Magnetite Content Research Articles

Chemical and mineralogical characterization to define parameters for comminution, aiming at granulometric adequacy in rock rich in feldspars extracted in Pedra Lavrada-PB

The demand for high purity feldspars with low contaminant content, especially for use in the manufacture of porcelain tiles and white crockery, poses a challenge for processing the ore. Due to the need for very low iron levels, less than 0.15%, operations must be more complex, costly and capable of providing a high purity final product. To this end, it is necessary to employ mineralogical and technological characterization to understand the ore and plan the operations of the processing plant. A sample of rock rich in feldspars collected in an extraction in the municipality of Pedra Lavrada/PB was studied, aiming to identify the chemical composition and release spectrum using XRD and SEM techniques. Aliquots were subjected to preparation, granulometric classification and high-intensity wet magnetic separation steps. The results indicate that the rock has high concentrations of feldspars, quartz and a significant content of magnetite and hornblende. The physical release of magnetic mineral phases occurs below 0.104mm, and fragmentation operations must be designed with this grain size standard in mind. Magnetic separation, with mass recovery of 14.01% in relation to the feed, satisfactorily guaranteed a reduction in the concentration of magnetic minerals in the ore

Magnetic particle detection as a surface soil source pollution in urban areas: Implication from magnetic and geochemical analysis along the major port city in China

The global concern for the level and sources of urban surface soil pollution has been increasing. In this study, we assessed the efficacy of the environmental magnetic method in identifying the sources of urban surface soil pollution in Ningbo, a prominent city in China. To achieve this, magnetic and geochemical measurements were performed on surface soil samples collected from 114 designated sites， supplemented by polarizing microscope observations. The mass-specific magnetic susceptibility values (χlf) exhibited a wide range, spanning from 25.45 to 1903.85 × 10−8m3kg−1, with an average of 295.45 × 10−8m3kg−1. Notably, lower magnetite concentrations were identified in the urban center, contrasting with higher values observed in the peripheral industrial areas. The average concentrations of Cu, Pb, Zn, and Ca were much higher than the background values. Anthropogenic sources such as traffic emissions, construction dust, and industrial processes emerged as the predominant contributors to surface soil pollution in Ningbo. Fuzzy cluster analysis was employed to discern possible relationships between magnetic properties and pollution sources. The results indicated three categories of pollution. Cluster 1 is related to natural (lithogenic and pedogenic) magnetic mineral sources, and the samples contained abundant quartz or feldspar. Notably, these samples are largely unpolluted. Cluster 2 is associated with a combination of natural and anthropogenic sources. Cluster 3 is dominated by spherical magnetic particles formed by high-temperature combustion. In Cluster 3 topsoil samples, ascertained to be contaminated through magnetic analysis, a significant Spearman correlation was observed between magnetic parameters and Cu, Cr, and Fe. In conclusion, magnetic properties provide a swift and effective method for characterizing surface soil pollution in Ningbo, enabling the tracing of sources for trace metals in the surface soil.

Hydrogen in magnetite from asteroid Ryugu

AbstractIn order to gain insights on the conditions of aqueous alteration on asteroid Ryugu and the origin of water in the outer solar system, we developed the measurement of water content in magnetite at the micrometer scale by secondary ion mass spectrometry (NanoSIMS) and determined the H and Si content of coarse‐grained euhedral magnetite grains (polyhedral magnetite) and coarse‐grained fibrous (spherulitic) magnetite from the Ryugu polished section A0058‐C1001. The hydrogen content in magnetite ranges between ~900 and ~3300 wt ppm equivalent water and is correlated with the Si content. Polyhedral magnetite has low and homogenous silicon and water content, whereas fibrous magnetite shows correlated Si and water excesses. These excesses can be explained by the presence of hydrous Si‐rich amorphous nanoinclusions trapped during the precipitation of fibrous magnetite away from equilibrium and testify that fibrous magnetite formed from a hydrous gel with possibly more than 20 wt% water. An attempt to determine the water content in sub‐μm framboids indicates that additional calibration and contamination issues must be addressed before a safe conclusion can be drawn, but hints at elevated water content as well. The high water content in fibrous magnetite, expected to be among the first minerals to crystallize at low water–rock ratio, points to the control of water content by local conditions of magnetite precipitation rather than large‐scale alteration conditions. Systematic lithological variations associated with water‐rich and water‐poor magnetite suggest that the global context of alteration may be better understood if local water concentrations are compared with millimeter‐scale distribution of the various morphologies of magnetite. Finally, the high water content in the magnetite precursor gel indicates that the initial O isotopic composition in alteration water must not have been very different from that of the earliest magnetite crystals.

Effects of chloride on corrosion scale compositions and heavy metal release in drinking water distribution systems

Variations in water chemistry may lead to the release of harmful heavy metals in drinking water distribution systems (DWDSs). In this study, the effects of chloride on the release of heavy metals such as Fe, Mn, As, Cr, Mo, V, Sr, and Co were examined using steel and cast iron pipe loops. After chloride was added, the relative contents of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and siderite (FeCO3) in pipe scales increased, but the contents of magnetite (Fe3O4) decreased. The most prevalent compounds were α-FeOOH and γ-FeOOH. When the chloride levels were increased, the effluent concentrations of Fe, Mn, As, Cr, Mo, V, Sr, and Co significantly increased. These heavy metals were released presumably because of the destabilization and dissolution of corrosion scales induced by chloride and adsorption site competition. Strong positive correlations were also observed between Fe&Mn, Fe/Mn&As, Fe/Mn&Cr, Fe/Mn&Mo, Fe/Mn&V, Fe/Mn&Sr, and Fe/Mn&Co, indicating the co-release of Fe, Mn, and other metals. This study may be helpful for the potential strategies on avoidance of heavy metal release and improvement of water supply security.

Kinetics of spontaneous phase transitions from wüstite to magnetite in superparamagnetic core-shell nanocubes of iron oxides.

Iron oxide nanoparticles with a wüstite structure have been prepared by thermal decomposition. In air, they undergo a spontaneous transition into a thermodynamically more stable magnetite structure that grows from the surface. The thickness of this magnetite shell increases with time, thereby producing a series of core-shell nanoparticles. We investigated the kinetics of this phase transition in 23 nm nanocubes using time-resolved XRD, from which the fractions of individual phases were determined by the Rietveld refinement. This kinetics is described theoretically using three coupled reaction-diffusion master equations for the concentrations of oxygen, wüstite, and magnetite, in which both the diffusion of oxygen and its reaction with wüstite are thermally activated. The coefficients of these terms were adjusted so that the predictions of the model reproduce the XRD data at 298 K and 353 K, whereas the predictive capability of the model was assessed by comparing its predictions with measurements at 403 K.

Electromagnetic modulation of conductance and susceptance in electrical devices based on silicone oil with polypyrrole–magnetite particle composites

Electrical conductance and susceptance of electrical devices with composite liquids based on silicone oil and polypyrrole-magnetite particles are finely tuned by varying electric and magnetic fields and adjusting magnetite content.

Effect of Fe3O4:RGO Ratios in Magnetic Nanocomposites Applied for Dye Discoloration

Nanocomposites of magnetite anchored on reduced graphene oxide with different magnetite:reduced graphene oxide mass ratios were synthesized and evaluated in indigo carmine photo Fenton discoloration. All nanocomposites are magnetic and showed comparable amounts of magnetite and hematite with a higher level of hematite for low iron contents. The highest value of 63.6 emu g-1 was obtained for the nanocomposite with the highest magnetite content. The nanocomposites presented high dispersion of iron oxide particles, at about 12 nm on reduced graphene oxide surface sheets. The samples also showed bandgap energies below that found for bulk magnetite, showing an important effect of reduced graphene oxide. The nanocomposite with an iron nitrate precursors mass ratio of 17:1 showed the best performance (99.7% of indigo carmine discoloration (2.1 × 10-5 mol L-1) at 30 min of reaction, hydrogen peroxide(2.3 × 10-1 mol L-1), and a catalyst dosage of 0.67 g L-1). Reusability tests were performed, and this nanocomposite was shown to be active for at least three recycles. X-ray photoelectron spectrum of Fe2p3/2 showed that the FeIII/FeII ratio was maintained even after three recycles (4 runs), meaning that reduced graphene oxide is responsible for stabilizing magnetite particles, thus maintaining its photocatalytic activity.

Genesis of Sulfide Mineralization in the Gallala Area Kurdistan Region, Iraq: Constraints from Major and Trace Elements of Sulfide Ore Mineralization and their Host Rocks

This article presents and interprets new geochemical data from the Gallala sulfide mineralization, situated in the Choman District of the Kurdistan Region of Iraq close to the Iraq and Iranian border. The host rocks belong to the Walash-Naopurdan Group, which developed in the Paleocene-Eocene age in the Zagros Suture Zone. The ore mineral assemblage of the Gallala area consists of pyrite, chalcopyrite, sphalerite, and magnetite. The mineral chemistry and geochemical analysis indicate that there is a significant variation in concentrations of pyrite, chalcopyrite, sphalerite, and magnetite from the Gallala mineralization. The trace element characteristics of the sulfide mineralization and their host rocks indicate that the ore-forming materials were derived from hydrothermal fluids being interacted with the igneous rocks. The trace element signatures and REE distributions of the studied samples, tectonically lead to suggest island-arc and back-arc environments in the Gallala area. Additionally, the REE patterns of the Gallala sulfides indicate the ore-forming fluids are related to arc-related hydrothermal systems. The integration of geochemical features along with the chemistry of ore mineralization such as the Selenium/Sulfur ratio of pyrite, Co/Ni ratios from both pyrite and chalcopyrite, the Zn/Cd values from the sphalerite, and the petrogenetic discriminate diagrams of magnetite reveal that the genesis of the sulfide mineralization can be attributed to volcanogenic to hydrothermal ore-formations with high to medium temperatures origin.

In Ukrainian

The work is devoted to the investigation of the morphology and adsorption properties of powder composites based on biogenic hydroxyapatite modified by magnetite (1, 5, 25, 50 wt. %) of various types (synthesis methods) and chitosan. The morphology of the powders evaluated using SEM micrographs and AMIS software is characterized by a uniform distribution of particles size and shape. It was established that the use of magnetite synthesized by chemical precipitation in the amount of 1-5% allows to obtain composite materials with a particle size in a narrower size range. Analysis of the kinetics of adsorption-desorption processes showed that the adsorption of water vapor is directly related to the ratio of hydroxyapatite and magnetite, increasing with increasing magnetite content. In addition, it is shown that the adsorption process for composites modified by magnetite obtained by the chemical precipitation method proceeds uniformly, while for composites containing magnetite obtained by the thermal decomposition method, three consecutive stages of the adsorption process are characteristic: rapid linear increase in mass, gradual inhibition of the adsorption process and stabilization of the mass of the material. The evaluation of the increase in mass also indicates a connection with the ratio of hydroxyapatite and magnetite, increasing with increasing magnetite content, which confirms the presence of physicochemical processes of interaction of gas molecules with the active centers of the molecules of the studied materials. DTGA also shows that the type of magnetite in an amount of more than 25% significantly affects the mass loss of composites during heat treatment up to 1000 °C, which is related to the initial characteristics of the magnetite used. The presented results in combination with previously obtained physicomechanical and biochemical properties testify to the prospects of biogenic hydroxyapatite/magnetite/chitosan composite materials for medicine.

An Evaluation of Cesium Removal from Simulated Radioactive Contaminated Soil with a Magnetized Zeolite Derived from Anthracite

The magnetized zeolite with an optimized conversion rate of 53% can be readily synthesized from industrial anthracite using a water-based method. The highly porous structure of ferromagnetism zeolite demonstrates robust magnetic properties with a magnetite content of 12–15%, satisfying adsorbent separation and recycling through magnetic cylinder rotating and vibrating separation. A cesium adsorption and removal efficiency as high as 99.92% with a corresponding adsorbent recovery ratio of up to 96.36% can be achieved for the simulated cesium-contaminated soil with a water content of 20% and a cesium content of 1% with an adsorbent-to-contaminated soil ratio of 1:2. Adsorption and magnetic separation technology with magnetized zeolite synthesized from anthracite exhibited a high cesium removal rate and zeolite recovery ratio, demonstrating promising application potential in treating radioactive waste soils and robust and economically viable engineering feasibility.

Influence of the material composition of the original ore on the quality of the iron ore concentrate.

In recent years, improvement of blast-furnace process efficiency is largely associated with an increase in the iron content in iron ore concentrates – the feedstock for agglomeration. The study of the material composition of ores, their features makes it possible to adjust the scheme of preparation of raw materials and determine the optimal content of iron in the concentrate for further processing. When studying the material composition, it was found that the sample of iron ore is represented by ferruginous quartzites of the silicate-magnetite type in combination with magnetite. In the original ore sample, magnetite dominates among ore minerals, and quartz and amphiboles dominate among rock-forming minerals. The coarseness and shape of the isolation of magnetite in all varieties of rocks are generally favorable for enrichment; the mineral is characterized by clear rectilinear and slightly sinuous contours, which contributes to its selective isolation. It should be noted that the magnetite content remains constant as the coarseness of the sample material decreases. Automated mineralogical analysis established that 87.36% of iron is associated with magnetite (with fluctuations in size classes from 86.23 to 91.37%); the rest of the iron is associated with rock-forming minerals. The theoretical content of magnetite in iron ore concentrate, achievable by enriching the original ore of the studied sample, according to automated mineralogical analysis, will be 95.83%, which, in turn, will provide the maximum possible iron content in magnetite concentrate of 68.57%. The existing technology of mining and enrich-ment using 4 types of ores from the Stoilenskoye deposit, with a planned increase in iron to 70%, will result to fluctua-tions of this component in the concentrate from 68.0 to 70.0%.

Copper-Bearing Magnetite and Delafossite in Copper Smelter Slags

The cooling paths and kinetics in the system Cu-Fe-O are investigated by the empirical micro- and nanoscale analysis of slags from the flash furnace smelter at Olympic Dam, South Australia. We aim to constrain the exsolution mechanism of delafossite (Cu1+Fe3+O2) from a spinel solid solution (magnetite, Fe3O4) and understand why cuprospinel (CuFe2O4) is never observed, even though, as a species isostructural with magnetite, it might be expected to form. Flash furnace slags produced in the direct-to-blister copper smelter at Olympic Dam contain four Cu-bearing phases: Cu-bearing magnetite, delafossite, metallic copper, and cuprite. Delafossite coexists with magnetite as rims and lamellar exsolutions, as well as bladed aggregates, associated with cuprite within Si-rich glass. The empirical compositions of magnetite and rim delafossite are (Fe2+6.89Cu2+0.86Co0.13Mg0.15Si0.02)8.05 (Fe3+15.52Al0.41Ti0.01Cr0.01)15.95O32, and (Cu1+0.993Co0.002Mg0.002)0.997(Fe3+0.957Al0.027Ti0.005Si0.004)0.993O2, respectively. The measured Cu content of magnetite represents a combination of a solid solution (~6 mol.% cuprospinel endmember) and exsolved delafossite lamellae. Atomic-resolution high-angle annular dark field scanning transmission electron microscope (HAADF STEM) imaging shows epitaxial relationships between delafossite lamellae and host magnetite. Defects promoting the formation of copper nanoparticles towards the lamellae margins suggest rapid kinetics. Dynamic crystallization under locally induced stress in a supercooled system (glass) is recognized from misorientation lamellae in delafossite formed outside magnetite grains. The observations are concordant with crystallization during the cooling of molten slag from 1300 °C to <1080 °C. Melt separation through an immiscibility gap below the solvus in the system Cu-Fe-O is invoked to form the two distinct delafossite associations: (i) melt-1 from which magnetite + delafossite form; and (ii) melt-2 from which delafossite + cuprite form. Such a path also corroborates the published data explaining the lack of cuprospinel as a discrete phase in the slag. Delafossite rims form on magnetite at a peritectic temperature of ~1150 °C via a reaction between the magnetite and copper incorporated in the oxide/Si-rich melt. The confirmation of such a reaction is supported by the observed misfit orientation (~10°) between the rim delafossite and magnetite. HAADF STEM imaging represents a hitherto underutilized tool for understanding pyrometallurgical processes, and offers a direct visualization of phase relationships at the smallest scale that can complement both experimental approaches and theoretical studies based on thermodynamic modelling.

Effects of Magnetite (Fe3O4) as an Electrical Conductor of Direct Interspecies Electron Transfer on Methane Production from Food Wastewater in a Plug Flow Reactor

This study was conducted in order to examine the impact of magnetite (Fe3O4), a conductive material capable of promoting direct interspecies electron transfer (DIET) among microorganisms, on the efficiency of anaerobic digestion in a plug flow reactor (PFR) using food wastewater (FW) as the substrate. The effects of recovering and replenishing magnetite discharged along with the digestate during continuous operation of the PFR were also evaluated. A PFR with a total volume of 17 L was utilized as the reactor for anaerobic digestion. The inoculum was obtained from Icheon Biogas Research Facility, which operated with a mixture of pig slurry and FW in a 7:3 (w/w) ratio. FW was used as the substrate (volatile solids (VS) content of 85,865 mg-VS/L). The PFR was set for operation at 39 °C, and after a stabilization period of approximately 82 days, the hydraulic retention time (HRT) was set at 40 days. The study was conducted in three stages: stage 1 (83~122 days), stage 2 (123~162 days), and stage 3 (163~202 days). For the maintenance of an organic loading rate of 2.12 kg-VS/m3/d, 0.3 L/d of substrate was added every 24 h, and analysis of an equal amount of discharged digestate was performed. The experimental treatments included a control without the addition of magnetite after the stabilization period, treatment (T1) with addition of magnetite (20 mM in digestate) and subsequent recovery and replenishment of magnetite on the discharge of digestate, and treatment (T2) with addition of magnetite (20 mM) without the replenishment of magnetite. Analytical parameters included the characteristics of the discharged digestate (pH, NH4+-N, chemical oxygen demand (CODCr), total volatile fatty acids (TVFAs), and alkalinity), and methane production (Mp). During the period of operation of the PFR after the stabilization period, no significant differences in pH and NH4+-N, based on the recovery and replenishment of magnetite, were observed, and a stably functioning PFR was observed. However, in stage 2, due to the increased degradation of organic matter caused by DIET, the CODCr of T1 and T2 decreased by 9.42% compared with the control. In stage 3, the magnetite content in the reactor in T2 decreased by a maximum of 9.42% compared to T1. In stage 3, the Mp for T2 was similar to that of the control, with a maximum discharge of magnetite of 3.06%, and the Mp decreased by 5.40% compared to T1. Regarding the ratio of methanogens in the community, the results of an analysis of the digestate from stage 3 showed an increase in the community of acetotrophic methanogens, specifically Methanosarcina. The findings of this study confirm that DIET was effectively promoted by maintaining the concentration of 20 mM magnetite in the PFR while using FW as a substrate.

Sources of aeolian magnetite at a remote site in Japan: Dominantly Asian desert dust or anthropogenic emissions?

Asian dust (AD) profoundly impacts human health and the environment, and the soluble Fe in AD is essential for nutrient supply to the ocean and atmospheric chemistry. To accurately assess the impacts of AD, it must be separated from other natural and anthropogenic sources in the total aerosol loading. In this study, coarse aerosol samples (Dp > 2.5 μm) collected in Noto, a remote coastal area in Japan, were analyzed through an environmental magnetic analysis. A comparison of the metal content and Pb isotopic ratios revealed that the magnetization of aerosols, which reflects magnetite content, highly correlated with AD inflow. That is, aerosol magnetite is preferentially concentrated in atmospheric particles during AD events; therefore, AD-affected samples can easily be identified and distinguished from those primarily affected by transboundary air pollution by using magnetic measurements. Based on the magnetization intensity of an AD reference material (CJ-2), the AD loading for ambient samples was estimated to be 5.2–32 μg/m3, similar to that calculated based on the Al mass concentration. Moreover, magnetism is strongly linked with Fe solubility in the ambient samples. This is notable because such information has been obtained previously only through labor-intensive chemical speciation involving sequential extraction. Therefore, magnetism can be used as a new measure of both AD loading and Fe solubility via non-destructive measurements.

Advancing iron ore slimes magnetic separation with functionalized Nanoparticles: Molecular insights from free energy simulations

Magnetic nanoparticles have diverse scientific and technological applications, as their properties can be tuned accordingly. An example is the selective magnetic coating technique for the selective adsorption of these colloidal particles on the surface of iron minerals to improve recovery of fines by magnetic separation. Thus, fundamental physicochemical knowledge of such systems is of paramount importance. Herein, we investigate the adsorption of magnetite nanoparticles on mineral surfaces and the impact of hydrophobic coating on the adsorption process and magnetic separation. We present structural and thermodynamic characterizations from molecular dynamics and free energy simulations to rationalize the differences in association process in both native and coated particle conditions. We demonstrate that hydrophobic coating of both nanoparticle and target iron oxide surfaces is essential for selective adhesion, revealed by ΔG. Also, tuning the degree of surface coverage by oleate leads to better interactions then simply establishing a monolayer coating, because of interdigitation of adsorption layers allowing higher contact area, shorter interparticle distance and less oleate consumption. Magnetic separation experiments of ultrafine iron ore particles under different oleate and colloidal magnetite concentrations validated the molecular level analyses, thus achieving successful experiment–theory nexus based on a sound theoretical background explored beforehand by computational simulations.

Finding fault in a shear zone: a magnetic and drill core study in the Valentine Lake Property, Newfoundland, Canada

The Valentine Lake Property in southwestern Newfoundland has five known gold deposits over a distance of 20 km along a northeast to southwest trend and is expected to be the future site for the largest gold mine in Atlantic Canada. The property contains structurally controlled orogenic-type quartz-tourmaline-pyrite veins, which are gold-bearing, occurring along or proximal to the Valentine Lake Shear Zone. The mineralization is found mostly on the northwest side of the shear zone in intrusive rocks and is rare in the conglomerate on the southeast side. The area has many mafic dykes, which show up well when conducting a magnetic survey due to their magnetite content. These dykes, like the mineralization, occur mainly in the intrusive rocks and trend predominantly subparallel to the shear zone, and so can help indicate structure. To constrain the location of the shear zone (and hence the mineralized region) in an area where an offset was suspected, a detailed magnetic survey was conducted over a 200 m x 300 m grid comprising sixteen lines. With the collected data, residual magnetic intensity maps were created and processed. A region was identified where the pattern of linear magnetic highs weaken and appear to terminate near the suspected offset. In combination with drill core information, this location is interpreted as a fault offset of the shear zone. The loss in magnetic intensity is possibly due to alteration or thinning of the mafic dykes near the fault.

The trace-element compositions of amphibole, magnetite and ilmenite as potential exploration guides to metamorphosed Proterozoic Cu–Zn±Pb±Au±Ag volcanogenic massive sulfide deposits in Colorado, USA

AbstractOrthoamphibole, clinoamphibole and magnetite are common minerals in altered rocks associated spatially with Palaeoproterozoic volcanogenic massive sulfide (VMS) deposits in Colorado, USA and metamorphosed to the amphibolite facies. These altered rocks are dominated by the assemblage orthoamphibole (anthophyllite/gedrite)–cordierite–magnetite±gahnite±sulfides. Magnetite also occurs in granitoids, banded iron formations, quartz garnetite, and in metallic mineralisation consisting of semi-massive pyrite, pyrrhotite, chalcopyrite, and sphalerite with subordinate galena, gahnite and magnetite; amphibole also occurs in amphibolite. The precursor to the anthophyllite/gedrite–cordierite assemblages was probably the assemblage quartz–chlorite formed from hydrothermal ore-bearing fluids (~250° to 400°C) associated with the formation of metallic minerals in the massive sulfide deposits.Element–element variation diagrams for amphibole, magnetite and ilmenite based on LA-ICP-MS data and Principal Component Analysis (PCA) for orthoamphiboles and magnetite show a broad range of compositions which are primarily dependent upon the nature of the host rock associated spatially with the deposits. Although discrimination plots of Al/(Zn+Ca) vs Cu/(Si+Ca) and Sn/Ga vs Al/Co for magnetite do not indicate a VMS origin, the concentration of Al+Mn together with Ti+V and Sn vs Ti support a hydrothermal rather than a magmatic origin for magnetite. Principal Component Analyses also show that magnetite and orthoamphibole in metamorphosed altered rocks and sulfide zones have distinctive eigenvalues that allow them to be used as prospective pathfinders for VMS deposits in Colorado. This, in conjunction with the contents of Zn and Al in magnetite, Zn and Pb in amphibole, ilmenite and magnetite, the Cu content of orthoamphibole and ilmenite, and possibly the Ga and Sn concentrations of magnetite constitute effective exploration vectors.

Magnetic signature and X-ray fluorescence for mapping trace elements in soils originating from basalt and sandstone

The knowledge of the lithological context is necessary to interpret trace elements concentrations in the soil. Soil magnetic signature (χ) and soil X-ray fluorescence (XRF) are promising approaches in the study of the spatial variability of trace elements and the environmental monitoring of soil quality. This research aimed to assess the efficiency of measurements of χ and XRF sensors for spatial characterization of zinc (Zn), manganese (Mn), and copper (Cu) contents in soils of a sandstone-basalt transitional environment, using machine learning modeling. The studied area consisted of the Western Plateau of São Paulo (WPSP), with soils originating from sandstone and basalt. A total of 253 soil samples were collected at a depth of 0.0–0.2 m. The soils were characterized by particle size and chemical analysis: organic matter (OM), cation exchange capacity (CEC), ammonium oxalate-extracted iron (Feo), sodium dithionite-citrate-bicarbonate-extracted iron (Fed), and sulfuric acid-extracted iron (Fet). Hematite (Hm), goethite (Gt), kaolinite (Kt), and gibbsite (Gb) contents were obtained by X-ray diffraction (XRD). Magnetite (Mt) and maghemite (Mh) contents were obtained by soil χ, while trace elements contents were obtained by XRF and predicted by χ. Descriptive analysis, the test of means, and correlation were performed between attributes. Zn, Mn, and Cu contents were predicted using the machine learning algorithm random forest, and the spatial variability was obtained using the ordinary kriging interpolation technique. Landscape dissections influenced iron oxides, which had the highest contents in slightly dissected environments. Trace elements contents were not influenced by landscape dissections, demonstrating that lithological knowledge is necessary to characterize trace elements in soils. The prediction models developed through the machine learning algorithm random forest showed that χ can be used to characterize trace elements. The similar spatial pattern of trace elements obtained by XRF and χ measurements confirm the applicability of these sensors for mapping it under lithological and landscape transition, aiming for sustainable strategic planning of land use and occupation.

Cytotoxic effect of polyvinyl alcohol-magnetite composite

Polymeric hydrogel is a promising candidate for drug delivery applications due to its ability to encapsulate and release drugs. Incorporating magnetic particles enables controlled and specific release, providing sustained and targeted delivery. This study aimed to assess the cytotoxicity of the magnetite-polyvinyl alcohol (MPVA) hydrogel, specifically its magnetite content, using 3T3 fibroblast cells. The findings indicate that the MPVA hydrogel with magnetite nanoparticles was compatible with the cells and did not induce cell death. Incorporating magnetite nanoparticles into the PVA hydrogel improved its thermal stability and degradation temperature, disrupting the chain order, decreasing melting behavior, and fractional crystallinity of the hydrogel. The MPVA hydrogel demonstrated a higher gel fraction and crosslink density compared to the PVA hydrogel due to the presence of magnetite nanoparticles. The interaction between PVA and magnetite nanoparticles occurred through non-covalent forces, allowing for reversible interactions and dispersion of the nanoparticles within the PVA matrix. Although the cytotoxicity of the MPVA gel was similar to that of the PVA gel, the viability of fibroblast cells within the MPVA gel varied depending on the concentration. The MPVA hydrogel exhibited stronger attachment and induced irregular changes on the cell surface compared to the PVA hydrogel. Furthermore, the MPVA gel displayed paramagnetic behavior and controllable magnetization, as demonstrated by the hysteresis loop. These magnetic properties make the MPVA gel suitable for potential biomedical applications, including drug delivery, tissue engineering, and magnetic resonance imaging (MRI) contrast agents.

A detailed magnetic characterization of combustion products from various metamorphic grade coals

The magnetic properties of combustion products from various metamorphic grade coals including lignite, flame coal, gas coal, fat coal, baking coal and lean coal and anthracite coal, were analyzed. This study was carried out by means of basic magnetic parameters, thermomagnetic and hysteresis measurements. The mass magnetic susceptibility (χ) values ranged from 327 × 10−8 m3/kg to 1722 × 10−8 m3/kg, with an average value of 892 × 10−8 m3/kg, demonstrating a considerable amount of ferrimagnetic minerals in these burned coal samples. The lower χ and SIRM values for the burned lignite were probably due to the lower content of magnetite. A characteristic feature of combustion products was their high values of frequency dependent susceptibility (χfd%), indicating the presence of a large amount of superparamagnetic grains of ferrimagnetic minerals within the combustion products. Thermomagnetic analyses of various combustion products showed the dominant role of magnetite-like phase. Moreover, a significant amount of hematite was also only identified in the combustion product from Flame coal. While the combustion products from Flame coal and Fat coal were characterized by a relatively narrow loop, characteristic of magnetically soft ferrimagnetic minerals, other combustion products including lignite, gas coal, baking coal, lean coal and anthracite coal displayed wasp-waisted loops, indicating the presence of two or more coercivity fractions.