High Magnetite Research Articles

Detecting and mapping different types of iron mineralization in Sangan mining region, NE Iran, using satellite image and airborne geophysical data

The Sangan mining region is the largest Fe skarn in western Asia has emplaced into the Khaf-Kashmar-Bardaskan volcano-plutonic belt in the NE Iran. In this region, carbonate rocks of Jurassic skarnified and hosted different epigenetic types of iron minerals, including magnetite, hematite, goethite, and limonite. The combination of remote sensing and airborne geophysical data is a powerful tool for mapping and interpreting iron mineralization in some area with intensely rugged topography or a broad expanse area, where systematic sampling and conventional geological mapping has some limitation and time consuming. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite data and airborne geophysical magnetometry data were used for evaluating and mapping different types of iron mineralization in the Sangan mining region. Preprocessing of the datasets involved band ratio (BR), principal component analysis (PCA), spectral angle mapper (SAM), and constrained energy minimization (CEM) of the visible-near infrared and short wave infrared ASTER data were used to map four types of iron minerals (magnetite, hematite, goethite, and limonite). For preparing a lithological mapp of this region, an RGB image produced by combination of BR and PCA, (R:(5+7)/6, G:PC3, B:PC 5). Implementing SAM and CEM technique were useful for mapping and detecting magnetite, hematite, goethite, and limonite. The Reduce To the Pole (RTP) map of the airborne geophysical magnetometry data is a practical tool for iron ore exploration that were used in this region for enhancing high anomalous signature of magnetite after extracting granitoid rocks. The integration of the extracted information from the ASTER image processing algorithms and geophysical magnetometry, mapped iron mineralization and identified new potential of high magnetite mineralization. The results verified by geological map and comprehensive fieldwork. This integration model can generalize to other arid and semi-arid regions with iron potential for both regional and district scales.

Producing PLGA fine particles containing high magnetite nanoparticles by using the electrospray technique

Loading magnetite (Fe3O4) nanoparticles (NPs), extensively using magnetic agents in magnetic resonance imaging (MRI) and drug delivery in a matrix of polymeric fine particles (FPs), can optimize not only the delivery of these diagnostic and therapeutic agents but also the design of multifunctional drugs. In an effort to use a new method for producing high magnetite loaded polymeric particles, oleic acid (OA) capped magnetite NPs were synthesized and loaded into biocompatible and biodegradable FPs of poly lactic-co-glycolic acid (PLGA) by using the electrospray (ES) technique; and the effect of voltage, flow rate and magnetite content on the morphology, size, size distribution, uniformity and magnetic properties of fabricated magnetic FPs (MFPs) were studied. Results of SEM images and calculations showed that solution flow rate is a major factor in ES and the particle size of magnetite loaded PLGA FPs increases considerably as the flow rate increases. Particle size did not change considerably due to an increase in voltage; however, particle uniformity first increased and then decreased due to an increase in flow rate or voltage. High magnetite content of 72% was achieved for magnetite loaded PLGA FPs and an increase in the magnetite content resulted in an increase in the saturation magnetization of magnetite loaded PLGA FPs; though, their sphericity decreased.

Geochemical and mineralogical characteristics of the Yonghwa phoscorite–carbonatite complex, South Korea, and genetic implications

The Yonghwa phoscorite–carbonatite complex occurs as an isolated individual body with an inclined pipe shape within the Precambrian Gyeonggi Massif, South Korea. The phoscorite consists mainly of olivine, apatite, magnetite, carbonates, amphibole, and phlogopite, and can be subdivided into two types, olivine-rich and apatite-rich. The carbonatite is composed of calcite, Mg-rich dolomite, Fe-rich dolomite, magnetite, apatite, and/or siderite. Intensive fenitization occurred along the boundary between the complex and the wall rocks of leucocratic banded gneiss and garnet-bearing metabasite. The paragenetic sequences of the phoscorite–carbonatite complex demonstrate that the early crystallization of silicate minerals was followed by the crystallization of carbonates as the carbonatitic melt cooled. Magnetite occurs within the complex, and the carbonatites have Fe contents that are higher than typical ferrocarbonatites, due to the high magnetite contents. The rare earth elements (REEs) in the phoscorites and carbonatites are weakly fractionated and show enrichments of LREEs and Nb relative to HREEs. Furthermore, the apatites reflect the fractionated trends of LREEs relative to HREEs. Phoscorite apatites are enriched in Sr and show substitutions between Ca and Sr. Mica chemistry reflects the evolutionary trend of Fe2+ and Mg2+ in the phoscorite–carbonatite melt without Al substitution. Micas exhibit high values of Mg# in the phoscorite–carbonatite complex, but lower values in fenites. Via thermodynamic analysis, the early stability fields of magnetite–pyrrhotite–graphite–carbonate assemblages indicate that the Yonghwa phoscorite and carbonatite crystallized under conditions of 600°C, 2kbar, and XCO2=0.2. Afterward, melts underwent an evolution to the late stability fields of magnetite–pyrite–pyrrhotite–ilmenite assemblages. The δ13C and δ18O isotopic compositions of carbonates in the Yonghwa phoscorite–carbonatite complex are −8.2‰ to −3.4‰ and 6.6 to 11.0‰, respectively, and together with the sulfur isotope compositions of the sulfides (δ34S values of about 0.2‰ to 2.2‰) indicate a primary mantle source of the magmas. Phlogopites from the fenites yielded K–Ar ages of 193.4±4.9 and 195.0±5.1Ma, which demarcate the timing of the cooling of the phoscorite–carbonatite intrusion, and indicate that the phoscorite–carbonatite may be related to a post-collisional magmatic regime. The discovery of this complex marks the first known occurrence in Korea, of Fe and Nb–REE mineralization related to phoscorite–carbonatite igneous activity.

Ferric minerals and organic matter change arsenic speciation in copper mine tailings

Arsenic (As) is commonly associated with Cu ore minerals, with the resultant risk that As can be released offsite from mine tailings. We used synchrotron-based fluorescence X-ray absorption near-edge spectroscopy (XANES) imaging to provide in situ, laterally-resolved speciation of As within tailings which differed in magnetite content (5–12%) and organic matter content (0–5%). Although the total As content was lower in tailings with low magnetite (LM), the soluble (pore water) As was actually 7-times higher in LM tailings than in high magnetite (HM) tailings. Additionally, amendment with 5% sugarcane mulch residues (SMR) (for revegetation) further increased soluble As due to the dissolution and oxidation of arsenopyrite or orpiment. Indeed, in HM tailings, arsenopyrite and orpiment initially accounted for 88% of the total As, which decreased to 48% upon the addition of SMR – this being associated with an increase in AsV-ferrihydrite from 12% to 52%. In LM tailings, the pattern of As distribution and speciation was similar, with As as AsV-ferrihydrite increasing from 57% to 75% upon the addition of SMR. These findings indicate that changes in ore processing technology, such as the recovery of magnetite could have significant environmental consequences regarding the As mobilisation and transformation in mine tailings.

Comparison of the Oxidation Behaviors of High FeO Chromite and Magnetite Concentrates Relevant to the Induration of Ferrous Pellets

Oxidation process plays an important role in producing sufficiently strong ferrous pellets for blast furnace, and the oxidation behavior of pellet feed greatly affects the quality of pellets. As a supplementary research to earlier published work, the present study fixes its particular attention on the fundamental oxidation behavior of a high FeO South African chromite concentrate in comparison to that of typical magnetite concentrate using differential scanning calorimetry, X-ray diffraction analysis, and thermogravimetry at various temperatures ranging from 473 K to 1273 K (200 °C to 1000 °C). The reaction mechanism and phase transformation during the oxidation process of chromite spinel is further explained by thermodynamics calculation performed by FactSage software. Besides, routine laboratory preheating–roasting test of single ore pellets is also conducted to reveal the relevance of oxidizability to the consolidation of pellets. The results show that the chromite spinel possesses much poorer oxidizability than magnetite, usually accompanying complex phase transformations via a preferential nucleation of Fe-rich sesquioxide from the chromite spinel matrix at low temperatures and thereafter the formation of Cr-rich sesquioxide on the substrate of Fe-rich phase at high temperatures. The oxidation of chromite spinel is inferior to that of magnetite from the viewpoint of thermodynamics and dynamic kinetics. Good inherent oxidizability of raw materials is found to have a positive effect on the induration process of pellet.

A magnetite-rich Cyprus-type VMS deposit in Ortaklar: A unique VMS style in the Tethyan metallogenic belt, Gaziantep, Turkey

The Ortaklar VMS deposit is hosted in the Koçali Complex consisting of basalts and deep sea pelagic sediments, which formed by rifting and continental break-up of the southern Neotethyan in Late Triassic. The basalts are of NMORB-type without notable crustal contamination. From the surface to depth, the Ortaklar deposit consists of a gossan zone, a thick massive ore zone and a poorly developed stockwork zone. Primary mineralisation is characterised by distinctive facies including sulphide breccias (proximal), graded beds (distal), stockworks and chimney fragments. Ore mineral abundances decrease in the order of pyrite, magnetite, chalcopyrite, and sphalerite. Two distinct phases of mineralisation, massive magnetite and massive sulphide, are present in the Ortaklar deposit. Textural evidence (e.g., magnetite replacing sulphides) and the spatial relationships with the host rocks indicate that magnetite and sulphide minerals were generated in different stages. The transition from sulphide to magnetite mineralisation is interpreted to relate to variation in H2S content of ore fluids. The 1st stage massive sulphide ore might have formed by early hydrothermal fluids rich in Fe and H2S. The 2nd stage massive magnetite might have formed by later neutral hydrothermal fluids rich in Fe but poor in H2S, replacing the pre-existing sulphide ore.The alteration patterns, mineral paragenesis, lithological features (massive ore-stockwork ore-gossan) of the Ortaklar deposit together with its trace elements, Cu-Pb-Zn-Au-Ag and REE signatures are all consistent with a Cyprus-type VMS system. The δ34S values in pyrite and chalcopyrite samples range from 2.6 to 5.7‰, indicating that the hydrothermal fluids were associated with sub-seafloor igneous activity, typical of Cyprus-type VMS deposits. However, magnetite formed later than sulphide minerals in the Ortaklar deposit, contrasting with typical Cyprus-type VMS deposits where magnetite generally occurs in lower sections. Consequently, although the Ortaklar deposit generally conforms to Cyprus-type deposits, it is distinguished from them by its late stage and high magnetite concentration. Thus, the Ortaklar deposit is thought to be an exceptional and perhaps unique Cyprus-type VMS deposit.

Magnetite recovery from copper tailings increases arsenic distribution in solution phase and uptake in native grass

Reprocessing magnetite-rich copper (Cu) tailings prompted a concern about arsenic (As) risks in seepage water and revegetated plants at Ernest Henry Cu Mine (EHM) in North Queensland, Australia, due to the closely coupled relationship between iron (Fe) minerals and As mobility. The magnetite removal alone significantly decreased the content of crystalline Fe minerals and the maximum arsenate (As(V)) sorption capacity of the resultant tailings. A glasshouse experiment with native grass Red Flinders (Iseilema Vaginiflorum) was conducted with the reprocessed (low magnetite (LM)) and original (high magnetite (HM)) tailings, which were amended with 5% sugarcane residue (SR) as a basal treatment in combination with 0, 1 and 5% pine-biochar (BC). The organic matter treatments and plant growth stimulated the formation of secondary Fe minerals. The amount of extractable amorphous Fe in the amended and revegetated HM tailings was significantly higher than those in the LM. Arsenic forms in the specifically sorbed and the sorbed by amorphous Fe oxides were significantly increased by the SR amendment in the LM tailings, but which were decreased in the HM, compared to the unamended tailings. Soluble As levels in the porewater of the LM under revegetation were significantly higher (300–1150 μg As L−1) than those (up to 45–90 μg As L−1) in HM tailings in the same treatment, which led to the higher As concentrations in the plants grown in the LM tailings. In particular, root As concentration (62–146 mg kg−1) in the LM tailings was almost a magnitude higher than those (8–17 mg kg−1) in the HM. The present results confirmed the initial expectation that the recovery of magnetite from the Cu tailings significantly elevated the risk of As solubility in the tailings by decreasing As sorption capacity and increasing soluble As levels. Thus, it would be beneficial to retain high contents of magnetite in the top layer (e.g., root zone) of the Cu tailings for managing As risk and revegetation in the future.

Designing a large scale synthesis strategy for high quality magnetite nanocrystals on the basis of a solution behavior regulated formation mechanism

The large scale synthesis of magnetite nanocrystals (MNCs) is a sine qua non for supplying the rapidly increasing demand for MNCs in biomedical applications (e.g. magnetic resonance imaging (MRI), magnetic hyperthermia and targeted drug delivery), but it is still difficult to achieve their industrial production due to the operation complexity, strict synthetic conditions and the narrow error tolerance range of existing approaches. Here, we report a facile synthetic procedure using a solvothermal route with an iron acetylacetonate (Fe(acac)3), oleic acid (OA) and oleylamine (OAm) reaction system on a large scale, which is designed under the guidance of the solution behavior regulated formation mechanism of MNCs. Two intermediates, Fe(acac)x(OA)y and N-(cis-9-octadecenyl)-oleamide (OOA), are found to play key roles in adjusting the surface protection status of MNCs and the reducibility of the reaction system. With diverse combinations of surface protection status and reducibility, the final size of MNCs changes from 6.8 nm to 37.4 nm, and the morphology of the MNCs transforms from triangular prismatic to spherical (or quasi spherical), which indicates that the formation of MNCs with distinct sizes and morphologies is attributed to experiencing different pathways from nucleation to growth. Moreover, the reaction system is insensitive to the reaction temperature (220–240 °C) and time (2–6 hours), exhibiting a preferable operation error tolerance range for industrial application. Accordingly, a large scale synthesis is applied for synthesizing high quality MNCs, and 6 grams of spherical and monodispersed MNCs with a diameter of 11.2 ± 0.8 nm are obtained in a single reaction.

Phases Transition and Consolidation Mechanism of High Chromium Vanadium-Titanium Magnetite Pellet by Oxidation Process

Abstract Based on the fundamental characteristics of high chromium vanadium-titanium magnetite (HCVTM), the effects of roasting temperature and roasting time on the phase transition and oxidation consolidation during the oxidation were investigated systematically. It was shown that the oxidation of HCVTM pellet was not a simple process but complex. With increasing roasting temperature and time, the compressive strength of oxidized pellet was improved. The phase transition during oxidation was hypothesized to proceed as follows: (1) Fe3O4 → Fe2O3; (2) Fe2.75Ti0.25O4 → Fe9TiO15 + FeTiO3 → Fe9TiO15 + Fe2Ti3O9; (3) Fe2VO4 → V2O3 → (Cr0.15V0.85)2O3; (4) FeCr2O4 → Cr2O3 → Cr1.3Fe0.7O3 + (Cr0.15V0.85)2O3. The oxidation consolidation process was divided into three stages: (1)oxidation below 1,173 K; (2) recrystallization consolidation at 1,173 – 1,373 K; (3) particle refining recrystallization-consolidation by the participation of liquid phase at 1,373 – 1,573 K. To obtain the HCVTM oxidized pellet with good quality, the rational roasting parameters included a roasting temperature of 1,573 K and a roasting time of 20 min.

Extremely High Phosphate Sorption Capacity in Cu-Pb-Zn Mine Tailings.

Elevated inorganic phosphate (Pi) concentrations in pore water of amended tailings under direct revegetation may cause toxicity in some native woody species but not native forbs or herb species, all of which are key constituents in target native plant communities for phytostabilizing base metal mine tailings. As a result, Pi sorption capacity has been quantified by a conventional batch procedure in three types of base metal mine tailings sampled from two copper (Cu)-lead (Pb)-zinc (Zn) mines, as the basis for Pi-fertiliser addition. It was found that the Pi-sorption capacity in the tailings and local soil was extremely high, far higher than highly weathered agricultural soils in literature, but similar to those of volcanic ash soils. The Langmuir P-sorption maximum was up to 7.72, 4.12, 4.02 and 3.62 mg P g-1 tailings, in the fresh tailings of mixed Cu-Pb-Zn streams (MIMTD7), the weathered tailings of mixed Cu-Pb-Zn streams (MIMTD5), EHM-TD (fresh Cu-stream, high magnetite content) and local soil (weathered shale and schist), respectively. Physicochemical factors highly correlated with the high Pi-sorption in the tailings were fine particle distribution, oxalate and dithionite-citrate-bicarbonate extractable Fe (FeO and Fed), oxalate-extractable Al and Mn, and the levels of soluble Cd and Zn, and total S and Fe. Large amounts of amorphous Fe oxides and oxyhydroxides may have been formed from the oxidation of pyritic materials and redox cycles of Fe-minerals (such as pyrite (FeS2), ankerite (Ca(Fe Mg)(CO3)2 and siderite (FeCO3), as indicated by the extractable FeO values. The likely formation of sparingly soluble Zn-phosphate in the Pb-Zn tailings containing high levels of Zn (from sphalerite ((Zn,Fe)S, ZnS, (Zn,Cd)S)) may substantially lower soluble Zn levels in the tailings through high rates of Pi-fertiliser addition. As a result, the possibility of P-toxicity in native plant species caused by the addition of soluble phosphate fertilizers would be minimal.

Application of Boron-bearing Iron Concentrate to Optimizing Sintering Quality of High Chromium Vanadium-Titanium Magnetite Ore

Application of Boron-bearing Iron Concentrate to Optimizing Sintering Quality of High Chromium Vanadium-Titanium Magnetite Ore

Magnetic and transport properties of epitaxial Fe3O4 films grown at different oxygen pressure

The performance of spintronic devices depends critically on the ability to control the properties of high spin-polarization materials such as magnetite (Fe3O4) in thin films. In this work, the effect of oxygen pressure on the transport and magnetic properties of Fe3O4 thin films was extensively investigated. The 20 nm Fe3O4 films were grown on MgO (001) substrates using molecular beam epitaxy under different oxygen pressure. The quality of epitaxial Fe3O4 thin films was judged by observation of the Verwey transition and corroborated by x-ray photoemission spectroscopy (XPS). In particular, the resistivity measurements showed the Verwey transition to be as sharp as bulk magnetite, which has not been seen in previous studies for film thicknesses less than 30 nm. Therefore, this work provides insight for the growth of ultrathin magnetite films with high crystal quality and sharp Verwey transition. Furthermore, the magnitude of the magnetization change at the Verwey transition was observed to be sensitive to the oxygen pressure during film growth. These results are consistent with the XPS measurements and indicate a relative narrow range of optimal oxygen pressure for the formation of high quality thin magnetite films with electronic and magnetic properties close to bulk Fe3O4.

Airborne chloride deposit and its effect on marine atmospheric corrosion of mild steel

Research has been carried out for one year in six pure marine atmospheres with annual average chloride deposition rates of 70–1906mg Cl−/m2 day. A study of some environmental parameters and their influence in the airborne chloride deposit on the site has been accomplished. The paper also considers mild steel corrosion rate and the resulting corrosion products and layers, and its dependence of atmospheric salinity of the site. In addition to lepidocrocite and goethite, high akaganeite and magnetite contents were found in the corrosion products. Additional magnetite formation is possible due to the transformation of lepidocrocite.

The fate of chromium impurities during acid sulphate digestion of ilmenite concentrates

Ilmenite concentrates from the Murray Basin region of southeastern Australia are contaminated with chromium impurities that must be removed for the ilmenite to become a satisfactory feedstock for the sulphate route to titania pigment production. The chromia is present primarily as discrete, compositionally variable, chrome-rich spinel grains with a smaller amount as intra-grain chromia distributed as coatings in fractures and pores of weathered ilmenite grains. Characterisation of chromia deportment through a simulated acid sulphate digestion process showed a small but non-negligible solubility of the spinels. Most spinels were resistant to dissolution with the exception of those containing high Fe(Al,Cr)2O4 and magnetite (Fe3O4) components. Intra grain chromia was highly soluble. Processing to achieve low bulk chromia using a magnetising roast procedure must ensure that well crystallised rutile is not produced because of its insolubility in the sulphate process. It is also important that the roast conditions do not substantially increase the magnetite content of the spinels making them more susceptible to dissolution. This work highlights the importance of characterising all spinel composition types within ilmenite concentrates in addition to the level of intra-grain chromia associated with the ilmenite when considering the suitability of Murray Basin primary ilmenites as a feedstock to sulphate route titania pigment plants.

Detrital Heavy Mineral Constraints on the Triassic Tectonic Evolution of the West Qinling Terrane, NW China: Implications for Understanding Subduction of the Paleotethyan Ocean

We have examined the Triassic sediments in the west Qinling terrane, northeastern Tibet. These sediments consist mainly of flysch and shallow-sea and fluvial deposits with abundant lithic and heavy mineral detritus, sandwiched between and overlying Late Paleozoic and Early-Middle Triassic ophiolitic mélanges. Volcanic and metamorphic detritus dominates the lithic component of Lower Triassic sandstones accompanied by high Cr-spinel, pyroxene, and magnetite contents, indicating a mixed ophiolite and metamorphic source. Detrital mineral geochemistry further suggests that ophiolitic, high-grade metamorphic, basic, and intermediate-acidic igneous rocks must have been exposed and deeply eroded in their source area. Abundances of zircon, rutile, garnet, tourmaline, and epidote are greater in the Middle Triassic samples, and granitic and volcanic sources are the major contributors of detrital clasts. Considering these new observations on sedimentary petrography and detrital heavy mineral geochemistry, along with published data on paleocurrents, detrital zircon U-Pb ages, sedimentary facies, and regional magmatism, we suggest that these Triassic sediments represent the sedimentary fill of a forearc basin that overlies a late Paleozoic ophiolitic complex. A south-facing Andean-type convergent continental margin system developed along the southern margin of the North China block during the Triassic, in response to northward subduction of the Paleotethyan Ocean.

Increasing magnetite contents of polymeric magnetic particles dramatically improves labeling of neural stem cell transplant populations

Safe and efficient delivery of therapeutic cells to sites of injury/disease in the central nervous system is a key goal for the translation of clinical cell transplantation therapies. Recently, ‘magnetic cell localization strategies' have emerged as a promising and safe approach for targeted delivery of magnetic particle (MP) labeled stem cells to pathology sites. For neuroregenerative applications, this approach is limited by the lack of available neurocompatible MPs, and low cell labeling achieved in neural stem/precursor populations. We demonstrate that high magnetite content, self-sedimenting polymeric MPs [unfunctionalized poly(lactic acid) coated, without a transfecting component] achieve efficient labeling (≥90%) of primary neural stem cells (NSCs)—a ‘hard-to-label’ transplant population of major clinical relevance. Our protocols showed high safety with respect to key stem cell regenerative parameters. Critically, labeled cells were effectively localized in an in vitro flow system by magnetic force highlighting the translational potential of the methods used. From the Clinical EditorUtilizing self-sedimenting polymeric magnetic particles, the authors demonstrate an efficient method for magnetically labeling primary neural stem cells for magnetic localization in the central nervous system.

Alteration-mineralization, and radiometric ages of the source pluton at the Sangan iron skarn deposit, northeastern Iran

The world-class Sangan iron skarn deposit with a proven reserve of>1000Mt iron ore @ 53% Fe, is located in the Khaf-Kashmar-Bardaskan Volcano-Plutonic Metallogenic Belt (KKB-VPMB) of northeastern Iran along the E–W trending regional Doruneh Fault, north of the Lut Block. Skarn mineralization occurs at the contact of the 39.1±0.6Ma to 38.3±0.5Ma Middle Eocene syenite to syenogranite porphyry source pluton with Cretaceous carbonate rocks. The source pluton is part of an I-type, calcalkaline granitoid series with potassium to shoshonitic affinity, metaluminous to slightly peraluminous character. The granitoids are enriched in LILE (Cs, Rb, Ba, K, Th, and U) and LREE (La and Ce), are depleted in HFSE (Nb, Y, Ta, and Ti), HREE (Yb and Lu) and Eu, which together with the low Sr (96 to 362ppm) and (La/Yb)N contents suggest a metasomatized, slab-derived mantel source within the Cenozoic volcanoplutonic continental arc of northeaster Iran. The location of the skarn orebodies is controlled by the regional E–W Doruneh Fault structure, and the spatial distribution and the two, calcic and magnesian, skarns is controlled by the composition of the carbonate protolith that consists of limestone in the west and dolomite in the east. The chemistry of the skarn minerals reflects the composition of the protoliths. The western skarn is dominated by ca-rich calcsilicates that consist of prograde Ca-rich garnet (Adr50–97Grs0–45Sps-Alm2-7), Ca–Fe-rich pyroxene (Hd75.6Di20 Jo4.5), K–Cl–F-bearing Fe–Ca-rich amphibole ferrohastingsite (Fe4.4Ca2Mg 0.5K0.4Na0.3)(Si6.5Al1.8 O22)(Cl, F, OH)2 in endoskarns, and retrograde ferroactinolite (Fe4.2Ca2MgMn0.04Na0.1K0.06)(Si7.8Al0.2O22)(F, Cl, OH)2 and Fe-rich chlorite ripidolite (Fe4.3Mg1.1 Ca0.06Mn0.01)(Al2.8Si3O10)(OH)8 in the exoskarns. Wollasonite, plagioclase, and K-feldspar have been additionally formed together with ferrohastingsite in the endoskarns. The eastern magnesian skarn is typically phlogopite-rich (K0.9Mg2.7Fe0.2 Na0.02)(Si2.9Al1.2O10) (OH, F)2, and consists of prograde forsterite (Fo97.0Fa2.7), diopsidic pyroxene (Hd0.2Di0.88), and retrograde Mg-rich actinolite, Mg-rich chlorite clinochlore (Mg4.5Fe0.1K0.05)(Al1.8Si2.7O10)(OH)8, serpentine and talc. Iron mineralization overprints the calcsilicate skarns in both the western and the eastern skarns and is magnesian in the eastern orebodies (3.65wt.% MgO). The iron ore consists of a number of high grade, replacement, and magnetite orebodies with minor amounts of pyrrhotite, chalcopyrite, and pyrite indicating a large scale metasomatic transfer of iron bearing fluids during Middle Eocene magmatic activity at the KKB-VPMB.

Arsenic Removal by Nanoscale Magnetite in Guanajuato, Mexico

Increasingly, cities in Latin America are recognizing the importance of drinking water quality on public health. A water assessment of Guanajuato, Mexico, and surrounding areas indicated naturally occurring arsenic in some wells above the Mexican drinking water standard of 25 μg/L and the World Health Organization recommendation of 10 μg/L. This initiated a collaborative effort with the city to evaluate a new arsenic removal method using high surface area magnetite sorbents. Nanoscale (20 nm) magnetite particles, previously shown to effectively adsorb arsenic in batch systems, were packed in sand columns to create a continuous treatment process. Design and operating variables were evaluated to confirm that magnetite-to-sand ratio and residence time most significantly affected arsenic breakthrough profiles. Subsequently, a pilot column with 456 g (ca. $2.50 USD) of a commercially available, food-grade magnetite (98 nm effective particle diameter) from a pigment manufacturer demonstrated removal of the equivalent arsenic contained in 1,360 L of Guanajuato groundwater. Although pH reduction dramatically improved arsenic adsorption in batch isotherms, no improvement in arsenic removal efficiency was observed when applied to pilot-scale, field columns in Guanajuato. Interference effects (e.g., from background silica) and changes to surface species over time may impact adsorption differently in column versus batch systems. Overall, this work represents one of the first pilot studies of a nanotechnology-enabled water treatment system, and it demonstrates the potential and additional challenges for taking nanoscale magnetite or other highly researched nanomaterials into a complex full-scale setting.

Effect of a grain-refined microalloyed steel substrate on the formation mechanism of a tight oxide scale

The formation mechanism of tight oxide scale on the microalloyed steel was investigated at temperatures of 550–850°C in dry air. Microstructural characterisations reveal that the spallation of oxide scale dominates at the centre of coarse grains on the oxidation initiation. The fine-grained steel improves the adhesive properties of oxide scale by enhanced grain-boundary diffusion. The lower activation energy and higher oxidation rate accelerate cation/anion migration along grain boundaries, leading to high magnetite content in the oxide scale. The approach by grain refinement at initial oxidation has been proposed to generate the pickle-free tight oxide scale.

Hollow superparamagnetic PLGA/Fe 3O 4 composite microspheres for lysozyme adsorption

Uniform hollow superparamagnetic poly(lactic-co-glycolic acid) (PLGA)/Fe3O4 composite microspheres composed of an inner cavity, PLGA inner shell and Fe3O4 outer shell have been synthesized by a modified oil-in-water (O/W) emulsion-solvent evaporation method using Fe3O4 nanoparticles as a particulate emulsifier. The obtained composite microspheres with an average diameter of 2.5 μm showed excellent monodispersity and stability in aqueous medium, strong magnetic responsiveness, high magnetite content (>68%), high saturation magnetization (58 emu g−1) and high efficiency in lysozyme adsorption.