Search Results (1,987)

This study investigates magnetic harvesting of Chlorella vulgaris cultivated under saline and wastewater conditions using Fe₃O₄ and polyethylene-glycol-coated Fe₃O₄ (Fe₃O₄@PEG) nanoparticles synthesized by ultrasound-assisted coprecipitation. TEM showed agglomerated, quasi-spherical particles with mean diameters of 13 ± 1 nm (Fe₃O₄) and 15 ± 1 nm (Fe₃O₄@PEG). FTIR confirmed the Fe–O vibrational bands of magnetite and the characteristic PEG vibrations in the coated sample. VSM measurements indicated superparamagnetic behavior, with saturation magnetizations of 72.74 emu/g for Fe₃O₄ and 32.25 emu/g for Fe₃O₄@PEG. SEM–EDX of native and functionalized cells verified nanoparticle attachment on the algal surface. Magnetic separation experiments (OD684) showed a decrease in supernatant absorbance with increasing nanoparticle dose, consistent with biomass removal; the PEG-coated system showed a lower apparent biomass concentration after functionalization. Full article

Magnetic nanocomposite sorbents are increasingly explored for the remediation of metal-contaminated waters; however, high abiotic removal efficiency may not always translate into biological safety. The present study evaluated the single and combined effects of dissolved cobalt (II) ions and magnetite–chitosan nanocomposites (MCN) in zebrafish (Danio rerio) embryos and larvae. MCN (30 wt.% Fe₃O₄) were synthesized via co-precipitation and crosslinking and physiochemically characterized. Adsorption experiments conducted in fish incubation medium demonstrated the efficacy of divalent Co removal and were well described by the Langmuir isotherm model, with a maximum experimental capacity of 20.08 mg g⁻¹. The biological endpoints encompassed survival, hatching, heart rate, locomotor behavior, and oxidative stress biomarkers in early-stage zebrafish. The presence of cobalt (II) was found to result in a reduced hatching success rate, the induction of persistent bradycardia, and the occurrence of oxidative stress, as evidenced by a decline in SOD activity and an increase in H₂O₂ and MDA levels. The study found that MCN alone did not lead to mortality or increase peroxide levels or lipid peroxidation, although a modest decrease in SOD activity was observed. In contrast, combined exposure to cobalt and MCN resulted in significant delayed mortality (>85% at 96 h) and early neuromotor impairment. These findings indicate that high abiotic sorption efficiency alone does not guarantee reduced biological toxicity when nanomaterial–metal interactions occur. Consequently, safety assessments of remediation nanomaterials should explicitly consider nanomaterial–metal interactions and developmental stage-specific biological responses. Full article

Neoproterozoic iron formations (NIFs), deposited during Cryogenian glaciation events, are critical for understanding early Earth oxidation events and the evolution of glacial–interglacial environments. Apatite, a common accessory mineral in iron formations, holds significant implications for sedimentary environments and diagenetic processes, but these aspects remain underexplored. This study focuses on the Hengyang NIF in the Nanhua Basin, South China. Using whole-rock geochemistry and major and trace element analysis of apatite, we investigate the environmental significance of apatite and associated diagenetic processes. Our results show that the Hengyang NIF are formed through the mixing of low-temperature hydrothermal fluids, seawater, and terrigenous detrital materials, with hydrothermal contributions increasing progressively from the bottom to the top of the iron formation layers. Whole-rock geochemical proxies indicate that the depositional water column evolved from relatively oxidizing to weakly oxidizing conditions. The study further demonstrates that the rare earth element patterns in apatite, characterized by middle rare earth element enrichment, are primarily controlled by porewater chemistry during diagenesis. In contrast, Ce anomalies and the V/Cr and V/(V + Ni) ratios in apatite, which are strongly influenced by fluid–rock interactions and magnetite recrystallization, no longer reliably reflect the primary depositional environment. The Th/U ratio in apatite, due to its geochemical stability, aligns with whole-rock trends and serves as a more reliable redox proxy. Based on these findings, we propose a three-stage depositional-diagenetic model: the early and late stages are characterized by high-energy, rapid sedimentation with minimal diagenetic modification, while the middle stage is dominated by low-energy, stagnant conditions with slow sedimentation rates, leading to prolonged diagenesis and significant decoupling of mineral geochemical signatures. This study emphasizes the need to distinguish between sedimentary and diagenetic signals when using mineral geochemical proxies to reconstruct paleoenvironments and provides new insights into the genesis of Neoproterozoic iron formations. Full article

This study investigated the biosynthesis of magnetite nanoparticles mediated by chia mucilage (CM-Fe₃O₄ NPs) and their application in the co-encapsulation of Lactobacillus rhamnosus GG (LGG) using spray drying. CM-Fe₃O₄ NPs were synthesized by combining CM extract with iron salts, in which hydroxyl and carbonyl groups of CM acted as natural ligands for Fe²⁺/Fe³⁺ ions. A response surface design was applied to optimize synthesis parameters, focusing on size distribution and zeta potential, and confirming the influence of pH on colloidal stability. Characterization by FE-SEM, DLS, XRD, UV-Vis, and FTIR revealed spherical particles with an inorganic core (50–300 nm) and a hydrated organic coating (600–900 nm), consistent with a spinel structure functionalized by CM. Spray-drying encapsulation tests showed that incorporating CM-Fe₃O₄ NPs did not compromise bacterial viability, maintaining optimal moisture content and survival. Growth curves and confocal microscopy corroborated the physiological compatibility of the nanoparticles, with no alterations in LGG morphology or growth dynamics. Under simulated gastrointestinal conditions, co-encapsulated microcapsules exhibited slightly improved survival in the gastric phase and significantly greater viability in the initial intestinal phase. These results suggest that CM-Fe₃O₄ NPs modulate matrix degradation and promote controlled release, ensuring therapeutic concentrations of LGG in the intestine. Overall, the CM-Fe₃O₄ nanocomposite system integrates the protective properties of biopolymers with the functional advantages of iron nanoparticles, offering dual functionality: probiotic stabilization and potential iron supplementation. This innovative, food-grade approach supports the development of next-generation functional foods with combined therapeutic and nutritional benefits. Full article

Variscan two-mica granites are widespread in the Trás-os-Montes region (NE Portugal), yet their emplacement ages, petrogenesis, and relationship with Variscan deformation phases remain poorly constrained. This study integrates U–Pb zircon geochronology, whole-rock geochemistry, and oxygen isotope data to characterise four peraluminous two-mica granites in the Trás-os-Montes area (Fornos, Carviçais, Fonte Santa, and Bruçó) and to refine their tectonomagmatic context within the Central Iberian Zone. All granites are S-type, ilmenite-series, and derived from reduced magmas, as indicated by their strongly peraluminous compositions, mineral assemblages (muscovite ± biotite), absence of magnetite and presence of ilmenite, and high δ¹⁸O values (>11‰), consistent with partial melting of metasedimentary crust. U–Pb ages reveal two distinct magmatic pulses: an older event at ~340 Ma (Fornos and Fonte Santa granites), predating the onset of C3 deformation and likely associated with late C1 crustal thickening to early C2 tectonics, and a younger pulse at ~320–318 Ma (Carviçais and Bruçó granites). These magmatic pulses are linked to contrasting structural controls, with the older granites emplaced within regional-scale antiforms and the younger intrusions localised along structures related to C3 deformation. Together, these results document two discrete crustal melting events separated by ~20 Ma and record a progressive shift from fold-controlled to strike-slip-dominated granite emplacement during Variscan orogenic evolution. Moreover, the study highlights that tungsten mineralisation is preferentially associated with reduced, crust-derived granites emplaced during specific tectonic regimes, providing new constraints for metallogenic models in NW Iberia. Full article

Vanadium (V) is a strategically important metal commonly recovered from titaniferous magnetite ores. Its principal application is in steel production, where it enhances mechanical properties, while smaller quantities are utilized in chemical processing, catalysis, and emerging energy storage technologies. It is expected that the demand for vanadium in the steel industry will increase by a compound annual growth rate of approximately 2.7% by 2029, and demand in energy storage will increase by an additional 6%. The growing demand for V has triggered global concerns regarding the supply risks of this critical metal. Industrial recovery of vanadium from magnetite deposits is carried out either through dedicated primary vanadium extraction routes or integrated processes that co-produce vanadium alongside steel. The latter accounted for approximately 73% of global vanadium output in 2021. These co-production operations generate significant volumes of by-product slag, often referred to as titaniferous slag, which can still contain notable concentrations of vanadium. In this study, a modified primary vanadium extraction route is proposed to recover V from such slag, using material containing approximately 0.9% V₂O₅ sourced from the former Evraz Highveld Steel and Vanadium Corporation in South Africa as a representative case. The work focuses on assessing the economic feasibility of the proposed process through a Discounted Cash Flow (DCF) analysis. Key financial metrics including net present value (NPV), internal rate of return (IRR), and payback period were calculated to evaluate viability and to identify process stages requiring further optimization. Full article

The advancement of green and low-carbon transition in the steel industry has increased the demand for high-quality direct reduced iron (DRI) as a premium feedstock for electric arc furnace steelmaking. This imposes stricter quality requirements for fired pellets utilized in gas-based shaft furnace processes. To address the poor low-temperature reduction degradation (LTD) of fired pellets produced from a single high-grade magnetite concentrate during gas-based direct reduction. This study investigates the effects of blending hematite concentrates into a magnetite concentrate base (with additions of 0, 20 wt.%, 30 wt.%, and 40 wt.%) on the characteristics of the mixed concentrates, green ball properties, firing performance, and the metallurgical performance of the resulting fired pellets under conditions simulating an HYL shaft furnace. The results indicate that the incorporation of hematite concentrate optimizes the overall particle size distribution and green ball properties. As the hematite proportion increases, the optimal preheating temperature for green balls rises, while the required roasting temperature decreases. The most significant reduction in roasting temperature, from 1225 °C to 1175 °C, is achieved with a 20 wt.% hematite addition. Regarding metallurgical properties, the addition of hematite has a minor effect on the reducibility index (RI) but substantially improves the reduction swelling index (RSI). A notable decrease in the RSI is observed at addition levels of 30% and above. Critically, the LTD is significantly enhanced. The optimal improvement is attained with a 20 wt.% hematite blend, resulting in a- LTD_{+6.3 mm} fraction of 97.48 wt.%, a- LTD_{−3.2 mm} fraction of only 2.18 wt.%, and a whole pellet ratio of 88.01% after reduction. Considering the comprehensive performance, a blend of hematite concentrate between 20 wt.% and 30 wt.% yields fired pellets with superior characteristics, meeting the production requirements for gas-based shaft furnace direct reduction processes. This study provides an effective technological pathway for producing high-performance DRI-grade pellets from high-grade magnetite concentrates, contributing to the green and low-carbon transformation of the iron and steel industry. Full article

The Yechangping super-large porphyry–skarn deposit is a key component of the East Qinling molybdenum metallogenic belt, central China. Magnetite is widely developed across all mineralization stages of this deposit, yet its systematic geochemical evolution and prospecting significance remain poorly constrained. This study presents in situ major- and trace-element analyses of magnetite via electron probe microanalysis (EPMA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and elemental mapping, to unravel the ore-forming hydrothermal evolution and establish reliable prospecting indicators. Four magnetite generations are identified based on petrography and paragenetic relationships: late skarn stage (Mt1), oxide stage (Mt2 and Mt3), and polymetallic sulfide stage (Mt4). Magnetite has total iron contents (TFeO, total Fe calculated as FeO) of 82.72–95.46 wt.% (values above the 93 wt.% stoichiometric limit of pure magnetite stem from minor oxidation), with dominant isovalent Fe³⁺ and Al³⁺ lattice substitution supported by a significant negative Fe–Al correlation. Systematic stage-dependent geochemical variations are observed: Mt1 has the highest Ti (mostly >1500 ppm), V and Cr, while Mt2–Mt4 show progressive Ti depletion (mostly <100 ppm), recording continuous cooling of the hydro-thermal system. V and Cr contents decrease markedly from Mt1 to Mt3, with secondary enrichment in Mt4; Mo concentrations peak in Mt2 (average 5.06 ppm), coupled with elevated chalcophile metalloid Te, As, Pb and Bi. Elemental mapping results show that K occurs as discrete hotspots, which may be mainly derived from feldspar microinclusions, rather than lattice substitution in magnetite. These geochemical fingerprints record a transition from high-temperature magmatic–hydrothermal fluids to late contact-metasomatic fluids, with evolving fluid–rock interaction and oxygen fugacity. Our results demonstrate that magnetite chemistry is a reliable tool for discriminating mineralization stages and vectoring prospecting targets in porphyry–skarn Mo–W systems. Full article

Fenton-based processes are widely used advanced oxidation methods that are known for degrading persistent pollutants. However, these techniques often generate significant amounts of iron-containing sludge, which poses environmental disposal challenges due to its complex composition. Furthermore, the sludge produced by the Fenton process contains a high content of Fe(III) compounds, which can serve as an iron source to stimulate dissimilatory iron reduction (DIR), enhancing the performance of anaerobic digestion. Based on the characterization results from a previous study, this work investigated the use of the ferrous precipitate generated by the electrochemical peroxidation process applied to tannery wastewater treatment as an additive to enhance volatile fatty acids (VFAs) production during dark fermentation. The performance of ferrous precipitate (R-Fe₃O₄) was compared to that of conventional magnetite (Fe₃O₄) during dark fermentation under high organic loading conditions, emphasizing their potential to enhance hydrolysis efficiency and VFAs production yields, while promoting sustainable resource recovery and reuse within a circular bioeconomy framework. The results showed that the addition of both Fe₃O₄ and R-Fe₃O₄ significantly increased the VFAs yields, with a predominance of long-chain fatty acids. The presence of CaCO₃ in the ferrous precipitate contributed to maintaining a stable pH environment, supporting microbial activity and enhancing the hydrolysis of soluble compounds. Moreover, the availability of essential micronutrients within the ferrous precipitate favored greater microbial diversity. Consequently, the addition of R-Fe₃O₄ promoted VFAs production, even at higher organic loading rates, suggesting a promising application of Fenton-based by-products as functional additives to improve the economic and environmental performance of the dark fermentation process. Full article

The Xinqiao Cu-S polymetallic deposit is located in the Tongling ore concentration area of the Middle-Lower Yangtze River metallogenic belt. The orebodies consist of skarn orebodies and stratiform sulfide orebodies, but the genetic link between them remains controversial. In this study, magnetite was used as a proxy to systematically constrain the hydrothermal evolution from the intrusion to the contact zone and further to the stratiform orebodies. A representative drill hole (E603) was logged, and samples were systematically collected from the Jitou pluton outward to the contact zone. Composite samples from the 8–28 m interval were crushed and prepared as resin mounts for integrated TIMA automated mineralogy, BSE textural observation, and in situ LA-ICP-MS trace element analysis. Five types of magnetite (Mt1 to Mt5) were systematically identified. Mt1 occurs as inclusions within feldspar in the quartz monzodiorite. It exhibits typical magmatic magnetite characteristics and contains grid-like ilmenite exsolution, indicating crystallization during the late magmatic stage. Mt2 is distributed in the interstices of magmatic minerals, commonly showing hematitization and replacement of ilmenite exsolution lamellae by titanite. Its trace element geochemistry displays magmatic–hydrothermal transitional features. Mt3–Mt5 in the skarn and stratiform orebodies are paragenetic with retrograde alteration minerals (e.g., epidote, chlorite, and actinolite) and sulfides, and are characterized by low Ti, Al, and V contents and high Mg, Mn, and Sn contents, indicating a hydrothermal origin. From Mt3 to Mt5, (Ti + V) and (Al + Mn) decrease, while Zn and Mn increase, accompanied by a decrease in the (Si + Al)/(Mg + Mn) ratio. This reflects a trend of decreasing fluid temperature and progressively enhanced wall-rock buffering. The Mg-in-magnetite geothermometer yields relatively consistent results for Mt1–Mt3, but anomalously high temperatures for Mt4–Mt5. This suggests that the elevated Mg activity in the fluid, caused by reaction with carbonate wall rocks, can significantly influence the calculated temperatures. Therefore, this geothermometer should be used cautiously for magnetite in the outer skarn zone and interpreted in combination with other temperature constraints. The textures, paragenetic mineral assemblages, and trace element characteristics of magnetite collectively reveal a continuous mineralization process linking the skarn and stratiform orebodies at Xinqiao, providing robust mineralogical and geochemical evidence for the contribution of Yanshanian magmatic–hydrothermal activity to the stratiform mineralization. Full article

Many advances in enhanced oil recovery (EOR) take advantage of the unique properties of nanomaterials to improve characterization of formation properties, achieve conformance control during flood operations, and extend the controlled release time of polymers. Magnetite nanoparticles (nMag) have been employed in these processes due to their low cost, low toxicity, and ability to be engineered to meet desired needs, especially with the application of a magnetic field. Similarly, silica dioxide (SiO₂) and aluminum oxide (Al₂O₃) nanoparticles have been evaluated for the delivery of scale and asphaltene inhibitors. However, the injection of nanoparticles into porous media comes with the risk of formation damage due to particle deposition, which can lead to increased injection pressures and reductions in permeability. The goal of this study was to develop a method to evaluate and assess nanoparticle formulations for their potential to cause formation damage. A screening apparatus was constructed to hold small sandstone discs (~2 mm) or cores (~2.5 cm) for rapid testing with minimal material use and the capability to be used with either aqueous brine solutions or non-polar solvents as the mobile phase. Image analysis of the disc and pressure measurements demonstrated increasing deposition of nMag and face-caking when the salinity was increased from 500 mg/L NaCl (8.56 mM) to API brine (2.0 M). Similarly, when the injected concentration of silica nanoparticles in 500 mg/L NaCl was increased from 1 to 10 wt%, the back pressure increased by 55 psi, and face-caking was observed. The screening test results were consistent with traditional core-flood tests and was able to be modified to accommodate organic liquid mobile phases. The screening test results closely matched nanoparticle transport and retention measured in sandstone cores, confirming the ability of the system to rapidly screen nanoparticle formulations for potential formation damage. Full article

Biopolymers such as chitosan are considered important candidates for water purification due to their non-toxicity, biodegradability, natural origin, biocompatibility, and potential for modification to provide additional capabilities, such as incorporating nanomaterials for magnetism to enable rapid separation or adding functional groups to enhance selectivity towards target adsorbates. This study investigated adsorption of Co (II), traced by Co-60 radionuclide, systematically evaluated in natural aquatic matrices selected according to water body type: seawater (Baltic Sea) and freshwater systems further distinguished as lentic (Lake Balsys) and lotic (Neris River) environments, using synthesized magnetite–chitosan nanocomposites (MCNs) with varying loadings of Fe₃O₄ (10–30 wt. %) nanoparticles providing different levels of magnetization. Comprehensive characterization (TEM, FTIR, AFM, XRD, and Mössbauer spectroscopy) confirmed successful integration of magnetite nanoparticles within the chitosan matrix and reproducible structural properties. An optimal magnetization of 11 emu/g was achieved at 20 wt. % Fe₃O₄, enabling rapid magnetic separation within <1 min without compromising sorption capacity. Adsorption isotherm models were applied to investigate the adsorption parameters, and sorption kinetics were studied, yielding a maximum adsorption capacity of 14.93 mg/g for MCN-10 in seawater and 11.95 mg/g for MCN-20 in freshwater with observed equilibrium within 120 min. These promising results indicate that the MCN is a suitable nanocomposite for the removal of Co (II) ions and the Co-60 radionuclide from aquatic media. Full article

Magnetic nanoparticles represent the next-generation drug delivery systems, enabling drug targeting to specific organs without adverse effects on the body and with a controlled release rate. Their strengths are represented by biocompatibility, low cost, and easy drug loading; some drawbacks are aggregation and poor stability in biological media. In the present work, we synthesized magnetic core–shell structures with a magnetite core coated with layered double hydroxides (LDHs) based on Mg²⁺ or Zn²⁺ and Al³⁺ ions and loaded with meloxicam, a poorly water-soluble anti-inflammatory drug. Several syntheses have been attempted to obtain iron oxides based on the only magnetite phase. The combined use of different characterization techniques allowed us to reveal that the best product, showing the crucial room temperature superparamagnetism and a good level of compositional uniformity, was obtained from co-precipitation in nitrogen flow. The next LDH coating was successful, even if the hybrids showed the occurrence of aggregation. The drug was mainly adsorbed onto the LDH surfaces, as shown by the X-ray diffraction and Infrared Spectroscopy techniques. The loaded meloxicam amount was low, but the subsequent release into simulated body fluid could be prolonged for 4 days. Our study provides a proof of concept about the importance of a thorough characterization of the nanocomposite hybrids and their possible use for tricky drugs, such as those of class II of the Biopharmaceutical Classification System. Full article

Iron oxide particles (magnetite Fe₃O₄, hematite α-Fe₂O₃, and maghemite γ-Fe₂O₃) are prevalent constituents of atmospheric particulate matter (PM) and have gained increasing attention due to potential health implications. This scoping review provides a broad mapping of published in vivo and in vitro studies addressing the biological and toxicological effects of iron oxide particles across particle size fractions (PM10, PM2.5, PM1.0, and nanoscale) and exposure routes, including inhalation, intranasal instillation, and intravenous administration. As a scoping review, no formal risk-of-bias appraisal was conducted; however, studies were selected through predefined eligibility criteria and a structured screening workflow. Iron oxide exposure is consistently associated with oxidative stress and inflammatory responses, while mitochondrial dysfunction, genotoxicity, and neurological effects are frequently reported depending on particle characteristics and exposure context. Among studies with explicit crystalline phase identification, magnetite is most frequently associated with higher biological reactivity, whereas hematite and maghemite display more variable and context-dependent responses. Limited human evidence aligns with experimental findings, identifying magnetite-rich nanoparticles in neural and cardiovascular tissues alongside markers of oxidative and mitochondrial damage. Overall, this scoping review highlights dominant research trends, mechanistic pathways, and key knowledge gaps regarding iron oxide-containing PM, emphasizing the need for integrative approaches linking atmospheric particle characterization with toxicological research. Full article

The usage of magnetic nanoparticles (MNPs), particularly iron oxide-based systems such as magnetite (${\mathrm{Fe}}_3$${\mathrm{O}}_4$) and maghemite ($\gamma$-${\mathrm{Fe}}_2$${\mathrm{O}}_3$), has significantly advanced the field of theranostics. These nanoparticles unite therapeutic and diagnostic capabilities due to their favorable magnetic properties and surface engineering potential. However, the path from synthesis to clinical application poses substantial challenges, including optimization of structure–property–function relationships, biocompatibility issues, and effective surface functionalization. Various synthesis methods, such as co-precipitation and thermal decomposition, aim to achieve specific nanoparticle characteristics, although they encounter obstacles related to scalability and reproducibility. Furthermore, characterizing these systems through structural, microstructural and spectroscopic techniques is vital to determine their functional efficacy and ensure their safe biomedical usage. This review comprehensively examines recent advancements and identifies existing challenges in the clinical translation of MNPs, highlighting the need for refined methods and standardized protocols to effectively exploit their theranostic potential. It outlines future directions, emphasizing the importance of green synthesis and robust characterization frameworks to enhance the integration of MNPs in personalized medicine. Full article