Iron Oxide Research Articles

Colored Radiative Cooling and Flame-Retardant Polyurethane-Based Coatings: Selective Absorption/Reflection in Solar Waveband.

The aesthetic demand has become an imperative challenge to advance the practical and commercial application of daytime radiative cooling technology toward mitigating climate change. Meanwhile, the application of radiative cooling materials usually focuses on the building surface, related tightly to fire safety. Herein, the absorption and reflection spectra of organic and inorganic colorants are first compared in solar waveband, finding that iron oxides have higher reflectivity in NIR region. Second, three kinds of iron oxides-based colorants are selected to combine porous structure and silicon-modified ammonium polyphosphate (Si-APP) to engineer colored polyurethane-based (PU) coating, thus enhancing the reflectivity and flame retardancy. Together with reflectivity of more than 90% in near-infrared waveband and infrared emissivity of ≈91%, average temperature drops of ≈5.7, ≈7.9, and ≈3.8°C are achieved in porous PU/Fe2O3/Si-APP, porous PU/Fe2O3·H2O/Si-APP, and porous PU/Fe3O4·H2O/Si-APP, compared with dense control samples. The catalysis effect of iron oxides in the cross-linking reaction of pyrolysis products and dehydration mechanism of Si-APP enable PU coating to produce an intumescent and protective char residue. Consequently, PU composite coatings demonstrate desirable fire safety. The ingenious choice of colorants effectively minimizes the solar heating effect and trades off the daytime radiative cooling and aesthetic appearance requirement.

Magnetic iron oxide nanogels for combined hyperthermia and drug delivery for cancer treatment.

Hyperthermia and chemotherapy represent potential modalities for cancer treatments. However, hyperthermia can be invasive, while chemotherapy drugs often have severe side effects. Recent clinical investigations have underscored the potential synergistic efficacy of combining hyperthermia with chemotherapy, leading to enhanced cancer cell killing. In this context, magnetic iron oxide nanogels have emerged as promising candidates as they can integrate superparamagnetic iron oxide nanoparticles (IONPs), providing the requisite magnetism for magnetic hyperthermia, with the nanogel scaffold facilitating smart drug delivery. This review provides an overview of the synthetic methodologies employed in fabricating magnetic nanogels. Key properties and designs of these nanogels are discussed and challenges for their translation to the clinic and the market are summarised.

Confining Conversion Chemistry in Intercalation Host for Aqueous Batteries.

Conversion-type anode materials with high theoretical capacities play a pivotal role in developing future aqueous rechargeable batteries (ARBs). However, their sustainable applications have long been impeded by the poor cycling stability and sluggish redox kinetics. Here we show that confining conversion chemistry in intercalation host could overcome the above challenges. Using sodium titanates as a model intercalation host, an integrated layered anode material of iron oxide hydroxide-pillared titanate (FeNTO) is demonstrated. The conversion reaction is spatially and kinetically confined within sub-nano interlayer, enabling superlow redox polarization (ca. 4-6 times reduced), ultralong lifespan (up to 8700 cycles) and excellent rate performance. Notably, the charge compensation of interlayer via universal cation intercalation into host endows FeNTO with the capability of operating well in a broad range of aqueous electrolytes (Li+, Na+, K+, Mg2+, Ca2+, etc.). We further demonstrate the large-scale synthesis of FeNTO thin film and powder, and rational design of quasi-solid-state high-voltage ARB pouch cells powering wearable electronics against extreme mechanical abuse. This work demonstrates a powerful confinement means to access disruptive electrode materials for next-generation energy devices.

Impact of additives on syntrophic propionate and acetate enrichments under high-ammonia conditions

High ammonia concentrations in anaerobic degradation systems cause volatile fatty acid accumulation and reduced methane yield, which often derive from restricted activity of syntrophic acid-oxidising bacteria and hydrogenotrophic methanogens. Inclusion of additives that facilitate the electron transfer or increase cell proximity of syntrophic species by flocculation can be a suitable strategy to counteract these problems, but its actual impact on syntrophic interactions has yet to be determined. In this study, microbial cultivation and molecular and microscopic analysis were performed to evaluate the impact of conductive (graphene, iron oxide) and non-conductive (zeolite) additives on the degradation rate of acetate and propionate to methane by highly enriched ammonia-tolerant syntrophic cultures derived from a biogas process. All additives had a low impact on the lag phase but resulted in a higher rate of acetate (except graphene) and propionate degradation. The syntrophic bacteria ‘Candidatus Syntrophopropionicum ammoniitolerans’, Syntrophaceticus schinkii and a novel hydrogenotrophic methanogen were found in higher relative abundance and higher gene copy numbers in flocculating communities than in planktonic communities in the cultures, indicating benefits to syntrophs of living in close proximity to their cooperating partner. Microscopy and element analysis showed precipitation of phosphates and biofilm formation in all batches except on the graphene batches, possibly enhancing the rate of acetate and propionate degradation. Overall, the concordance of responses observed in both acetate- and propionate-fed cultures highlight the suitability of the addition of iron oxide or zeolites to enhance acid conversion to methane in high-ammonia biogas processes.Key points• All additives promoted acetate (except graphene) and propionate degradation.• A preference for floc formation by ammonia-tolerant syntrophs was revealed.• Microbes colonised the surfaces of iron oxide and zeolite, but not graphene.Graphical

Pulsed MPI Relaxometry of Brownian and Néel Field-Dependent Relaxation in Superparamagnetic Magnetite Nanoparticles Confirm Theory and Simulations.

Superparamagnetic iron oxide nanoparticles (SPIOs) are used as tracers in Magnetic Particle Imaging (MPI). It is crucial to understand the magnetic properties of SPIOs for optimizing MPI imaging contrast, resolution, and sensitivity. Brownian and Néel relaxation theory developed in the early 1950s posits that relaxation times can vary with particle size, shell thickness, medium viscosity, and the applied field strength. Magnetic relaxation can soon provide a unique imaging capability, the ability to distinguish bound from unbound MPI tracers in vivo. Yet experimental validation of these theories has not been completed. In this paper, a novel method of pulsed magnetic field relaxometry is used to directly probe the relaxation behavior of superparamagnetic magnetite nanoparticles over a spectrum of magnetic field amplitudes, providing the first experimental validation of theoretical relaxation models. It is also shown that closed-form approximations generated in the early 1970s accurately match both data and numerical Fokker Planck computational models, which are computationally burdensome. This means researchers can trust these approximations for future modeling. All the findings can be translated to sinusoidal excitations used in conventional MPI scanningtrajectories.

Temporal Optimization in the Synthesis of Multifunctional Nano Agents for Enhanced MRI Contrast, Hyperthermia Therapy, and ROS Generation.

Advanced methodologies, such as hyperthermia and modulation of reactive oxygen species (ROS), exhibit considerable promise in the therapeutic landscape of cancer. These strategies offer a targeted paradigm for combating malignant cells while mitigating damage to healthy tissue. Noteworthy among these approaches is the utilization of superparamagnetic iron oxide nanoparticles, which are renowned for their ability to enhance both hyperthermia and ROS generation specifically within tumor microenvironments. The objective of this investigation is to scrutinize the relationship between the reaction duration and the characteristics of carbon-doped silica core-shell iron oxide nanoparticles (CSIONPs). Specifically, we focus on CSIONP-12, CSIONP-24, and CSIONP-36, synthesized by using varying reaction periods. Through a comprehensive analysis, we primarily evaluate the impact of these formulations on T1 and T2 magnetic resonance imaging (MRI), aiming to elucidate their mechanisms and therapeutic potential in promoting hyperthermia and ROS-mediated cancer therapy. CSIONP-24 emerges as a compelling candidate due to its dual influence on magnetic hyperthermia and ROS generation, suggesting its promise in enhancing cancer treatment outcomes. Furthermore, the findings underscore the exceptional T1-T2 MRI capabilities of this technology, underscoring its versatility and efficacy in the nuanced realm of cancer theranostic.

Integrating remote sensing and geophysical data for mapping potential gold mineralization localities at Abu Marawat area, central Eastern Desert, Egypt

Abu Marawat area in the Central Eastern Desert of Egypt is a very promising mineralization district located in the Golden Triangle area. The current study provides an integrated approach from multisource datasets including; remote sensing, airborne geophysical spectrometry and magnetic data supported by field studies and spectroscopic analyses for delineating potential mineralization localities. Several remote sensing techniques were adopted including; Band Ratios, Relative Band Depth, Mineralogical Indices, Spectral Angle Mapper, and Constrained Energy Minimization. These techniques showed that the alteration mineral assemblage is mainly, kaolinite, sericite, and iron oxides, with less abundant chlorite, epidote, and carbonates. In addition, the radiometry data were processed to map the localities with the highest possibility of potassic alteration abundance by integrating the potassium distribution, K/eTh ratio, and the F-parameter maps. The surface and subsurface linear structural features were also mapped using Digital Elevation Model (DEM) and aeromagnetic data, respectively. The surface linear structures were found exhibiting E-W and NE-SW trends, while, the subsurface structures showed dominant NW–SE trend. All the depicted fault trends match well with the local and regional geological and tectonic setting of the study area suggesting structural control on the mineralization in this area. Integration between the results obtained from both the remote sensing and the geophysical data was conducted by a GIS weighted overlay model. The obtained mineralization potentiality map highlights eight potential localities for mineralization. The accuracy of the adopted methodology was demonstrated through fieldwork and spectral analyses; several alteration indicators were observed, including quartz veins, iron oxides, kaolinite, malachite, montmorillonite, chlorite, talc, and sericite alteration indicator minerals. The adopted remote sensing-geophysical approach showed being very effective for mapping the hydrothermal gold-related alteration zones, and is recommended for other similar investigations.

Magnetic functionalization of brushite microplatelets and rheological analysis of slurries

Natural ceramics such as bone and teeth possess complex microstructures comprising inorganic minerals oriented in various directions, allowing them to perform biological and mechanical functions. Among the various processes developed to mimic natural microstructural arrangement, magnetically assisted slip casting (MASC), a process that locally orients magnetically functionalized ceramic microplatelets suspended in a slurry while the solvent is slowly sucked out, is deemed promising. However, MASC has not yet been applied to bioceramic materials due to the lack of recipes for functionalized bioceramic microplatelets and for slurries. This study therefore explores the magnetic functionalization of synthesized brushite microplatelets with various sizes and their magnetic response. After coating with superparamagnetic iron oxide nanoparticles, brushite microplatelets synthesized at 2 and 22°C exhibited a diameter of 10 μm and an alignment time of less than 12 s. Aqueous slurries with 12 vol% brushite were prepared, and their rheological properties and stabilities were measured. It was found that all slurries exhibited a solid-like nature and low stability, which may be exacerbated by the presence of iron oxide at the surface of brushite. Further approaches to slurry preparation are discussed to guide future development of calcium phosphate-based slurries in view of future microstructured bioceramics and biocomposites produced using MASC.

Innovative thermal management in the presence of ferromagnetic hybrid nanoparticles

In the present work, a simple intelligence-based computation of artificial neural networks with the Levenberg-Marquardt backpropagation algorithm is developed to analyze the new ferromagnetic hybrid nanofluid flow model in the presence of a magnetic dipole within the context of flow over a stretching sheet. A combination of cobalt and iron (III) oxide (Co-Fe2O3) is strategically selected as ferromagnetic hybrid nanoparticles within the base fluid, water. The initial representation of the developed ferromagnetic hybrid nanofluid flow model, which is a system of highly nonlinear partial differential equations, is transformed into a system of nonlinear ordinary differential equations using appropriate similarity transformations. The reference data set of the possible outcomes is obtained from bvp4c for varying the parameters of the ferromagnetic hybrid nanofluid flow model. The estimated solutions of the proposed model are described during the testing, training, and validation phases of the backpropagated neural network. The performance evaluation and comparative study of the algorithm are carried out by regression analysis, error histograms, function fitting graphs, and mean squared error results. The findings of our study analyze the increasing effect of the ferrohydrodynamic interaction parameter β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta$$\\end{document} to enhance the temperature and velocity profiles, while increasing the thermal relaxation parameter α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document} decreases the temperature profile. The performance on MSE was shown for the temperature and velocity profiles of the developed model about 9.1703e−10, 7.1313ee−10, 3.1462e−10, and 4.8747e−10. The accuracy of the artificial neural networks with the Levenberg-Marquardt algorithm method is confirmed through various analyses and comparative results with the reference data. The purpose of this study is to enhance understanding of ferromagnetic hybrid nanofluid flow models using artificial neural networks with the Levenberg-Marquardt algorithm, offering precise analysis of key parameter effects on temperature and velocity profiles. Future studies will provide novel soft computing methods that leverage artificial neural networks to effectively solve problems in fluid mechanics and expand to engineering applications, improving their usefulness in tackling real-world problems.

Chalcopyrite bioleaching efficacy by extremely thermoacidophilic archaea leverages balanced iron and sulfur biooxidation

Factors that contribute to optimal chalcopyrite bioleaching by extremely thermoacidophilic archaea were examined for ten species belonging to the order Sulfolobales from the genera Acidianus (A. brierleyi), Metallosphaera (M. hakonensis, M. sedula, M. prunae), Sulfuracidifex (S. metallicus, S. tepriarius), Sulfolobus (S. acidocaldarius), Saccharlobus (S. solfataricus) and Sulfurisphaera (S. ohwakuensis, S. tokodaii). Only A. brierleyi, M. sedula, S. metallicus, S. tepriarius, S. ohwakuensis, and S. tokodai exhibited significant amounts of bioleaching and were investigated further. At 70–75 °C, Chalcopyrite loadings of 10 g/l were leached for 21 days during which pH, redox potential, planktonic cell density, iron concentrations and sulfate levels were monitored, in addition to copper mobilization. S. ohwakuensis proved to be the most prolific bioleacher. This was attributed to balanced iron and sulfur oxidation, thereby reducing by-product (e.g., jarosites) formation and minimizing surface passivation. Comparative genomics suggest markers for bioleaching potential, but the results here point to the need for experimental verification.

Green synthesis of magnetite iron oxide nanoparticles using Azadirachta indica leaf extract loaded on reduced graphene oxide and degradation of methylene blue

In the current arena, new-generation functional nanomaterials are the key players for smart solutions and applications including environmental decontamination of pollutants. Among the plethora of new-generation nanomaterials, graphene-based nanomaterials and nanocomposites are in the driving seat surpassing their counterparts due to their unique physicochemical characteristics and superior surface chemistry. The purpose of the present research was to synthesize and characterize magnetite iron oxide/reduced graphene oxide nanocomposites (FeNPs/rGO) via a green approach and test its application in the degradation of methylene blue. The modified Hummer's protocol was adopted to synthesize graphene oxide (GO) through a chemical exfoliation approach using a graphitic route. Leaf extract of Azadirachta indica was used as a green reducing agent to reduce GO into reduced graphene oxide (rGO). Then, using the green deposition approach and Azadirachta indica leaf extract, a nanocomposite comprising magnetite iron oxides and reduced graphene oxide i.e., FeNPs/rGO was synthesized. During the synthesis of functionalized FeNPs/rGO, Azadirachta indica leaf extract acted as a reducing, capping, and stabilizing agent. The final synthesized materials were characterized and analyzed using an array of techniques such as scanning electron microscopy (SEM)-energy dispersive X-ray microanalysis (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis, and UV–visible spectrophotometry. The UV–visible spectrum was used to evaluate the optical characteristics and band gap. Using the FT-IR spectrum, functional groupings were identified in the synthesized graphene-based nanomaterials and nanocomposites. The morphology and elemental analysis of nanomaterials and nanocomposites synthesized via the green deposition process were investigated using SEM–EDX. The GO, rGO, FeNPs, and FeNPs/rGO showed maximum absorption at 232, 265, 395, and 405 nm, respectively. FTIR spectrum showed different functional groups (OH, COOH, C=O), C–O–C) modifying material surfaces. Based on Debye Sherrer's equation, the mean calculated particle size of all synthesized materials was < 100 nm (GO = 60–80, rGO = 90–95, FeNPs = 70–90, Fe/GO = 40–60, and Fe/rGO = 80–85 nm). Graphene-based nanomaterials displayed rough surfaces with clustered and spherical shapes and EDX analysis confirmed the presence of both iron and oxygen in all the nanocomposites. The final nanocomposites produced via the synthetic process degraded approximately 74% of methylene blue. Based on the results, it is plausible to conclude that synthesized FeNPs/rGO nanocomposites can also be used as a potential photocatalyst degrader for other different dye pollutants due to their lower band gap.

Stable Sub‐2‐nm Fe3O4 Particles Confined in P, N Co‐Doped Carbon Derived from the Assembly of DPPF with PCN‐222: A Promising Transfer Hydrogenation Catalyst

AbstractThe nanoconfinement approach for constructing ultra‐small nanoparticles has been effectively utilized in the development of non‐precious metal catalysts. Herein, the catalyst precursor was prepared by host‐guest assembly method, using PCN‐222 as the host and 1,1′‐bis(diphenylphosphino) ferrocene (DPPF) as the guest. After calcination, the sub‐2 nm iron oxide nanoparticles within a phosphorus‐nitrogen co‐doped carbon matrix (Fe3O4@P/N‐CDCM) was obtained. Benefiting from the nanoconfinement effect, the sub‐2 nm Fe3O4 nanoparticles were uniformly dispersed on the P/N‐CDCM matrix. As a representative application, Fe3O4@P/N‐CDCM‐600 showed remarkable catalytic activity in the reduction of various nitroaromatic compounds. Under ambient conditions, the efficient reduction of nitro compounds in aqueous solution led to excellent conversion rates (96–99 %) and selectivity (99 %) within 45 minutes. Additionally, the catalyst maintained high efficiency over 5 cycles without experiencing a noticeable decrease in activity. This work provides an innovative and cost‐effective strategy for fabricating highly dispersed non‐precious metal nanoparticles.

Mechanism of arsenic removal using brown seaweed derived impregnated with iron oxide biochar for batch and column studies

Water contaminated with arsenic presents serious health risks, necessitating effective and sustainable removal methods. This article proposes a method for removing arsenic from water by impregnating biochar with iron oxide (Fe2O3) from brown seaweed (Sargassumpolycystum). After the seaweed biomass was pyrolyzed at 400 °C, iron oxide was added to the biochar to increase its adsorptive sites and surface functional groups, which allowed the binding of arsenic ions. Batch studies were conducted to maximize the effects of variables, including pH, contact time, arsenic concentration, and adsorbent dosage, on arsenic adsorption. The maximum arsenic adsorption efficiency of 96.7% was achieved under optimal conditions: pH 6, the adsorbent dosage of 100 mg, the initial arsenic concentration of 0.25 mg/L, and a contact time of 90 min. Langmuir and Freundlich’s isotherms favored the adsorption process, while the kinetics adhered to a pseudo-second-order model, indicating chemisorption as the controlling step. Column studies revealed complete saturation after 200 min, and the adsorption behavior fits both the Adams–Bohart and Thomas models, demonstrating the potential for large-scale application. The primary mechanism underlying the interaction between iron-modified biochar and arsenic ions is surface complexation, enhanced by increased surface area and porosity. This study highlights the significant contribution of iron-modified biochar derived from macroalgae as an effective and sustainable solution for arsenic removal from water.

Novel ternary nanocomposite (TiO2@Fe3O4-chitosan) system for nitrate removal from water: an adsorption cum photocatalytic approach.

Nitrate pollution of water emerging from various anthropogenic activities has become a major environmental concern because of its deleterious effects on natural water resources. The present work deals with the synthesis of the ternary nanocomposite based on chitosan, iron oxide (Fe3O4), and titanium dioxide (TiO2) and its application for the removal of nitrates from model-contaminated water. Fe3O4 derived through a coprecipitation method was incorporated into the chitosan matrix which was fabricated in the form of beads. The wet gel beads were then successfully coated with sol-gel-derived silver-doped titanium dioxide sol followed by drying under suitable conditions to get the functional nanocomposite beads. The synthesized functional materials were further characterized for their structural, morphological, and textural features using X-ray diffraction analysis, physical property measurement (PPMS), Fourier transform infrared (FTIR) analysis, UV visible spectroscopy analysis (UV-vis), BET surface area analysis (BET), field emission scanning electron microscopic (FESEM), and transmission electron microscopy (TEM) analysis. The ternary nanocomposites were further used for the removal of nitrates via adsorption cum photocatalytic reduction technique from the model contaminated water when subjected to an adsorption study under dark conditions and photocatalytic study under UV/visible/sunlight for a definite time. Fe3O4 in the nanocomposite provides enhanced adsorption features whereas the functional coating of titanium dioxide aids in the removal of nitrates through the photocatalytic reduction technique. The functional beads containing 3% Fe3O4 in the wet gel form (CTA-F3) have excellent nitrate removal efficiency of ~ 97% via adsorption cum solar photocatalysis towards the removal of nitrate ions from 50ppm nitrate solution, whereas the dried nanocomposite beads have got a nitrate removal efficiency of ~ 68% in 1h from 100ppm nitrate solution. Continuous flow adsorption cum photocatalytic study was performed further using the oven-dried functional beads in which flow rate and bed height were varied while maintaining the concentration of feed solution as constant. A nitrate removal efficiency of 65% and an adsorption capacity of 4.1 mgg-1 were obtained for the CTA-F3 beads in the continuous flow adsorption cum photocatalysis experiment for up to 5h when using an inlet concentration of 100ppm, bed height 12cm, and flow rate 5.0mlmin-1. A representative fixed-bed column adsorption experiment conducted using CTA-F3 beads for the treatment of a real groundwater sample shows reasonable results for nitrate removal (71.7% efficiency) along with a significant removal rate for the other anions as well. Thus, the novel adsorbent/photocatalyst developed is suitable for the removal of nitrates from water due to the synergistic effect between Fe3O4, chitosan, and titanium dioxide.

A hybrid FeOx/CoOx/Pt ternary nanocatalyst for augmented catalysis of formic acid electro-oxidation

Platinum-based catalysts that have long been used as the anodes for the formic acid electro-oxidation (FAO) in the direct formic acid fuel cells (DFAFCs) were susceptible to retrogradation in performance due to CO poisoning that impaired the technology transfer in industry. This work is designed to overcome this challenge by amending the Pt surface sequentially with nanosized cobalt (nano-CoOx, fibril texture of ca. 200 nm in particle size) and iron (nano-FeOx, nanorods of particle size and length of 80 and 253 nm, respectively) oxides. This enriched the Pt surface with oxygenated groups that boosted FAO and mitigated the CO poisoning. The unfilled d-orbitals of the transition metals and their tendency to vary their oxidations states presumed their participation in a faster mechanism of FAO. Engineering the Pt surface in this FeOx/CoOx/Pt hierarchy resulted in a remarkable activity toward FAO, that exceeded four times that of the Pt catalyst with up to ca. 2.5 times improvement in the catalytic tolerance against CO poisoning. This associated a ca. − 32 mV shift in the onset potential of FAO which increased to − 40 mV with a post-activation of the same catalyst at − 0.5 in 0.2 mol L–1 NaOH, displaying the catalyst's competitiveness in reducing overpotentials in DFAFCs. It also exhibited a favorable amelioration in the catalytic durability in long-termed chronoamperometric electrolysis. The electrochemical impedance spectroscopy and the CO stripping voltammetry were employed to elucidate the origin of enhancement.

Mixing Order Asymmetry in Nanoparticle-Polymer Complexation and Precipitation Revealed by Isothermal Titration Calorimetry.

In recent years, there has been a renewed interest in complex coacervation, driven by concerted efforts to offer novel experimental and theoretical insights into electrostatic charge-induced association. While previous studies have primarily focused on polyelectrolytes, proteins, or surfactants, our work explores the potential of using cerium (CeO2) and iron (γ-Fe2O3) oxide nanoparticles (NPs) to develop innovative nanomaterials. By combining various charged species, such as polyelectrolytes, charged neutral block copolymers, and coated NPs, we study a wide variety of complexation patterns and compare them using isothermal titration calorimetry, light scattering, and microscopy. These techniques confirm that the titration of oppositely charged species occurs in two steps: the formation of polyelectrolyte complexes and subsequent phase (or microphase) separation, depending on the system studied. Across all examined cases, the entropic contribution to the total free energy surpasses the enthalpic contribution, in agreement with counterion release mechanisms. Furthermore, our investigation reveals a consistent asymmetry in the reaction enthalpy associated with the secondary process, with exothermic profiles observed upon the addition of cationic species to anionic ones and endothermic profiles in the reverse case.

Circular Steel for Fast Decarbonization: Thermodynamics, Kinetics, and Microstructure Behind Upcycling Scrap into High-Performance Sheet Steel

Steel production accounts for approximately 8% of all global CO2 emissions, with the primary steelmaking route using iron ores contributing approximately 80% of those emissions, mainly due to the use of fossil-based reductants and fuel. Hydrogen-based reduction of iron oxide is an alternative for primary synthesis. However, to counteract global warming, decarbonization of the steel sector must proceed much faster than the ongoing transition kinetics in primary steelmaking. Insufficient supply of green hydrogen is a particular bottleneck. Realizing a higher fraction of secondary steelmaking is thus gaining momentum as a sustainable alternative to primary production. Steel production from scrap is well established for long products (rails, bars, wire), but there are two main challenges. First, there is not sufficient scrap available to satisfy market needs. Today, only one-third of global steel demand can be met by secondary metallurgy using scrap since many steel products have a lifetime of several decades. However, scrap availability will increase to about two-thirds of total demand by 2050 such that this sector will grow massively in the next decades. Second, scrap is often too contaminated to produce high-performance sheet steels. This is a serious obstacle because advanced products demand explicit low-tolerance specifications for safety-critical and high-strength steels, such as for electric vehicles, energy conversion and grids, high-speed trains, sustainable buildings, and infrastructure. Therefore, we review the metallurgical and microstructural challenges and opportunities for producing high-performance sheet steels via secondary synthesis. Focus is placed on the thermodynamic, kinetic, chemical, and microstructural fundamentals as well as the effects of scrap-related impurities on steel properties.

Co-wetting behavior of molten slag and iron on carbon materials in blast furnace

The interaction between molten slag, liquid iron, and carbon is one of the most typical and complex multiphase flow behaviors in the high-temperature zone of blast furnace. The wetting behavior among these phases is the most fundamental characteristic that determines their interactions. This research focuses on the co-wetting behavior of molten slag and iron on graphite, using high-temperature experiments and atomistic simulations. The results revealed that the multiphase cooperative reaction wetting process is influenced by multiple factors. The wettability of molten iron is mainly affected by its initial carbon content, while the wettability of slag is influenced by both the initial carbon content of the molten iron and its own compositional changes. The initial carbon content in molten iron affects the carburizing reaction, which in turn influences the wetting mechanism between molten iron and graphite. Additionally, it alters the reaction of FeO in the slag, thereby modifying the properties of the slag-carbon interface and affecting the overall co-wetting process. Meta-dynamic calculations showed that the reduction of molten iron oxide by dissolved carbon is significantly more effective than that by solid graphite carbon, demonstrating that the behavior of carbon between iron and slag is a key factor in the multiphase cooperative reaction process.

The effect of carbon coating on the arsenite sorption by magnetic carbon nanocomposites

AbstractArsenic pollution has emerged through anthropogenic activities and natural mineral leaching processes. This study aims to advance the use of magnetic carbon nanocomposites (MCNs) in the sorption of arsenic, studying the influence of feedstock and the presence of carbon coating on magnetic nanoparticles. Previous works have shown that post-pyrolysis treatment improves the stability of MCNs by reducing iron leaching due to the formation of a carbon coating that encapsulates the iron oxide nanoparticles. However, this carbon coating could influence the adsorption properties of MCNs. This investigation deals with arsenic adsorption by four MCNs prepared by co-precipitation of magnetite (Fe3O4) nanoparticle into four carbonaceous matrixes, followed by a post-pyrolysis treatment. The pristine carbonaceous matrixes used in the present work were commercial activated carbon (CAC), charcoal (CC), hydrochar from the orange residue (HCOR), and biochar from sunflower husk (BCSFH). Pristine carbonaceous materials and MCNs without post-pyrolyzed were also used as arsenic sorbents in water solutions. Additionally, kinetic studies were carried out to explore the sorption properties of different MCNs and pristine materials, concerning the removal efficiencies (expressed as a percentage) and adsorption capacities, determining the equilibrium time. The results demonstrated that the presence of magnetite increases the adsorption of arsenic, being higher in the case of materials obtained by direct co-precipitation than in materials subjected to a post-pyrolysis process. The presence of a carbon layerprotecting the magnetite slightly decreases the adsorption of arsenic.

The impact of ammonium hydroxide flow rate on iron oxide nanoparticle hydrodynamic size and colloidal stability

Precise control over the synthesis of iron oxide nanoparticles is essential to achieving optimal particle characteristics such as size, hydrodynamic size, polydispersity index, and zeta potential, all of which significantly influence colloidal stability. The commonly used co-precipitation technique often leads to high polydispersity and variable particle sizes, resulting in poor colloidal stability. This study demonstrates that varying the ammonium hydroxide flow rate during co-precipitation significantly affects particle size, hydrodynamic size, aggregation, and colloidal stability. An optimal flow rate of 4.25 mmol/min produced smaller, more uniform, and colloidally stable nanoparticles. Nanoparticle tracking analysis showed that this flow rate resulted in the smallest and most consistent hydrodynamic size of 123.3 ± 0.7 nm, while both higher and lower flow rates yielded larger and more polydisperse particles, up to 155.8 ± 20 nm. Dynamic light scattering confirmed that the 4.25 mmol/min rate produced the lowest polydispersity index of 0.21 ± 0.04, indicating the highest uniformity. Additionally, UV-Vis measurements demonstrated that nanoparticles synthesized at this optimal flow rate exhibited minimal changes in absorbance over 24 h, indicating superior colloidal stability. This study highlights the importance of optimizing the flow rate during the co-precipitation synthesis of IONPs to control particle hydrodynamic size and polydispersity, which are crucial parameters for numerous biomedical, chemical, and environmental applications.