Types Of Iron Oxides Research Articles

Scorodite synthesis process using solid iron oxides

The immobilization of arsenic in the form of scorodite (FeAsO4·2H2O), which has excellent chemical stability, is attracting attention as a method for treating wastewater containing high concentrations of arsenic generated at nonferrous metal smelting plants. Scorodite, with its low solubility and high arsenic content per volume, is expected to be an environmentally friendly arsenic fixation method suitable for final disposal. Various scorodite synthesis methods have been studied. The first synthesis method proposed is the hydrothermal method using an autoclave to synthesize highly crystalline scorodite. Although the hydrothermal method is capable of synthesizing scorodite with good crystallinity, from an economic point of view, scorodite synthesis under ambient pressure and at low temperatures is more attractive. As a low-temperature scorodite synthesis method under atmospheric pressure, the oxidation of Fe(II) process by O2 bubbling was proposed. In this method, ferrous sulfate is added to an arsenic-containing solution as a Fe ion source, and in situ oxidation of Fe(II) by O2 or air bubbling to form scorodite with good crystallinity. In addition to temperature, other conditions, pH, Fe/As ratio, and reaction time have been reported to affect scorodite crystallization. Recently, scorodite synthesis using solid iron oxide as the Fe source for scorodite synthesis, instead of aqueous Fe salt solutions, has attracted much attention. In this presentation, we will report on the investigation of reaction parameters, such as the type of iron oxide and reaction temperature, for the scorodite synthesis using solid iron oxide.

Size-selective attachment of polyvinyl chloride microplastics on iron oxides in aqueous environments

The interaction of microplastics (MPs) with mineral particles is a crucial process determining the fate of MPs in aquatic environments, but potential size-selective interaction of MPs with minerals is unknown. In this work, strong and multi-layered attachment of a mix of heterogeneously size of polyvinyl chloride (PVC) MPs was observed on all the four types of iron oxides, following an order of Fe3O4-i > Fe3O4-s > γ-Fe2O3 > Fe3O4-n. Electrostatic attraction dominated their strong attachment, while hydrogen bonding and halogen bonding also contributed to MPs-mineral interaction. Importantly, both attachment rates and capacities were more favorable for large-sized PVC MPs (> 1.0 μm) than small-sized MPs (0.6–1.0 μm), due to more available attachment sites and stronger electrostatic attraction. Large-sized MPs preferred to detach from iron oxides before small-sized MPs, confirming by configuration analysis. The attachment accelerated the sedimentation of PVC MPs, while a fraction (i.e., 26.7 %, PVC/iron oxide ratio at 0.2:1) of heteroaggregates floated at the air–water interface associated with bubbles. Natural organic matter decreased MPs-mineral interaction due to competitive adsorption, electrostatic repulsion, and steric hindrance, while the attachment was enhanced with increasing ionic strengths (0–200 mM). These findings contribute to a better understanding of the transport and fate of MPs in aquatic systems.

Comparison of different iron oxides for degradation of tetracycline anti-bacterial drug

Abstract Nanomaterials have a wide range of applications including novel biomedical studies are devoted to improving the functionality and effectively of traditional and unmodified systems, both drug carriers and common scaffolds for tissue engineering or advanced hydrogels for wound healing purposes. In this regard, metal oxide nanoparticles show great potential as versatile tools in biomedical science. In particular, iron oxide nanoparticles with different shape and sizes hold outstanding physiochemical characteristics, such as high specific area and structure that make them unique nanomaterials to be used in diverse aspects of medicine and biological systems. The challenges associated with the uncontrolled presence of antibiotics such as tetracycline in the environment have necessitated their removal through different techniques. Tetracycline is hard to degrade in living organisms and can even be converted to more toxic substances. In this article different type of iron oxides were subjected to photo degradation of antibacterial drug Tetracycline under UV light illumination and direct sunlight and the results were promising to degrade the drug within 20 min. The SEM, TEM, EDAX and XRD for the catalyst were characterized to confirm the presence of iron oxide, the size and shape of the particle. The kinetics of photo degradation of tetracycline followed the pseudo-first-order mechanism, proceeding through hydroxyl radicals generated under illumination. Moreover, the photo generated hydrogen peroxide could lead to heterogeneous photocatalytic processes on the surface of iron oxide nanoparticles; additionally generating hydroxyl and hydroperoxyl radicals enables photo degradation of tetracycline.

Dissemination of antibiotic resistance genes is regulated by iron oxides: Insight into the influence on bacterial transformation

The transportation of antibiotic resistance genes (ARGs) in manure-soil-plant continuums poses risks to human health. Horizontal gene transfer, particularly for bacterial transformation, is an important way for ARG dissemination. As crucial components in soils, iron oxides impacted the fates of various abiotic and biotic contaminants due to their active properties. However, whether they can influence the transformation of ARGs is unknown, which waits to be figured out to boost the assessment and control of ARG spread risks. In this study, we have investigated the effects of goethite, hematite, and magnetite (0–250 mg/L, with sizes < 100 nm and > 100 nm) on the transfer of ampicillin resistance genes to Escherichia coli cells. At lower iron oxide concentrations, the transformation of ARGs was first facilitated (transformation frequency reached up to 3.38-fold higher), but the facilitating effects gradually weakened and eventually disappeared as concentrations further increased. Particle size and iron oxide type were not the universal determinants controlling the transformation. At lower concentrations, iron oxides interacted with proteins and phospholipids in E. coli envelope structures, and induced the overgeneration of intracellular reactive oxygen species. Consequently, they led to pore formation and permeability enhancement on the cell membrane, thus promoting the transformation. The facilitation was also associated with the carrier-like effect of iron oxides for antibiotic resistance plasmids. At higher concentrations, the weakened facilitations were attributed to the aggregation of iron oxides. In this study, we highlight the crucial roles of the concentrations (contents) of iron oxides on the dissemination of ARGs in soils; this study may serve as a reference for ARG pollution control in future agricultural production.

Metal oxide/chitosan composite for organic pollutants removal: A comprehensive review with bibliometric analysis

Organic pollutants are now a global concern because of their rapid increase following the rapid industrial growth. In tackling this problem, researchers have used chitosan that could act as adsorbing material. However, chitosan use in wastewater treatment requires further modification owing to its drawbacks of being susceptible to acidic environment and mechanically weak. Of many modifying approaches, metal-oxide embedment is perceived as promising because not only does it improve the chemical and physical properties of chitosan, but it also adds new features to the material such as being magnetic or photocatalytic. This present review describes the modification of chitosan through metal oxide embedment aiming to its utility in organic waste removal. Firstly, the definition of chitosan and the progress of its application in wastewater treatment are presented. Types of metal oxides, namely photocatalyst and magnetic iron oxide are also discussed. Embedment of metal oxides into chitosan could be done using methods such as sol-gel, high-energy ball milling, and spray-drying, where they affect the chemical and physical properties of the produced metal oxide/chitosan composites. Reported studies suggest a high percentage of organic pollutant removal, up to 100%. In addition to its removal ability, metal oxide/chitosan is also proven to be environmentally friendly and economical.

Spectroscopic methods in the analysis of wear particles

Detailed characteristics wear particles formed in various brake pads were done. Our study was focused on identification structure and chemical composition of powder particles released by brake abrasion. The experimental studies were carried out using Mössbauer spectroscopy, X-ray powder diffraction, scanning electron microscopy and magnetic measurements. Structure and chemical composition of the original brake pads and disc samples were compared with the results obtained for wear particles. The chemical and phase composition of wear particles is in large part similar to composition of the original brake pads. Wear particles contained mainly various types of iron oxides, iron and iron carbon metallic particles. The part of the wear particles showed paramagnetic behaviour at room temperature. The sample with fully paramagnetic wear particles behaviour was subjected low temperature Mössbauer and magnetic measurements. The results indicate transition interval corresponding to magnetically ordered states—ferro/antiferromagnetic.Graphic abstract

Determination of the percentage of magnetite in iron oxide nanoparticles: A comparison between mössbauer spectroscopy and Raman spectroscopy

Nanomaterials and especially iron oxide nanoparticles become more common for several fields such as data storage or biomedical applications. For these biomedical applications, iron oxide nanoparticles with a superparamagnetic state are the most used as cancer treatment, contrast agent for MRI … To obtain a superparamagnetic state, the iron oxide must be less than 20 nm in size. It exists several types of iron oxide with a superparamagnetic behaviour: magnetite (Fe3O4) and maghemite (γ-Fe2O3). For the biomedical fields, the magnetic behaviour must be maximal, therefore the iron oxide synthesised in a preferential way is magnetite. A microwave process is carried out because this synthesis allows to obtain monodisperse nanoparticles with a narrow size distribution and a good crystallinity. However, the quantity of magnetite in our samples is not known exactly. The goal of this study is to determine the amount of magnetite in our samples. The most accurate technique to determine the proportion of magnetite is Mössbauer spectroscopy. A study of our samples with this technique is carried out and is compared to another technique which is Raman spectroscopy. In this work, iron oxide nanoparticles synthesised with a microwave process are characterized by Transmission Electronic Microscopy, X-Ray Diffraction, magnetic measurements, Mössbauer spectroscopy and Raman spectroscopy.

Assessment of heat transfer and the consequences of iron oxide (Fe3O4) nanoparticles on flow of blood in an abdominal aortic aneurysm

The present study is established on a simulation using CFD analysis in COMSOL. Blood acted as the base fluid with this simulation. The taken flow is been modeled as incompressible, unsteady, laminar and Newtonian fluid, which is appropriate at high rates of shear. The characteristic of flow of blood is been studied in order to determine pressure, velocity and temperature impact caused by an abdominal aortic aneurysm (AAA). This work employs nanoparticles of the Iron Oxide (Fe3O4) type. The CFD technique is utilized to evaluate the equations of mass, momentum, and energy. The COMSOL software is utilized to generate a normal element sized mesh. The findings of this study demonstrate that velocity alters through aneurysmal part of the aorta, that velocity is higher in a diseased segment, and that velocity increases before and after the aneurysmal region. For the heat transfer feature, the reference temperature and general inward heat flux is taken as 293.15K and 800W/m2. The nanoparticles altered blood's physical properties, including conductivity, dynamic viscosity, specific heat, and density. The inclusion of Iron Oxide (Fe3O4) nanoparticles managed to prevent overheating because taken nanoparticles have significant thermal conductivity. These findings will be extremely beneficial in the treatment of abdominal aortic aneurysm.

Effects of iron oxide contents on photocatalytic performance of nanocomposites based on g-C3N4

α-Fe2O3/Fe3O4/g-C3N4 nanocomposites were prepared in-situ by solution combustion as magnetically separable photocatalysts using ferric nitrate as oxidant, glycine as organic fuel, and g-C3N4. The effects of various amounts of iron oxides, on the magnetic, optical, and photocatalytic properties were explored by different characterization methods. The magnetite (Fe3O4) phase as ferrimagnetic material disappeared with the increase in ferric nitrate contents, leading to the decrease of magnetic properties. The bandgap energy decreased from 2.8 to 1.6 eV with the increase of the hematite (α-Fe2O3) phase.The photocatalytic results showed that the type and amount of iron oxides had a significant effect on the decolorization of methylene blue, rhodamine B and methyl orange dyes under visible-light irradiation. The activity of the nanocomposite sample containing 37 wt. % iron oxides was more effective than that of the pristine g-C3N4 sample to photodegrade the methylene blue, rhodamine B and methyl orange, respectively. Moreover, the nanocomposites exhibited a higher photocurrent density than that of the pristine g-C3N4, mainly due to their lower charge recombination rate.

Simultaneous stabilization of Pb, Cd, and As in soil by rhamnolipid coated sulfidated nano zero-valent iron: Effects and mechanisms.

Sulfidation effectively improves the electron transfer efficiency of nanoscale zero-valent iron (nZVI), but decreases the specific surface area of nZVI. In this study, sulfidated nZVI (S-nZVI) coated with rhamnolipid (RL-S-nZVI) was synthesized and used to stabilize Pb, Cd, and As in combined polluted soil. The stabilization efficiency of 0.3% (wt) RL-S-nZVI to water soluble Pb, Cd, and As in soil reached 88.76%, 72%, and 63%, respectively. Rhamnolipid coating inhibited the reduction of specific surface area and successfully encapsulated nZVI, thus reducing the oxidation of Fe0. The types of iron oxides in RL-S-nZVI were reduced compared to S-nZVI, but the content and strength of Fe0 iron were obviously enhanced. Furthermore, rhamnolipid functional groups (-COOH and -COO-) were also involved in the stabilization process. In addition, the stabilization efficiency of RL-S-nZVI to the bioavailable Pb, Cd, and As in soil increased by 41%, 41%, and 50%, respectively, compared with nZVI. The presence of organic acids, especially citric acid, improved the stabilization efficiency of RL-S-nZVI to the three metals. The result of BCR sequential extraction indicated that RL-S-nZVI increased the residual state of Pb, Cd, and As and reduced the acid-soluble and reducible state after 28 days of soil incubation. XRD and XPS analyses showed that the stabilization mechanisms of RL-S-nZVI on heavy metals involved in ion exchange, surface complexation, adsorption, co-precipitation, chemisorption, and redox.

The synthesis and super capacitive characterization of microwave-assisted highly crystalline α-Fe2O3/Fe3O4 nanoheterostructures.

A facile microwave-assisted solvothermal process for the synthesis of narrow-size distributed α-Fe2O3, α-Fe2O3/Fe3O4, and Fe3O4 nanostructures was demonstrated using PVP as a surfactant. During the reaction, the influence of the reaction media, such as the mixture of ethylene glycol and water on the formation of α-Fe2O3, α-Fe2O3/Fe3O4, and Fe3O4 was systematically studied. Interestingly, pure aqueous medicated solvothermal reaction conferred phase pure rhombohedral Fe2O3 (hematite) and linearly upsurging the formation of cubic Fe3O4 (magnetite) with the increasing concentration of EG and further, in pure EG, it deliberated cubic Fe3O4. FESEM and FETEM images of α-Fe2O3/Fe3O4 nano heterostructure clearly showed the nanosized Fe3O4 particles of 4-6 nm decorated onto Fe2O3 nanoparticles. Further, the electrochemical properties of α-Fe2O3, α-Fe2O3/Fe3O4, and Fe3O4 nanoparticles were investigated with galvanostatic charge-discharge and cyclic voltammetry measurements using a 3-electrode system. The findings show that their specific capacitances are linked to the type of iron oxide. More significantly, the α-Fe2O3/Fe3O4 nanoheterostructure exhibited the utmost capacitance of 165 F g-1, which is greater than that of pristine α-Fe2O3 and Fe3O4. Enhancement in the electrochemical performance was found due to the improved charge transfer that occurred at the interface of the nanoheterostructure. The nanoparticles of Fe3O4 deposited on the Fe2O3 increased the active sites, which accelerated the process of adsorption and desorption of ions, thereby enhancing the interface-assisted charge transfer and reducing the internal resistance, which is ultimately responsible for enhanced capacitance. Such heterostructures of nano iron oxide may fulfill the requirements of electrodes in supercapacitors.

A Simulation Study on Electrical and Thermal Properties of Nanofluids Based Mineral Oils for Potential Transformer Applications

The present report demonstrates the efficacy and capabilities of transformer oil due to their growing demand for the production of good insulation. In this work, we have enhanced the electrical and thermal properties of nanofluid (NF)-based mineral oils using the Quickfield simulation in the presence of the different types of nanoparticles (NPs), namely, magnesium oxide (MgO), titanium dioxide (TiO2), and iron oxide (Fe3O4), which are classified based on their conductivity. Different concentrations of NPs of 1%, 5%, and 10% have been used to prepare the NFs. The test cell model and the dummy model of a three-phase transformer have been designed to investigate the electrical and thermal properties of the NFs. It is found that the addition of NPs enhanced both the electrical and thermal properties of the fluid. The voltage at the center of the electrodes decreased by 46% in the case of TiO2 at the highest percentage concentration (10%) of NPs, while for the same concentration of MgO and Fe3O4, it is reduced by 18% and 24%, respectively, whereas the temperature of the oil decreased by approximately 20%, for all NFs at the highest concentration (10%). It is envisaged that the method used can be very useful in determining the properties of NPs before testing them in real life.

The effect of iron oxide types on the photochemical transformation of organic phosphorus in water

Iron oxides play an important role in the transport and transformation of organic phosphorus in aquatic environments. However, the effect of different types of iron oxide on the environmental fate of organic phosphorus has remained unclear. In this study, the photodegradation of the organic phosphorus compound adenosine triphosphate (ATP) via the activity of crystalline (goethite) and amorphous (ferrihydrite) iron oxides was investigated. It was found that ATP was photodegraded by goethite, resulting in the release of dissolved inorganic phosphate under simulated sunlight irradiation. The concentration of ATP on goethite decreased by 75% after 6 h of simulated sunlight irradiation, while the concentration of ATP on ferrihydrite decreased by only 22%. ATR-FTIR spectroscopy revealed that the intensity of the peaks for the P–O and PO stretching vibrations in the goethite−ATP complex decreased significantly more after simulated sunlight irradiation than did those for the ferrihydrite treatment. Combined with the higher TOC/TOC0 values for the goethite treatment, the results indicate that a more vigorous photochemical reaction took place in the presence of goethite than with ferrihydrite. Reactive oxygen species analysis also showed that hydroxyl and superoxide anion radicals were generated when goethite was exposed to simulated sunlight irradiation, while ferrihydrite did not exhibit this ability. Overall, this study highlights that the type of iron oxide is an important factor in the transformation of organic phosphorus in aquatic environments.

Photocatalytic oxidation activity enhanced by iron-oxalate chelates for Fenton-like oxidation of As(III) in oxalate systems

This study investigated the Fenton-like oxidation of As(III) by three types of iron oxides in oxalate systems. The effects of pH, oxalate concentration and atmosphere on the oxidation of As(III) by iron oxide photocatalyst were studied. Firstly, hydrothermal carbon (HTC) was used as the carrier to load three kinds of iron oxides to prepare new composite materials, including α–FeOOH, αFe2O3 and Fe3O4, which can solve the dispersion problem of iron oxide by using a large number of rich functional groups on the HTC surface. The experiment results showed that under the conditions of O2, pH = 5.0 and oxalate concentration of 0.5 mmol·L1, As(III) was completely oxidized by α–FeOOH and α–Fe2O3 at 15 min and 20 min, respectively. Density functional theory (DFT) was used to study the surface adsorption energy of iron oxide and oxalate. The calculated results showed that the order of adsorption energy of three iron oxides for the oxalate is αFeOOH > αFe2O3 > Fe3O4. FeIII(C2O4)+, a mononuclear bidentate iron oxalate chelate with the strongest photosensitivity, was constructed in the Fe-Oxalate system containing only Fe(III), resulting in the photocatalytic efficiency of α–FeOOH and αFe2O3 was superior to that of Fe3O4. These findings contribute to arsenic remediation of water bodies by using iron materials and oxalate in the natural environment.

The Effect of Soil Amendments on Trace Elements’ Bioavailability and Toxicity to Earthworms in Contaminated Soils

The aim of this study was to assess the impact of soil amendments, characterized by different sorption properties, on the effectiveness of trace elements’ (Cu, Zn, Pb, Cd, Ni, and Cr) stabilization and bioavailability to earthworms. The study was conducted as a microcosm experiment using soil derived from a heavily contaminated post-industrial area. The Eisenia veneta earthworm was cultured for 4 weeks in soils amended with materials characterized by different properties, origins, and potential effects on limiting the availability of metals in soils: two type of compost (Zabrze compost-ZC; GWDA compost-GC), two types of biosolid (Bełchatów biosolids-BB, Grabów biosolids-GB), calcium phosphate (CP), iron oxide (IO), bentonite (BE), rock waste (RW), and limestone (CC). After the incubation, the biomass and survival numbers of the earthworm species decreased significantly (p &lt; 0.05). The accumulation of metals in the earthworm tissues expressed by the bioaccumulation factor value (BSAF) were dependent on the type of amendment applied to the soil. The highest decrease in the earthworms’ weight and survival rate was caused by compost (72%) and bentonite (33%), while the lowest was caused by the rock waste (10%) and iron oxide (11%). The biosolids exhibited the greatest toxicity, causing the mortality of all the earthworms. The accumulation of metals in earthworm tissues and the BSAF value were dependent on the type of amendment applied to the soil. The BSAF for the contaminated soil by Cd decreased to the greatest extent after the addition of ZC (by 57%), GC (55%), CP (41%), and IO (37%). A similarly positive effect was noted for Pb after IO addition (45% decrease). The Zn, Cr, and Ni concentration in earthworms, contrary to other elements, increased, regardless of the amendment. The results showed that the applied soil amendments were characterized by varying potential for the reduction in the metal bioavailability in the soil, depending on their composition and physicochemical properties. Moreover, earthworms may exhibit a diversified response to soil amendments as a result of the impact of amendment on the metal forms in soils and their direct impact on organisms. Generally, the Cd was easily transferred from the soil into and accumulated in the earthworm tissues. Our study confirms that this element creates the highest risk for the trophic chain in soils affected by the Zn and Pb smelting industry. Moreover, greater Zn supply reduces the accumulation of Cd in animal bodies. This study provides valuable practical knowledge on the short-term biological effects of a range of soil amendments in metal-contaminated soils.

Experimental Investigation of Methane Generation in the Presence of Surface and Un-Surface Nanoparticles of Iron Oxide

The exploitation and harnessing of renewable energies are becoming increasingly important throughout the world. This study presents a method of methane (CH4) generation using biological disintegration of food waste (FW) by anaerobic digestion (AD). The CH4 production was enhanced by the addition of three different types of iron oxide (Fe3O4) nanoparticles (NPs) (Cetyletrimethlebromide (CTAB), urea-capped Fe3O4 NPs and Fe3O4 NPs without capping). The bio generation of CH4 and biodegradation of volatile solids (VS) were carried out in an AD treatment at mesophilic conditions (35–37 °C) for more than 50 days in batch mode. The concentration of all three types of NPs was kept constant at 75 mg/L. It was noticed that urea-capped NPs produced the maximum CH4 (5.386 L), followed by Fe3O4 NPs (5.212 L). Methane production in the control bioreactor was 2.143 L. The experimental results of CH4 generation (a dependent variable) were analyzed against the concentrations of NPs used (as independent variables) in multiple regression analysis (MRA). The overall model for the experiments resulted in R2 and R-adjusted values of 0.995 and 0.993, respectively.

Effect of Aggregate Gradation and Filler Content on the Rutting Resistance of Modified Colored Hot Mix Asphalt

Rutting is considered as the most generated distress in Iraqi roads as a result of the high temperature and excessive traffic load. So, it is essential to utilize polymer modified binder to increase the performance of pavements. The objective of this paper is to assess the effect of aggregate gradation and filler content on the rutting formation of Colored Hot Mix Asphalt CHMA. The HMA was colored by using iron oxide as filler to produce red HMA. Two blends were used: fine and coarse with two different types of filler iron oxide for CHMA and limestone for conventional HMA with two filler content 6% and 10%. Neat (AC 40-50) and modified asphalt (AC 40-50 + 4%SBS) were used. Tests are held on adding 4% Styrene Butadiene Styrene )SBS( by the weight of neat asphalt (AC 40-50) to raise the performance grade by two grades from PG (64-16) to PG (76-16) [1] and [2]. The wheel tracking test is used to assess the rut depth of the CHMA. The test results showed that the using iron oxide with neat asphalt increase the rut depth resistance by 200 and 400 failure load cycles than mixtures using limestone (cycles that mix reach 25 mm rut depth) for fine and coarse mix respectively. Also, the effect of gradation shows that the fine mixture fails at 4000 cycles while the coarse mixture fails at 1800 cycles for 6% limestone mixtures. Increasing the iron oxide content from 6% to 10% leads to increase the failure load cycles by 2200 and 1200 cycles for fine and coarse mixture respectively using modified asphalt. The fine mixture with 10% iron oxide using modified asphalt gives the best performance with 7000 cycles than the coarse mixture with 10% filler content and modified asphalt with 4000 cycles. irrespective the filler and type of binder, the dense mixtures using iron oxide as filler exhibit better resistance to rutting formation than coarse mixtures.

Fe–Ti mineralization conditions during melt differentiation in intermediate zone

The article provides a detailed description of Fe-Ti mineralization in the layered (differentiated) bodies of the Misaelga complex (Southern Ural). Various morphogenetic types of iron and titanium oxides are described: segregation &lsquo;drop&rsquo;, monomineral precipitates of ilmenite, magnetite, and various ilmenitemagnetite intergrowths and decay structures. The chemical composition of magnetite (in wt.%): TiO2 (from 0.13 to 14.27), Al2O3 (from 0.51 to 21.36), Cr2O3 (from 0.48 to 24.07), MgO (from 0.11 to 6.41), MnO (from 0.05 to 1.0), V2O5 (from 0.23 to 1.16), ZnO (from 0.8 to 5.78), NiO (from 0.13 to 0.73), SiO2 (from 0.52 to 2.75), CaO (0.51) and ilmenite: Cr2O3 (from 0.13 to 1.27), MgO (from 0.27 to 5.5), MnO (from 0.14 to 3.51), V2O5 (from 0.14 to 0.37), Al2O3 (3.0) and NiO (1.4). It is shown that chromium and magnesium in magnetite and ilmenite are present only in the minerals of the picrite horizon, where transitional magnetite &rarr; chrommagnetite and ilmenite &rarr; picroilmenite varieties are formed as a result of heterovalent isomorphism. Based on the calculation of crystallization temperatures, it was found that segregation of the ore melt occurred at T above ~ 1200 &deg;C; the crystallization temperature of ilmenite&ndash;magnetite intergrowths was 712&ndash;745 &deg;С, and the decay temperature of the solid solution varied within 588&ndash;766 &deg;С. It is concluded that the segregation and gravitational deposition of ore minerals are not antagonistic but are realized at certain stages of the evolution of the melt. Moreover, the mechanisms of localization of the ore substance in a limited volume are governed by the physicochemical parameters and thermobaric conditions of the environment of mineral formation during ore genesis existing in a particular volume of the melt during its crystallization.

Iron Oxide and Water Paste Rheology and Its Effect on Low Adhesion in the Wheel/Rail Interface

The “wet-rail” phenomenon results in low adhesion between wheel and rail throughout the year, occurring transiently on a slightly wet, or drying railhead. It has been previously proposed that it is caused by a mixture of iron oxides and small amounts of water (from dew or precipitation) on the railhead that form a friction reducing paste. This paper outlines a novel combination of rheology, modelling and experimental work using a twin disc test rig to determine how the rheology of this iron oxide paste affects adhesion. The yield strength of different types of iron oxides, along with solid oxide fraction of the friction reducing paste, was assessed and used as an input into an “adhesion model” for assessing water and oxide suspensions. The rheological and modelling results were compared against very low adhesion recorded in twin disc experimental validation when simulating the wet-rail phenomenon.

Biogeochemical properties and potential risk of shallow arsenic-rich sediment layers to groundwater quality in Western Bangladesh.

The arsenic-contaminated groundwater has attracted attention in much south and southeast Asian deltas, however, mainly on the deep aquifers. Here, arsenic (As) concentration and its fractionation of the sediment cores in a shallow aquifer in Bangladesh were investigated using ICP-MS, FE-EPMA, XRD and 14C-AMS chronology techniques. The results of the present study indicated that the peak concentrations of As (54.7-79.1µg/g) were in peat layers (at a depth of 7.5-8.0m). Several types of iron (oxyhidr)oxides and framboidal pyrite, which contain As also, were found in the peat samples. The high concentrations of As were in an exchangeable form, As-bearing iron crystalline and As-bearing organic materials. We revealed that the As-rich peat layers were formed from 3170 to 3901cal yrs before, due to the sea level decrease in this area. The 16S rRNA gene-based phylogenetic analysis revealed that the bacterial strains in the As-rich peats were mainly affiliated with genera Acinetobacter, Enterobacter, Escherichia, Bacillus, Clostridiaceae and Acinetobacter. The geo-accumulation index (Igeo) and ecological risk index assessment were calculated for the sediments, which shows that As-rich sediment layers were in range of moderately to heavily contaminated and considerable classes, respectively. Under the permanent saturated condition, the As-rich peat layers should be considered as an important potential driver of the groundwater As in this area.