High Magnetite Content Research Articles

Influence of Technological Factors on the Formation and Transformation of Iron-Containing Phases in the Process of Ferritization of Exhausted Etching Solutions

Every year, metallurgical enterprises generate a massive amount of toxic exhausted high-concentration etching solutions. Application of the ferritization process to recycle exhausted etching solutions can help to prevent environmental pollution. It enables a cost-efficient use of water at an industrial plant and allows the plant to obtain products from toxic industrial waste and utilize it. The aim of the study was to analyze the qualitative and quantitative composition of the formed sediment and its grain size composition. Variable study parameters were the initial pH values of the solutions, the initial concentrations of total iron, and the duration of the aeration process of the reaction mixture. Thermal activation and alternating magnetic fields were used to activate the ferritization. The XRD showed that the formed sediments contained phases of γ-FeOOH, δ-FeOOH, Fe3O4, and γ-Fe2O3. Granulometry analysis showed that these sediments were highly dispersed and heterogeneous. Chemically stable phases of magnetite were obtained in the composition of sediments, with an initial concentration of iron in the reaction mixture of 16.6 g/dm3, a pH of 11.5, and a process duration of 15 min. The study results demonstrated the feasibility of further study and possible use of such sediments with a high magnetite content for the production of materials with ferromagnetic and sorption properties.

Complex refractive index and single scattering albedo of Icelandic dust in the shortwave part of the spectrum

Abstract. Icelandic dust can impact the radiative budget in high-latitude regions directly by affecting light absorption and scattering and indirectly by changing the surface albedo after dust deposition. This tends to produce a positive radiative forcing. However, the limited knowledge of the spectral optical properties of Icelandic dust prevents an accurate assessment of these radiative effects. Here, the spectral single scattering albedo (SSA) and the complex refractive index (m=n-ik) of Icelandic dust from five major emission hotspots were retrieved between 370–950 nm using online measurements of size distribution and spectral absorption (βabs) and scattering (βsca) coefficients of particles suspended in a large-scale atmospheric simulation chamber. The SSA(λ) estimated from the measured βabs and βsca increased from 0.90–0.94 at 370 nm to 0.94–0.96 at 950 nm in Icelandic dust from the different hotspots, which falls within the range of mineral dust from northern Africa and eastern Asia. The spectral complex refractive index was retrieved by minimizing the differences between the measured βabs and βsca and those computed using the Mie theory for spherical and internally homogeneous particles, using the size distribution data as input. The real part of the complex refractive index (n(λ)) was found to be 1.60–1.61 in the different samples and be independent of wavelength. The imaginary part (k(λ)) was almost constant with wavelength and was found to be around 0.004 at 370 nm and 0.002–0.003 at 950 nm. The estimated complex refractive index was close to the initial estimates based on the mineralogical composition, also suggesting that the high magnetite content observed in Icelandic dust may contribute to its high absorption capacity in the shortwave part of the spectrum. The k(λ) values retrieved for Icelandic dust are at the upper end of the reported range for low-latitude dust (e.g., from the Sahel). Furthermore, Icelandic dust tends to be more absorbing towards the near-infrared. In Icelandic dust, k(λ) between 660–950 nm was 2–8 times higher than most of the dust samples sourced in northern Africa and eastern Asia. This suggests that Icelandic dust may have a stronger positive direct radiative forcing on climate that has not been accounted for in climate predictions.

Obtention of magnetite nanoparticles via the hydrothermal method and effect of synthesis parameters

Magnetic nanoparticles (MNPs) have been widely studied for their properties and applications in the fields of electronics and medicine. Hydrothermal synthesis, in which the reaction parameters are extremely important because they influence the product characteristics, properties, and final applications, is an existing method for producing nanomaterials. Therefore, in this study, hydrothermal syntheses were performed to obtain nanomagnetite by varying the temperature, reaction time, and molar ratio, and their influences on the product particle size were analyzed using statistical analysis. The products were characterized in terms of composition and purity.Tthe purest samples were obtained at a reaction temperature of 214 ℃ and the longest reaction time of 6 h, with 96 % purity for the tests with a higher magnetite content. All syntheses produced products with particles on the nanometer scale. The purest magnetite samples exhibited an average hydrodynamic diameter of 220 nm and ferromagnetic behavior. Statistical analysis revealed that the reaction time was the only statistically significant parameter influencing magnetite particle size, with smaller sizes at longer reaction times. The cytotoxicity of MNPs was evaluated in non-tumor cells (NIH3T3 and RAW 264.7). Human erythrocytes did not exert any cytotoxic effects on non-tumor cells, indicating that MNPs are promising drug delivery systems.

Magneto-mineralogical characteristics of mafite-ultramafites of the Middle Bug River area and Holovaniv suture zone of the Ukrainian Shield (overview)

Mafites and ultramafites manifest in the magnetic field as significant magnetic anomalies due to the high content of magnetite, titanomagnetite and iron-magnesium silicates. Studying the mineralogy and magnetic properties of Archean rocks formed deep in the lower crust and uplifted to the surface allows to understanding the sources of magnetic anomalies. Such rocks are known in the Ukrainian shield, in particular in the Middle Bug River region and in the Holovaniv suture zone (HSZ). We consider mafic-ultramafic assemblages of the rocks of this region, their mineral composition and magnetic characteristics, manifestations in the magnetic field, and the distribution of magnetic minerals. Several mafic-ultramafic associations of different ages, composed of effusive, sedimentary-effusive and intrusive formations, are recognized for the area the Pobuzkiy ore mining region. Most of them were transformed intensively by metamorphism of granulite (to eclogite) facies and by intense tectonic and diaphoretic processes. The main volcanics and volcanogenic-sedimentary rocks belong to the Tivriv stratum of the Paleoarchean Dniester-Bug and Neoarchaean Bug series. Mantle rocks were the protolith of the Tivriv stratum, which are similar in composition to oceanic basalts. The Pavliv stratum is considered as a part of the Dniester-Bug series. It is composed mainly of two-pyroxene crystal schists (sometimes amphibolized, often with significant magnetite content (up to 10 %)), magnetite-orthopyroxene crystal schists, and bodies of ferruginous quartzites. Both series contain gneiss complexes, as well as bodies of basite-hyperbasites. Mafic rocks are mainly represented by hornblende-pyroxene crystal schists and amphibolites. Ultramafite and mafit-ultramafite intrusive bodies were mapped in the central and northern parts of the HSZ where they are presented by rocks of the hyperbasite and gabbro-peridotite formations. The Holovaniv block of the HSZ is spatially coincident with the Holovaniv gravitational maximum and magnetic anomalies, which are probably caused by the rooting of mafit-ultramafits from the upper mantle along deep fault zones. Magnetic sources with increased magnetization were identified within the district of Haivoron. They are associated with pyroxene schists, gneisses, coarse-grained pyroxene schists, and ferruginous quartzites. The high values of magnetic parameters of the rocks of the Haivoron-Zavallya region are explained by the presence of eulysites and magnetite-hypersthene crystal schists. Within the area of occurence of charnockite-enderbite rocks, the magnetic field with increased intensity and a large-mosaic structure is observed. Differentiation of the magnetic properties of the rocks of the upper part of the Earth’s crust, the shape and low power of the sources indicate their possible primary magmatic formation in the form of massifs and dykes with further metamorphic transformations. Magnetite is the main magnetic mineral of mafite-ultramafites according to thermomagnetic analysis and ore microscopy. Several generations of magnetite are observed. Early generations (reliably magmatic) are present in the dark-colored minerals as point inclusions and emulsion discharges along fissures (disintegration structures of solid solutions). The increase of the amount of magnetite in all types of rocks is associated with superimposed secondary transformations. Redistribution of iron occurs in the recrystallization zones with the formation of clusters of secondary coarse-grained magnetite. According to the hypothesis, the magnetite of ferruginous quartzites has metamorphic origin, while the origin of the magnetite of iron-carbonate and iron-siliceous formations is a controversial issue. It depends on the determination of the genesis of the original substance.

Structural, Electromagnetic and Microwave Properties of Magnetite Extracted from Mill Scale Waste via Conventional Ball Milling and Mechanical Alloying Techniques.

This study presents the utilization of mill scale waste, which has attracted much attention due to its high content of magnetite (Fe3O4). This work focuses on the extraction of Fe3O4 from mill scale waste via magnetic separation, and ball milling was used to fabricate a microwave absorber. The extracted magnetic powder was ground-milled using two different techniques: (i) a conventional milling technique (CM) and (ii) mechanical alloying (MM) process. The Fe3O4/CM samples were prepared by a conventional milling process using steel pot ball milling, while the Fe3O4/MM samples were prepared using a high-energy ball milling (HEBM) method. The effect of milling time on the structural, phase composition, and electromagnetic properties were examined using X-ray diffraction (XRD) and a vector network analyzer (VNA). XRD confirmed the formation of magnetite after both the magnetic separation and milling processes. The results revealed that Fe3O4 exhibited excellent microwave absorption properties because of the synergistic characteristics of its dielectric and magnetic loss. The results showed that the Fe3O4/CM particle powder had a greater absorption power (reflection loss: <−10 dB) with 99.9% absorption, a minimum reflection loss of −30.83 dB, and an effective bandwidth of 2.30 GHz for 2 mm thick samples. The results revealed the Fe3O4/MM powders had higher absorption properties, including a higher RL of −20.59 dB and a broader bandwidth of 2.43 GHz at a matching thickness of only 1 mm. The higher microwave absorption performance was attributed to the better impedance matching property caused by the porous microstructure. Furthermore, the magnetite, Fe3O4 showed superior microwave absorption characteristics because of the lower value of permittivity, which resulted in better impedance matching. This study presents a low-cost approach method by reutilizing mill scale waste to fabricate a high purity crystalline Fe3O4 with the best potential for designing magnetic nano-sized based microwave absorbers.

Removal of nitrate from radioactive wastewater using magnetic multi-walled carbon nanotubes

In the solidification process using asphalt as a medium, nitrate oxidizes the medium and makes it unstable. Therefore, in order to efficiently remove nitrate from wastewater, a magnetic adsorbent was synthesized (m-MWCNTs), and physicochemical properties of m-MWCNTs were confirmed by SEM, TEM, XRD, FT-IR, BET, and VSM analyses. In the process of synthesizing m-MWCNTs, the amount of magnetite introduced on the surface of MWCNTs could be controlled by increasing the concentration of the chemical agent that becomes the Fe precursor. In addition, the amount of nitrate adsorption increased with higher magnetite content on the surface of MWCNTs. The adsorption process followed the Langmuir model and pseudo-second-order kinetics. In nitrate adsorption using m-MWCNTs, pH was the main condition to determine the adsorption amount, and as the pH increased, the amount of nitrate adsorption decreased. Thermodynamic experiments revealed that the adsorption of nitrate by m-MWCNTs is an endothermic and spontaneous process.

Mineral thermobarometry and its implications for petrological constraints on Mesoarchean granitoids from the Carajás Province, Amazonian Craton (Brazil)

This paper describes the first investigation of the crystallization parameters of the Mesoarchean granitoids from Ourilândia do Norte, which is located in the midwestern part of the Carajás Province. These rocks are divided into three major groups: (i) sanukitoids composed of amphibole-bearing granitoids and associated intermediate to mafic rocks; (ii) potassic granites composed of biotite monzogranites and associated high-Ti granodiorite; and (iii) subordinated TTG-affinity granitoids (amphibole-bearing trondhjemites and biotite-bearing tonalitic xenoliths). These rocks were formed from different sources at different depths, including enriched mantle (sanukitoids), continental crust (monzogranite), mantle-crust mixture (high-Ti granodiorite) and oceanic crust (TTG-affinity granitoids). Potassic granites and porphyritic sanukitoid facies have high magnetite contents, and consequently high magnetic susceptibility (MS), compared to the equigranular sanukitoid facies and trondhjemite. Thermometers based on apatite saturation in whole-rock indicate liquidus temperatures above 800 °C for all granitoids, reaching 959 °C in the high-Ti granodiorite. Amphibole-based and Si-sensitive geothermometers indicate solidus temperatures from 785 to 738 °C for sanukitoids and 892 to 772 °C for trondhjemite, with estimated emplacement pressures varying from 297 to 80 MPa and 580 to 263 MPa, respectively. Because the potassic granites display an amphibole-free assemblage, no geothermobarometric estimate based on amphibole composition was possible. However, potassic granites are associated with coeval sanukitoids (2.88 Ga), which indicates similar pressure conditions and emplacement depths for these rocks. Crystallization constraints from the Ourilândia sanukitoids are comparable to those of the geochemically similar Rio Maria sanukitoids of the Carajás Province, although the pressure estimates and water content show differences. The Fe/(Fe + Mg) ratios of both biotite and amphibole indicate high to intermediate redox conditions for the sanukitoids and potassic granites, which are mostly above that of nickel-nickel oxide (+1.0 < NNO < + 1.9), although less oxidized conditions are estimated for the trondhjemite (– 0.5 < NNO < + 1.0). High water content was estimated for the sanukitoid-related granitoids (> 5%) relative to the TTG-affinity granitoids (< 4%) using amphibole-based water calibrations. Compared with sanukitoids from other Archean cratons, the Ourilândia sanukitoids crystallization constraints show similarities with the more oxidized members from the Baltic Shield, the Closepet-type granites and the Matok-type sanukitoids but differ from the reduced redox conditions of the Elan-type granitoids from the East Sarmatian orogen.

Red‐coated rocks on the seashore: The esthetics and geology of prehistoric rock art in Alta, Arctic Norway

AbstractResearch suggests that the World Heritage rock engravings in Alta, Northern Norway, were made along the seashore over a period of 5000 years. The postglacial rebound and consequent land uplift have caused a continuous displacement of the shoreline, now situating the earliest rock art panels up to 26 m above sea level. By examining the rock surfaces at Hjemmeluft and other sites, using field observations and geological analyses, we found that the pronounced red bedrock surfaces in the current seashore zone are composed of inorganic iron films related to a high content of magnetite in the native sandstone. Coupled with an interpretation of regional environmental history, we also found that it is highly likely that the rock art was originally carved on rocks with red iron films, rocks that are now generally gray. Due to the land uplift and subsequent covering of the rock art with lichen, moss, and turf, the red color has waned at the rock art sites. This knowledge may renew interpretation and understanding of the location of rock art in Alta and may have implications for conservation and management.

Distinct chemical and mineralogical composition of Icelandic dust compared to northern African and Asian dust

Abstract. Iceland is a highly active source of natural dust. Icelandic dust has the potential to directly affect the climate via dust–radiation interaction and indirectly via dust–cloud interaction, the snow/ice albedo effect and impacts on biogeochemical cycles. The impacts of Icelandic dust depend on its mineralogical and chemical composition. However, a lack of data has prevented an accurate assessment of the role of Icelandic dust in the Earth system. Here, we collected surface sediment samples from five major Icelandic dust hotspots. Dust aerosols were generated and suspended in atmospheric chambers, and PM10 and PM20 fractions were collected for further analysis. We found that the dust samples primarily consist of amorphous basaltic materials ranging from 8 wt % (from the Hagavatn hotspot) to 60 wt %–90 wt % (other hotspots). Samples had relatively high total Fe content (10 wt %–13 wt %). Sequential extraction of Fe to determine its chemical form shows that dithionite Fe (Fe oxides such as hematite and goethite) and ascorbate Fe (amorphous Fe) contribute respectively 1 %–6 % and 0.3 %–1.4 % to the total Fe in Icelandic dust. The magnetite fraction is 7 %–15 % of total Fe and 1 %–2 wt % of PM10, which is orders of magnitude higher than in mineral dust from northern Africa. Nevertheless, about 80 %–90% of the Fe is contained in pyroxene and amorphous glass. The initial Fe solubility (ammonium acetate extraction at pH 4.7) is from 0.08 % to 0.6 %, which is comparable to low-latitude dust such as that from northern Africa. The Fe solubility at low pH (i.e. pH 2) is significantly higher than typical low-latitude dust (up to 30 % at pH 2 after 72 h). Our results revealed the fundamental differences in composition and mineralogy of Icelandic dust from low-latitude dust. We attribute these differences to the low degree of chemical weathering, the basaltic composition of the parent sediments and glacial processes. Icelandic dust contributes to the atmospheric deposition of soluble Fe and can impact primary productivity in the North Atlantic Ocean. The distinct chemical and mineralogical composition, particularly the high magnetite content (1 wt %–2 wt %), indicates a potentially significant impact of Icelandic dust on the radiation balance in the subpolar and polar regions.

Source apportionment of magnetite particles in roadside airborne particulate matter

Exposure to airborne particulate matter (PM) is associated with pulmonary, cardiovascular and neurological problems. Magnetite, a mixed Fe2+/Fe3+ oxide, is ubiquitous and abundant in PM in urban environments, and might play a specific role in both neurodegeneration and cardiovascular disease. We collected samples of vehicle exhaust emissions, and of heavily-trafficked roadside and urban background dusts from Lancaster and Birmingham, U.K. Then, we measured their saturation magnetic remanence and used magnetic component analysis to separate the magnetite signal from other contributing magnetic components. Lastly, we estimated the contributions made by specific traffic-related sources of magnetite to the total airborne magnetite in the roadside environment. The concentration of magnetite in exhaust emissions is much lower (3–14 x lower) than that in heavily- trafficked roadside PM. The magnetite concentration in petrol-engine exhaust emissions is between ~0.06 and 0.12 wt%; in diesel-engine exhaust emissions ~0.08–0.18 wt%; in background dust ~0.05–0.20 wt% and in roadside dust ~0.18–0.95 wt%. Here, we show that vehicle brake wear is responsible for between ~68 and 85% of the total airborne magnetite at the two U.K. roadside sites. In comparison, diesel-engine exhaust emissions account for ~7% - 12%, petrol-engine exhaust emissions for ~2% - 4%, and background dust for 6% - 10%. Thus, vehicle brake wear is by far the most dominant source of airborne magnetite in the roadside environment at the two sites examined. Given the potential risk posed, post-inhalation, by ultrafine magnetite and co-associated transition metal-rich particles to human cardiovascular and neurological health, the high magnetite content of vehicle brake wear might need to be reduced in order to mitigate such risk, especially for vulnerable population groups.

Microwave Carbothermic Reduction of Low-Grade Iron Ore

This study evaluates the carbothermal microwave reduction of low-grade banded hematite jasper iron ore for the preparation of potential feedstock for the alternative iron-making process. The coal sample act as transparent material to microwave irradiation at low temperature, however, above 600 °C, an exponential rise in temperature with a heating rate of ~ 220 °C/min was achieved. In contrast, charcoal showed an excellent response to microwaves at low temperatures. It was found that the iron-oxide reduction with coal is lean, resulting in lower metallization; however, the higher magnetite content in the concentrate improves the iron separation efficiency compared to charcoal. The separation efficiency of 67.3 pct is achieved at 6 pct C using coking coal compared to 44.9 pct with charcoal. It is inferred that the coal can be employed as a reductant for microwave carbothermal reduction. The ferrite balls with a yield of ~ 5 pct having 95 pct purity and iron-rich concentrate with ~ 87 emu/g magnetization and ~ 37 pct metallization with 73 pct yield are achieved with 18 pct charcoal in 15 minutes. The chemically bonded hematite and quartz phase enhances the electrical resistance and thus leading to efficient heating compared to the unbonded synthetic mixture. The fayalite formation creates localized melt zones that form’ hot-spots’ for microwaves and enhances the heating rate and, consequently, the reduction kinetics.

A rock magnetic perspective of gas hydrate occurrences in a high-energy depositional system in the Krishna-Godavari basin, Bay of Bengal

We conducted a detailed rock magnetic study complemented by sedimentological and mineralogical methods on a 177.2-m-long sediment core of Hole NGHP-01-14A to constrain the influence of high-energy depositional environment on the magnetic mineral diagenesis and formation of gas hydrates in the Krishna-Godavari (K-G) basin, Bay of Bengal. Five sediment magnetic zones were identified based on the downcore variation in rock magnetic parameters. The magnetic mineralogies comprised of detrital titanomagnetite, diagenetically formed magnetic iron sulfides and their mixture. A distinct magnetically enhanced zone (Z-3) close to a bottom simulating reflector (BSR) is dominated by higher magnetite content, sediment bulk density, and grain size and probably represents several sand-rich sediment layers formed as a result of short-duration intense sedimentation events and got rapidly buried and provided conducive environment for the formation of gas hydrate deposits at the studied site. The concurrence of gas hydrates and high gas saturations within the sand-rich layers (Z-3) suggests that the high-energy depositional environment had a larger control over hydrate formation at Hole NGHP-01-14A. Two magnetic iron sulfide bearing sediment intervals in Z-1b and Z-1c below sulfate-methane transition zone (SMTZ) suggest that their formation is controlled by microbially mediated diagenetic reactions fuelled by presence of gas hydrates and probably represents the fossil gas hydrate zones. We propose that the rock magnetic variations in the studied sediment core at Hole NGHP-01-14A is controlled by both differential loading of detrital magnetic minerals as well as hydrate-induced late diagenetic magnetic iron sulfide formation.

Biocompatible and high-magnetically responsive iron oxide nanoparticles for protein loading

Superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized in this work, featuring uncommonly high magnetization saturation values at room temperature for coated nanoparticles. They also show very low cytotoxicity and promising protein loading efficacy. The ratios of iron(III) acetylacetonate (precursor), benzyl ether (solvent) and oleylamine (surfactant) were changed relatively to those used in the thermal decomposition protocols reported in the literature, in order to enhance the magnetic response of the nanoparticles to an external magnet. The SPIONs were fully characterized in terms of their chemical composition, iron oxide phases, grain/particle sizes and magnetic behaviour. They are predominantly constituted by magnetite, with minor maghemite contributions, as observed by Mössbauer spectroscopy and X-ray diffraction data. The magnetization saturation at room temperature of the best SPIONs achieved 68 emu g−1, which is relevant considering that it corresponds to ∼10 nm sized nanoparticles, where interactions have some significance. This characteristic is mainly due to the high content of magnetite (93% of iron sites) in the nanoparticles and low aggregation provided by their organic coating. In addition, Field-Cooled and Zero Field-Cooled curves allowed to confirm, from the blocking and irreversibility temperatures, the nanoparticle size distribution broadening obtained by Transmission Electron Microscopy.The test of cytotoxicity of the best SPIONs shows very encouraging results for clinical applications, with a half maximal inhibitory (cell viability reduction) concentration (IC50) value as high as 759 μg/mL. Bovine serum albumin protein was loaded on these SPIONs, and very good loading efficacy and capacity of SPIONs for lower concentration of protein was observed, both in water and acetate buffer (pH 5.0), representing these results a successful proof-of-concept for forthcoming studies with therapeutic proteins.

Electronically-Coupled Phase Boundaries in α-Fe2O3/Fe3O4 Nanocomposite Photoanodes for Enhanced Water Oxidation

Photoelectrochemical (PEC) water splitting reactions are promising for sustainable hydrogen production from renewable sources. We report here, the preparation of α-Fe2O3/Fe3O4 composite films via a single-step chemical vapor deposition of [Fe(OtBu)3]2 and their use as efficient photoanode materials in PEC setups. Film thickness and phase segregation was controlled by varying the deposition time and corroborated through cross-section Raman spectroscopy and scanning electron microscopy. The highest water oxidation activity (0.48 mA/cm2 at 1.23 V vs RHE) using intermittent AM 1.5 G (100 mW/cm2) standard illumination was found for hybrid films with a thickness of 11 μm. This phenomenon is attributed to an improved electron transport resulting from a higher magnetite content toward the substrate interface and an increased light absorption due to the hematite layer mainly located at the top surface of the film. The observed high efficiency of α-Fe2O3/Fe3O4 nanocomposite photoanodes is attributed to the close pr...

TCE degradation in groundwater by chelators-assisted Fenton-like reaction of magnetite: Sand columns demonstration

Trichloroethylene (TCE) degradation in sand columns has been investigated to evaluate the potential of chelates-enhanced Fenton-like reaction with magnetite as iron source for in situ treatment of TCE-contaminated groundwater. The results showed that successful degradation of TCE in sand columns was obtained by nitrilotriacetic acid (NTA)-assisted Fenton-like reaction of magnetite. Addition of ethylenediaminedisuccinic acid (EDDS) resulted in an inhibitory effect on TCE degradation in sand columns. Similar to EDDS, addition of ethylenediaminetetraacetic acid (EDTA) also led to an inhibition of TCE degradation in sand column with small content of magnetite (0.5 w.t.%), but enhanced TCE degradation in sand column with high content of magnetite (7.0 w.t.%). Additionally, the presence of NTA, EDDS and EDTA greatly decreased H2O2 uptake in sand columns due to the competition between chelates and H2O2 for surface sites on magnetite (and sand). Furthermore, the presented results show that magnetite in sand columns remained stable in a long period operation of 230 days without significant loss of performance in terms of TCE degradation and H2O2 uptake. Moreover, it was found that TCE was degraded mainly to formic acid and chloride ion, and the formation of chlorinated organic intermediates was minimal by this process.

Optimized Production of Coal Fly Ash Derived Synthetic Zeolites for Mercury Removal from Wastewater

Coal fly ash (CFA) derived synthetic zeolites have become popular with recent advances and its ever-expanding range of applications, particularly as an adsorbent for water and gas purification and as a binder or additive in the construction industry and agriculture. Among these applications, perpetual interest has been in utilization of CFA derived synthetic zeolites for removal of heavy metals from wastewater. We herein focus on utilization of locally available CFA for efficient adsorption of mercury from wastewater. To this end, experimental conditions were investigated so that to produce synthetic zeolites from Kazakhstani CFAs with conversion into zeolite up to 78%, which has remarkably high magnetite content. In particular, the effect of synthesis reaction temperature, reaction time, and loading of adsorbent were systematically investigated and optimized. All produced synthetic zeolites and the respective CFAs were characterized using XRD, XRF, PSA and porosimetric instruments to obtain microstructural and mineralogical data. Furthermore, the synthesized zeolites were studied for the removal of mercury from aqueous solutions. A comparison of removal eficiency and its relationship to the physical and chemical properties of the synthetic zeolites were analyzed and interpreted.

Production and structural, electrical and magnetic characterization of a composite material based on powdered magnetite and high density polyethylene

Se describe la producción y caracterización de un material compuesto basado en matrices de polietileno de alta densidad (HDPE) reforzadas con magnetita pulverizada. Compuestos de este tipo son usados para diferentes aplicaciones como la fabricación de escudos de absorción electromagnética, transductores, entrega focalizada de medicamentos, marcación de órganos, etc. Las muestras fueron producidas de acuerdo a diferentes proporciones en volumen de magnetita y HDPE. Los análisis semicuantitativos llevados a cabo por medio de DRX dejan en evidencia la presencia de hematita al interior de la magnetita mineral usada como refuerzo del compuesto. El porcentaje de cristalinidad de los compuestos se calculó a través de difracción de rayos X. Los resultados de la difracción mostraron una transición amorfo-cristalino del compuesto, debida al creciente contenido de magnetita al interior de la matriz. El porcentaje de cristalinidad (χc) de las muestras reforzadas con un 40% en volumen de magnetita fue del 90% mientras que para las muestras reforzadas con el 10% en volumen la cristalinidad fue del 80%. Esto puede estar ligado a la mayor proliferación de partículas de magnetita al interior de la matriz plástica para contenidos de refuerzo superiores al 30% en volumen, tal y como se evidenció en las imágenes obtenidas a través de microscopía electrónica de barrido (SEM). Las muestras fueron eléctricamente caracterizadas a través de medidas de resistividad volumétrica y polarización eléctrica. Los resultados mostraron que para proporciones del refuerzo de magnetita iguales o inferiores al 20% no hay una reducción substancial en la resistividad de los compuestos comparada con la del polietileno sin reforzar. En cambio, para proporciones de magnetita iguales o superiores al 30% en volumen los compuestos muestran una reducción en la resistividad de hasta seis ordenes de magnitud. La polarización eléctrica deja en evidencia como el material compuesto presenta una transición al pasar de ser completamente aislante (10% en volumen de magnetita) a ser un material resistivo donde la corriente y el voltaje se encuentran en fase (muestras reforzadas con 30%-40% de volumen de magnetita). Las curvas de histéresis magnética en función del campo aplicado muestran un incremento constante en la magnetización de saturación (de 17,3 a 60,5 emu/g) y en la magnetización remanente (de 0.94 emu/g a 5 emu/g), al aumentarse el contenido de magnetita en las muestras. La presencia de hematita en las muestras pudo haber afectado los valores de la magnetización de saturación y de remanencia en las curvas de histéresis magnética. Las curvas de magnetización en función de la temperatura dejan en evidencia la transición de Verwey de la magnetita alrededor de los 120K, a la vez que confirman el aumento en la magnetización de las muestras conforme el contenido del refuerzo aumenta al interior de la matriz. © 2017. Acad. Colomb. Cienc. Ex. Fis. Nat.

Evaluation of a small-diameter sampling method in magnetic susceptibility, AMS and X-ray CT studies and its applications to mafic microgranular enclaves (MMEs) in granite

This paper reviews the technical details of the small diameter sampling method in a study of anisotropy of magnetic susceptibility (AMS) and X-ray CT (computed tomography) and their applications to studies of MMEs (Mafic Microgranular Enclaves) in granite. The AMS results based on 9mm diameter cylinder specimens collected from the Cretaceous Tongkengxi mafic dykes in South China were consistent with results using 25mm diameter specimens. The first case study demonstrated the variation of AMS in the interior of a large MME from South China, which contained a center of strong short-range magnetic lineation. This type of magnetic fabric could be detected only by using sample cores with a small diameter. In the foliation direction, the host granite interacted with the MME more heavily and produced a region with a high magnetite content. The second case study was the investigation of the MMEs in the Early Cretaceous Muchen complex in eastern South China. The MME swarms exhibited relatively uniform magnetic fabrics at the outcrop scale, but the fabrics varied significantly at the intrusion scale. AMS of the MME swarms is coaxial with that of the host granite only at some localities. The disagreement of AMS between MME and host granite either imply different magma flow directions, or different magma flow velocities, or disturbance of the granite fabric by the MME. The MMEs in a mylonitic granite from eastern North China were also studied. The MME specimens show highly variable magnetic susceptibility and lineations. They can be only studied appropriately by a small drill. In the three cases, the three magnetic susceptibility axes of the MMEs are consistent with the volume-weighted maximum eigenvector of long/intermediate/short axes of magnetite. The orientations of the magnetite long axes in the three cases form several modes and the concentration of the modes results in a strong lineation. One implication of this study is that MMEs, with the same magmatic fabrics as their host granite, most likely represent mafic magmas flowing with granitic magmas. Another implication is that the interaction between MMEs and host granite, which is strengthened by magmatic flows or ductile deformations, may promote crystallization of magnetite and formation of magnetite-rich granitoids. The presented 9mm sampling methods provides easy ways to study the petrofabrics and other properties of small-sized features such as MMEs and their detailed internal textures.

Influence of atmospheric pollution on corrosion of materials in Saudi Arabia

ABSTRACTResearch has been carried out for 7 years in eight marine atmospheres with annual average chloride deposition rates of 63–704 mg Cl−/m2 day and sulphur dioxide deposition rates of 6.851–10.887 mg SO2/m2 day. A study of environmental parameters: temperature, relative humidity, airborne chloride and SO2 on the site have been accomplished. Apart from this, the paper also considers the corrosion rates of carbon steel, stainless steel (AISI 304) and galvanised steel and the resulting corrosion products and layers, and their dependence of atmospheric salinity of the site. X-ray diffraction analyses were carried out in order to understand the lepidocrocite and goethite, high akaganeite and magnetite contents of corrosion products. Corrosion rates were determined by weight loss. The aggressive classification was made as per the ISO 9223. Moreover, a technique for calculation of coefficients in the power-linear function for long-term prediction of metal corrosion losses of exposed metals and alloy are presented.

Geneses of Two Types of Mafic Rocks to Carry Placer‐Magnetite Ores in the Sanin Granitic Belt, SW Japan

AbstractTwo types of mafic rocks from the central Sanin district, and their mafic minerals, were studied chemically and microscopically. They are classified into pyroxene‐containing gabbroid and hornblende–biotite quartz diorite. The gabbroid had higher color index but lower magnetite content; while the quartz diorite had lower color index, but higher magnetite content. The magnetite contents are also related to the amounts of hydrous mafic silicates. The gabbroic magma having pyroxene–amphibole assemblage, originated in the upper mantle, was considered essentially anhydrous, but became partly hydrous on the way to the site of solidification in the continental crust, and crystallized some magnetites with hypersthene and amphibole. The quartz dioritic magma was formed by partial melting of possibly subducting ocean‐floor basalts, once exposed to the sea‐floor then altered; thus the magmas became hydrous and oxidized originally, and precipitated abundant magnetite and hydrous mafic silicates from the early crystallization stage onward. Their weathered parts provided the most placer magnetite ores in the history.