method provides information on the bulk samples and on the specific interactions between metals (i.e. As) and the natural organic matter (NOM). Our method allows producing nanoSIMS imaging on natural colloid precipitates, including 75As−, 56Fe16O−, sulfur (32S−) and organic matter (12C14N) and to measure X-ray adsorption of sulfur (S) K-edge. A first statistical treatment on the nanoSIMS images highlights two main colocalizations: (1) 12C14N−, 32S−, 56Fe16O− and 75As−, and (2) 12C14N−, 32S− and 75As−. Principal component analyses (PCAs) support the importance of sulfur in the two main colocalizations firstly evidenced. The first component explains 70% of the variance in the distribution of the elements and is highly correlated with the presence of 32S−. The second component explains 20% of the variance and is highly correlated with the presence of 12C14N−. The X-ray adsorption near edge spectroscopy (XANES) on sulfur speciation provides a quantification of the organic (55%) and inorganic (45%) sulfur compositions. The co-existence of reduced and oxidized S forms might be attributed to a slow NOM kinetic oxidation process. Thus, a direct interaction between As and NOM through sulfur groups might be possible.

Oxidation Kinetics of Thin and Ultrathin Fe Films

We have studied oxidation kinetics of Fe thin lms under atmospheric conditions using the fact that metallic iron is a ferromagnet but ultrathin natural iron oxides are practically nonmagnetic at room temperature. As a consequence, oxidation is associated with a loss in ferromagnetism. Fe thin lms were deposited onto 1.5 nm V thick bu er layer using UHV magnetron sputtering. As a substrate we have used Si(100) wafers with an oxidised surface. Results show that all samples with an initial Fe thickness greater than 6 nm oxidize practically instantaneously, whereby a constant amount of 2.5 nm of metal is transformed into oxides. For iron thickness lower than 6 nm the time constant for oxidation increases considerably reaching a value of 30 days for the initial Fe thickness equal to 4 nm.

Preparation and Properties of Porous Composite of Hematite/Magnetite/Carbon with Eucalyptus Wood Biotemplate

By using eucalyptus wood biotemplate, a novel porous composite material of iron oxides and carbon (PC-Fe/C) was manufactured for adsorption of oxoanion pollutants. The material's microstructure and characteristic were investigated by different characterization techniques. The experimental results show that the PC-Fe/C composite mainly consisted of hematite, magnetite, and carbon, and preserved the porous hierarchical texture of the wood with 70 ∼ 120 µm macropores, 4.1 ∼ 6.4 µm mesopores, and 0.1 ∼ 1.3 µm micropores. Its Brunauer-Emmtee-Teller (BET) surface area was 59.2 m2 g−1. The maximum adsorption capacities were 2.49, 2.96, and 0.69 mg g−1 for arsenic(V), chromium(VI), and phosphorus(V), respectively. The adsorption capacities of the unpulverized material as a novel filtration adsorbent are comparable to fine particles of the pulverized material, natural, and synthetic iron oxides.

Fuel Oil Production from Two-Stage Pyrolysis-Catalytic Reforming of Brominated High Impact Polystyrene Using Zeolite and Iron Oxide Loaded Zeolite Catalysts

The experiments of two-stage pyrolysis and catalytic reforming of high impact polystyrene (HIPS) containing brominated flame retardants and antimony trioxide (Sb2O3) were conducted in the presence of four zeolite catalysts in order to remove the bromine content from the derived oil products. The four catalysts used were natural zeolite (NZ), iron oxide loaded natural zeolite (Fe-NZ), HY zeolite (YZ) and iron oxide loaded HY zeolite (Fe-NZ). The effect of catalyst types on the product yield, the gas and oil product composition and the debromination efficiency of the oil products was evaluated in details. The results showed that the loading of iron oxides reduced the pore size and surface areas of natural zeolite and HY zeolite. Regardless of the presence of catalysts, the single-ring aromatic compounds were the main components of the oil products, such as ethylbenzene, toluene, styrene and cumene. Meanwhile, when YZ and Fe-YZ were used, the two-ring and multi-ring aromatic compounds in the oils, as well as the yield of gas products, significantly increased at the expense of valuable single-ring aromatic compounds. Furthermore, in terms of the debromination performance of the oil products, Fe-NZ and Fe-YZ were better than NZ and YZ, duo to the loading of iron oxide, which could react with derived HBr and then remove more bromine from the oil products.

Synthesis of Magnetite Nanoparticles by Top‐Down Approach from a High Purity Ore

This study attempts to synthesize magnetite nanoparticles from a high purity natural iron oxide ore found in Panvila, Sri Lanka, following a novel top‐down approach. Powder X‐Ray diffraction, elemental analysis, and chemical analysis data confirmed the ore to be exclusively magnetite with Fe2+ : Fe3+ ratio of 1 : 2. Surface modified magnetite nanoparticles were synthesized by destructuring of this ore using a top‐down approach in the presence of oleic acid. These oleic acid coated nanoparticles were further dispersed in ethanol resulting in stable nanomagnetite dispersion. Interestingly, the nanoparticles demonstrated a spherical morphology with a particle size ranging from 20 to 50 nm. Magnetic force microscopic data was used to confirm the topography of the nanoparticles and to study the magnetic domain structure.

Surface Complexation Modelling of Arsenic and Copper Immobilization by Iron Oxide Precipitates Derived from Acid Mine Drainage

Acid mine drainage (AMD) constitutes a serious environmental problem in mining areas due to the acidification of soils and aquatic systems, and the release of toxic metals. Many of the pollutants that occur in AMD display a high affinity for the surfaces of the aluminium and iron oxides that are typically present in systems affected by AMD. This binding affinity reduces the mobility of trace metals and metalloids, such as copper and arsenic, thus helping to mitigate contamination of aquatic systems. In the present study, water samples and iron-rich bed sediments were collected in areas affected by copper mining activities. A loose ochre-coloured precipitate occurring on the banks of a river close to an abandoned tungsten and tin mine was also sampled. The composition of the precipitate was established, and adsorption experiments were performed with copper and arsenate ions to determine the ability of natural iron precipitates to reduce the concentration of these ions in solution. Surface complexation models provided a good description of the behaviour of natural iron oxides in terms of copper and arsenate retention. Use of this type of model enables prediction of the distribution of pollutants between the solid and solution phases and analysis of their mobility in relation to environmental conditions (pH, ionic strength, presence of competing species, etc.).

On the inhibition of metal transfer through ion implantation

The impact of N+, C+, and S+ ion implantation on Al metal transfer to the implanted Interstitial Free Steel (ISF) was investigated using single-pass wear tests. The metal transfer was quantified by evaluating the Al coverage area from EDS maps taken from the wear tracks. The ISF steel had three different dose levels from each ion. It was concluded that S+ implantation provided the best resistance to metal transfer. The metal transfer resistance increased with dose for all the implanted species except for the S+ where the results plateaued after a 1e17 ions/cm2 dose due to sputter limitations. Argon purging reduced the effectiveness of the N+ and C+ implants in reducing metal transfer while having little effect on the S+ implantations. This indicates that the N+ and C+ implanted ISF steel wear elements rely on tribo-oxidation to optimize their metal transfer resistance effectiveness while tribo-oxidation provides no benefit for the S+ implantations. In all cases, ion implantation increased the amount of tribo-oxidation taking place where C+ and S+ showed increasing amount of oxygen take-up with dose. The N+ implantations showed little dependence of oxygen take-up with dose, which indicates that the C+ and S+ implantations alter the low-temperature oxidation kinetics differently than the N+ implantations. The friction coefficient did not depend on oxygen concentration in the environment, which enforces the importance of surface film chemistry for friction generation. The tribochemical reduction of the natural iron oxide by aluminum facilitates metal-on-metal contact, and creates the adhesion forces responsible for the measured friction coefficient whose generation is characterized by a stick-slip mechanism. Ion implantation reduced the friction and noise with the sulfur implantations providing the best benefit. The mechanisms for the reduction of metal transfer based on surface chemistry were proposed from the view point of Sasada’s Mutual Material Transfer model.

Iron oxide waste to clean arsenic-contaminated water

Serious cases of arsenic toxicity of people drinking water have led to the development of water purification methods. For instance, arsenic can be removed from water by adsorption on natural iron oxides. The use of iron oxide from waste could decrease the cost and recycle iron. Here, we studied arsenic removal from contaminated water using iron oxide wastes from a pickling unit of a steel plant. This iron oxide was reduced to magnetic iron oxide in a fluidised bed reactor. We tested arsenic removal from As-spiked solutions and from contaminated waters from West Bengal. Results showed more than 90 % arsenic removal within 10 min. The arsenic concentration of contaminated waters was decreased from 0.010–0.018 to 0.002–0.008 mg/L. We also found that the occurrence of SO4 2−and PO4 3− decreased arsenic adsorption. Iron oxide waste is therefore a new low-cost and effective arsenic adsorbent to clean water.

Modeling oxyanion adsorption on ferralic soil, part 2: Chromate, selenate, molybdate, and arsenate adsorption

High levels of oxyanions are found in the soil environment, often as a result of human activity. At high concentrations, oxyanions can be harmful to both humans and wildlife. Information about the interactions between oxyanions and natural samples is essential for understanding the bioavailability, toxicity, and transport of these compounds in the environment. In the present study, the authors investigated the reactivity of different oxyanions (AsO4 , MoO4 , SeO4 , and CrO4 ) at different pH values in 2 horizons of a ferralic soil. By combining available microscopic data on iron oxides with the macroscopic data obtained, the authors were able to use the charge distribution model to accurately describe the adsorption of these 4 oxyanions and thus to determine the surface speciation. The charge distribution model was previously calibrated and evaluated using phosphate adsorption/desorption data. The adsorption behavior on ferralic soil is controlled mainly by the natural iron oxides present, and it is qualitatively analogous to that exhibited by synthetic iron oxides. The highest adsorption was found for arsenate ions, whereas the lowest was found for selenate, with chromate and molybdate ions showing an intermediate behavior.

Goethite colloid enhanced Pu transport through a single saturated fracture in granite

α-FeOOH, a stable iron oxide in nature, can strongly absorb the low-solubility plutonium (Pu) in aquifers. However, whether Pu transports though a single saturated fracture can be enhanced in the presence of α-FeOOH colloids remains unknown. Experimental studies were carried out to evaluate Pu mobilization at different water flow velocity, as affected by goethite colloids with various concentrations. Goethite nanorods were used to prepare (α-FeOOH)-associated Pu suspensions with α-FeOOH concentration of (0–150) mgL−1. The work experimentally evidenced that α-FeOOH colloid does enhance transport of Pu through fractured granites. The fraction of mobile 239Pu (RPu, m=41.5%) associated with the α-FeOOH of an extremely low colloid concentration (0.2mgL−1) is much larger than that in absence of α-FeOOH (RPu, m=6.98%). However, plutonium mobility began to decrease when α-FeOOH concentration was increased to 1.0mgL−1. On the other hand, the fraction of mobile Pu increased gradually with the water flow velocity. Based on the experimental data, the mechanisms underlying the (α-FeOOH)-associated plutonium transport are comprehensively discussed in view of its dynamic deposition onto the granite surfaces, which is decided mainly by the relative interaction between the colloid particle and the immobile surface. This interaction is a balance of electrostatic force (may be repulsive or attractive), the van der Walls force, and the shear stress of flow.

Heterogeneous photodegradation of 1-naphthol with natural iron oxide in water: influence of oxalic acid

The transformation of 1-Naphthol (1-NP) photoinduced by a natural iron oxide (NIO) in aqueous suspension and the influence of oxalic acid have been investigated under monochromatic irradiation (365 nm). The NIO was characterized by X-ray diffraction (XRD), X-ray fluorescence, and Brunauer–Emmett–Teller methods. The XRD result shows that the NIO consists of mixed crystalline hematite. A dark investigation of the system was performed before studying the photochemical behavior. The experiment shows that the NIO possesses a high adsorption capacity for 1-NP and its photodissolution was not observed. Also, the experiment shows that the UV light alone could play an important role in the degradation of 1-NP.After 3 h of irradiation at pH 9.4, 64.2% of 1-NP was degraded. The presence of the NIO was found to promote the photodegradation of 1-NP (72.1%) and the process follows pseudo-first-order reaction kinetics. The photodegradation of 1-NP has been studied at different pH (1.9–12) and catalyst loads (0.5–2.0g L−1). The results demonstrated that the phototransformation of 1-NP is enhanced by increasing the pH and the optimal initial concentration of the catalyst was found to be 1 g L−1. The involvement of •OH radicals was ruled out because of the non-influence of tertiobutanol used as a scavenger. The effect of the oxalic acid on the photodegradation of 1-NP by NIO was also investigated. The result revealed that the oxalic acid promoted the photodegradation rate of 1-NP. This investigation will give a new insight to understand the 1-NP photodegradation in natural environment. Measuring chemical oxygen demand also monitors the toxicity of the degraded 1-NP solution and a significant decrease is observed, which implies that the photodegradation through NIO is a safer technique.

Process integration for hydrogen production, purification and storage using iron oxides

Hydrogen production from natural gas using a Ni-based catalyst and its later hydrogen storage with some synthetic and natural iron oxides are presented. The Ni-based catalyst showed high methane conversion, close to the equilibrium one, when producing hydrogen from methane through catalytic partial oxidation (CPO) and wet-CPO with a low steam to carbon ratio (0.5). The solid solution formation observed in the Ni-based catalyst could have enhanced its stability. The iron oxides capacity for hydrogen storage was analysed with reduction–oxidation cycles at 973 K and atmospheric pressure. The natural oxides presented structural modifications, mainly due to sinterization, which negatively affected their storage capacity and stability.

Effect of different factors on low temperature degradation of hematite iron ore during reduction

Low temperature degradation (LTD) of iron oxides was investigated with the aim of understanding how natural iron ores degrade under different conditions. Minimisation of this degradation would increase the acceptance level of natural iron ores as feed materials without prior beneficiation. In addition to temperature and reduction gas composition, sample positioning in the reduction furnace and sample’s original weight were also found to influence LTD. Samples placed in the top reaction zone of the furnace, which have the first contact with the reducing gas, were found to degrade 1.5 times more than those in the middle and bottom reaction zones. In addition, they presented a wide range of size in the disintegrated particles than those in the middle and bottom reaction zones. Furthermore, the samples with an original weight equal to or greater than 5 g, had a disintegration extent of less than 10%. Therefore, if the reduction gas comes into contact with a certain material first, before contacting the iron oxide, it may serve to reduce on LTD during reduction. Furthermore, in laboratory conditions, the occurrence of low temperature breakdown of the natural iron oxides can be minimised by using samples with an original weight equal to or greater than 5 g.

Magnetically-modified natural biogenic iron oxides for organic xenobiotics removal

Biogenic iron oxides have been collected from a water stream and subsequently magnetically modified using water-based magnetic fluid. Both natural and magnetically modified materials have been characterized in detail using wavelength dispersive X-ray fluorescence spectrometry, X-ray powder diffraction, Mossbauer spectroscopy, electron microscopy and BET surface area measurements. The natural material is composed of 2-line ferrihydrite, forming hollow microtubules—sheaths of Leptothrix ochracea, and detrital components. As a result of the ferrofluid modification, maghemite nanoparticles were identified on the surface of the treated material. The active surface area of the bulk, magnetically-modified sample was 148 m2 g−1. The magnetically modified material was tested as inexpensive magnetically responsive adsorbent for the removal of selected organic xenobiotics, namely organic dyes, from aqueous solutions. The observed maximum adsorption capacities ranged between 34.3 and 97.8 mg of dye per 1 g of adsorbent.

Optical characteristics and photothermal conversion of natural iron oxide colloid

Abstract Background Chemical compositions and spectroscopic characteristics of the natural floating colloids in brine mineral water were investigated in this study. Methods The natural colloidal materials were investigated using electron microscopy, X-ray crystallography, elemental analysis, and absorption and emission spectroscopies. Results The natural colloidal particles have a spherical shape, with average diameter of 200 nm, and amorphous crystalline structure. The colloids are mostly composed of iron and oxygen atoms; they also contained small amounts of trace elements and rare earth minerals. In particular, the colloids show remarkable absorption and emission characteristics in the wide spectral region from ultraviolet (UV) to near infrared (NIR), which could make it useful in photoconversion and hyperthermal applications. Conclusion From the photothermal conversion efficiency measurement using an infrared thermography under irradiation of visible and NIR light, interestingly, it was found that the natural colloids have higher photothermal conversion efficiency, as compared with those of several different-typed minerals.

Quantification of Al-goethite from diffuse reflectance spectroscopy and magnetic methods

As one of the most abundant iron oxides in soils, the presence and nature of goethite is controlled by the soil conditions and burial history. The visible diffuse reflectance spectroscopy (DRS) is a useful tool for quantifying goethite. However, aluminium (Al) substitution for goethite is very common in soils and the effects of Al content on the DRS properties of goethite have not been fully resolved. In this study, two series of Al substituted goethites (Al-goethite) and 20 Chinese loess/palaeosol samples were investigated using both DRS and magnetic methods to test the feasibility of quantifying Al-goethite with the DRS method. Results show that the peak positions and amplitudes of the goethite DRS band are significantly influenced by Al substitution. Specifically, the goethite concentration proxy, the amplitude of the DRS band, is relatively stable only when Al substitution ranged between about 4 and 16 mol per cent. Practically, in order to resolve the difficulty in measuring Al content in natural samples, the unblocking temperature (Tb) is proposed as the proxy for Al substitution of goethite. When Tb of Al-goethite was above 250 K, the amplitude of DRS can be used to reliably trace the goethite concentration variation in natural samples. For example, the DRS spectra for the Chinese loess–palaeosol samples support the idea that only haematite is enhanced via pedogenesis. In contrast, the origin of goethite seems to be mostly related to the aeolian inputs.