Formation Of Fe3O4 Research Articles

Efficient synthesis of FeVO4 cathode materials in high specific energy thermal batteries

Thermal batteries, which are essential for applications in extreme environments, require cathode materials with high specific energy and thermal stability. In this study, metal vanadates were synthesized via a chemical precipitation method followed by high-temperature sintering, offering a promising alternative for conventional transition metal sulfides. The synthesized FeVO4 exhibits phase purity, while copper and nickel vanadates show secondary phases, indicating challenges in achieving pure-phase synthesis of metal vanadates. Electrochemical evaluations reveal that FeVO4 cathode delivers an initial discharge voltage of 2.65 V and a specific capacity of 190 mAh/g. Whereas the FeVO4/CNTs composite cathode demonstrates an enhanced specific capacity of 253.66 mAh/g, which is attributed to prolonged discharge plateaus. Phase evolution studies indicated that FeVO4 reacts with molten salts during high-temperature discharge, leading to the formation of Fe2O3 and Li0.3V2O5, which contribute to the observed stepwise discharge behavior. These results emphasize the importance of optimizing the interactions between cathode materials and molten salts to improve the performance of high-temperature thermal batteries.

Protection of 316L Steel Against LBE Corrosion by a CaO-MgO-Al2O3-SiO2 Glass–Ceramic Coating

A CaO-MgO-Al2O3-SiO2 glass–ceramic coating was prepared by the slurry method and subsequent sintering to improve the corrosion resistance of 316L steel in liquid lead–bismuth eutectic alloy at high temperatures. The glass–ceramic coating, sintered at 884 °C, was dense and demonstrated strong adhesion to the substrate. It was composed of the crystalline phases diopside (CaMgSi2O6) and anorthite (CaAl2Si2O8) and had an average Vickers hardness of 595 HV, which was over three times that of 316L steel. After corrosion in an oxygen-saturated, static lead–bismuth eutectic alloy at 500 °C for 1000 h, the uncoated 316L experienced significant mass gain (0.04 g) due to severe oxidative corrosion, resulting in the formation of Fe3O4 and Pb2O on its surface. In contrast, the glass–ceramic-coated specimens showed a very small mass gain (0.0012 g) after corrosion. The coating maintained good thermal stability; its crystalline phase composition remained largely unchanged after the corrosion test. The glass–ceramic coating still exhibited dense microstructure and tightly adhered to the substrate after corrosion. There was no evident penetration of lead–bismuth into the coating, and no dissolution of the coating’s elements into the lead–bismuth alloy was detected. These observations confirm that the glass–ceramic coating possessed superior corrosion resistance in liquid lead–bismuth eutectic environments.

CuO and spinel CuCo2O4 supported on mesoporous nanocubes with dual redox-active centers for electrocatalytic H2O2 reduction and sensing

The copper hexacyanoferrate (CuHCF) nanocube and its cobalt-substituted analogue (CoCuHCF) possess numerous micropores; however, they demonstrate limited electrocatalytic performance for H2O2 reduction. Heat treatment of CuHCF in air (CuHCF-ht) results in the formation of CuO and Fe3O4 with noticeable aggregation. In contrast, the heat treatment of CoCuHCF in air (CoCuHCF-ht) preserves its nanocube structure while also forming a spinel CuCo2O4 phase. The partial substitution of cobalt ions for copper ions in CuHCF enhances both thermal and structural stability, leading to the transformation of micropores into mesopores during heat treatment. This transformation improves electrolyte accessibility and structural integrity. The CoCuHCF-ht electrode features dual redox-active centers (Cu+/Cu2+ couple) derived from the CuO and CuCo2O4 phases, serving as catalytic redox mediators for H2O2 reduction. This dual redox activity results in superior performance for H2O2 reduction compared to CuHCF-ht, which only exhibits a single pair of Cu+/Cu2+ couple from CuO as an active mediator. This enhanced performance is evidenced by a lower Tafel slope, a higher catalytic rate constant, and improved mass transfer of analytes. The CoCuHCF-ht catalyst, characterized by dual redox-active centers in mesoporous nanocubes, demonstrates a high sensitivity of 234.03 μA mM−1 cm−2 and a low limit of detection (0.26 μM), along with high selectivity, stability, repeatability, and reproducibility.

Heterogeneous Fenton system driven by magnetic graphene-like biochar for degrading tetracycline

In this study, a novel catalyst with high efficiency and low cost was synthesized from farmland waste peanut shells by one-step pyrolysis modification method via K2FeO4, and employed for the catalytic degradation of tetracycline (TC). The magnetic potassium ferrate modified graphene-like biochar catalyst (PFGB) exhibited a high porosity, a highly graphitized structure, and a large specific surface area (857.09 m2·g-1) which was almost 30 times higher compared with peanut shell biochar, and were found to contain more functional groups. The formation and distribution of Fe3O4 and Fe0 nanoparticles on the surface/pores of PFGB provided more active sites for promoting adsorption and catalytic degradation reactions, and accelerated Fe(II)/Fe(III) recycle. Under the optimal conditions (pH=3.5, catalyst dosage = 0.5g·L-1, H2O2 concentration = 10mmol·L-1), about 98% of TC were degraded within 90min when the initial concentration of TC was 150mg·L-1, and PFGB could perform effectively over a wide pH range of 3-6. Furthermore, PFGB exhibited the advantages of convenient magnetic separation and strong reusability, maintaining a TC removal rate of ~90% after five cycles of experiments. The results of free radical quenching experiment and electron spin resonance analysis revealed that •OH and 1O2 were the main active species in the radical and non-radical pathways, respectively. This study indicated that PFGB, a catalyst developed for heterogeneous Fenton-like systems, possessed high efficiency, stability and reusability, and could be promising for the removal of TC in wastewater and other polluted waters.

Facile microwave synthesis of various-shaped magnetite/ reduced graphene oxide heterostructures and their magnetization properties

Heterostructures of magnetite (Fe3O4) nanoparticles and reduced graphene oxide (RGO) sheets are very common composite materials for different applications such as catalysis, energy storage, and biomedicine. Developing methods for the facile control of the size and shape of both freestanding Fe3O4 nanoparticles and those anchored onto RGO sheets is in demand. Herein, we report on the rapid and facile microwave synthesis (MWS) of Fe3O4 nanoparticles and Fe3O4/RGO with various sizes and shapes using the oleylamine (OAm)/oleic acid (OAc) ligand pair. The solvothermal synthesis using microwave irradiation (MWI) resulted in the concurrent conversion of graphene oxide (GO) into RGO and the in-situ formation of various-shaped Fe3O4 on RGO sheets. Freestanding Fe3O4 nanoparticles of various shapes were prepared using MWS for comparison. The morphological, structural, and surface properties of the samples were studied using different characterization techniques. The magnetization properties of the prepared samples were determined using a vibrating sample magnetometer. Various-shaped standalone and RGO-supported Fe3O4 nanoparticles including nanospheres, nanocubes, and nanotriangles were synthesized via MWI at 1000 W for 20 min by changing the ratios of the iron precursor and the OAm/OAc ligand pair. Interestingly, the MWI using OAm/OAc ligand pair of a molar ratio of 3:4 resulted in the in-situ formation of large hexagonal Fe3O4/RGO. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results confirm the crystallinity and spinel structure of the prepared Fe3O4 samples and prove the concurrent conversion of GO into RGO with assemblies of Fe3O4 nanoparticles. The magnetization measurements further emphasized the role of size and shape in affecting the magnetic properties of Fe3O4 and Fe3O4/RGO heterostructures. The results identify the qualities of the prepared samples and prove the MWS as a facile one-pot method for the preparation of Fe3O4 and Fe3O4/RGO heterostructures.

Effects of H2S content on the corrosion behavior of gas storage reservoir injection and production pipeline steel in CO2-H2S environment

The effects of H2S content on the corrosion behavior of gas storage reservoir injection and extraction pipeline steel in a CO2-H2S environment were investigated by surface characterization and ultrasonic thickness measurement. The results show that the corrosion products of gas injection and extraction pipelines under real conditions are more complex. In the CO2-H2S environment, with the increase of H2S content, the corrosion rate of gas storage reservoir gas injection and extraction pipeline steel firstly increases and then decreases. At a partial pressure ratio of CO2 to H2S of 550, corrosion resulted mainly in the formation of FeCO3, FeS2, and Fe3O4, with limited generation of stabilizing protective films. This led to severe localized corrosion, mainly driven by CO2. In contrast, when the CO2 to H2S partial pressure ratio was reduced to 5.2, the corrosion mainly produced Fe7S8, FeS2, and BaSO4, which promoted the formation of a more stable protective film on the inner wall of the tube, while the presence of gums reduced the severity of the localized corrosion and shifted the corrosion control to H2S.

Improved electrochemical performance of Fe3O4/TiO2 composite thin film electrode for energy storage applications

This study is the first attempt to examine the electrochemical properties of TiO2 composite with Fe3O4 thin film. In our analysis, X-Ray diffraction (XRD) confirms the formation of Fe3O4 on TiO2. Fourier Transform Infrared Spectroscopy (FT-IR) and Raman spectroscopy confirmed the functional groups. The UV–Vis spectroscopy analysis shows that the addition of Fe3O4 results in decrease in optical band gap. Our Cyclic Voltammetry (CV) results demonstrate that, under steady state conditions, the behaviors of TiO2 and Fe3O4/TiO2 electrodes regarding ion adsorption and charge transmission vary. Pseudocapacitive effects and charge transfer affects the functionality of the TiO2 electrode, whereas two-layer capacitance effects primarily control the response of the Fe3O4/TiO2 electrode. Numerous factors, including ion diffusion, rate capability, charge transfer, and series resistance, can be directly determined using electrochemical impedance spectroscopy (EIS). The experimental results and analysis presented in this work brings to light the significance of Fe3O4 in the electrochemical response of an electrode-electrolyte interface.

Insight into the stabilization mechanism of Zn during co-gasification of sewage sludge and coal: Perspective of solid-liquid transition

In this study, the underlying mechanism of zinc (Zn) stabilization during the co-gasification of sewage sludge (SS) with Shenmu coal (SM) was investigated using an in-situ visual furnace to analyze the distribution of Zn species. The findings classified two distinct stages within the co-gasification process: the organic matter gasification stage, occurring below 1000 °C, and the inorganic mineral melting stage, occurring above 1000 °C. The addition of SM can extend the organic matter gasification phase, in which the porous carbon structure of the SM char aids in the capture of Zn released during the devolatilization of SS. However, a sustained reducing atmosphere promoted the formation of Fe3O4, causing Zn destabilization. Subsequently, during the inorganic mineral melting stage, the complete reaction of carbon released Zn, which was adsorbed onto the carbon surface. Furthermore, the ash from SM contributes to the melting of the co-gasification residues, enhancing Zn stabilization through encapsulation by the molten phase and stabilization within the spinel lattice. This study highlights the critical role of liquid encapsulation in Zn stabilization during co-gasification.

Long-Term Evaluation of a Ternary Mixture of Molten Salts in Solar Thermal Storage Systems: Impact on Thermophysical Properties and Corrosion.

Solar thermal plants typically undergo trough operational cycles spanning between 20 and 25 years, highlighting the critical need for accurate assessments of long-term component evolution. Among these components, the heat storage media (molten salt) is crucial in plant design, as it significantly influences both the thermophysical properties of the working fluid and the corrosion of the steel components in thermal storage systems. Our research focused on evaluating the long-term effects of operating a low-melting-point ternary mixture consisting of 30 wt% LiNO3, 57 wt% KNO3, and 13 wt% NaNO3. The ternary mixture exhibited a melting point of 129 °C and thermal stability above 550 °C. Over 15,000 h, the heat capacity decreased from 1.794 to 1.409 J/g °C. Additionally, saline components such as CaCO3 and MgCO3, as well as lithium oxides (LiO and LiO2), were detected due to the separation of the ternary mixture. A 30,000 h exposure resulted in the formation of Fe2O3 and the presence of Cl, indicating prolonged interaction with the marine environment. This investigation highlights the necessity of analyzing properties under actual operating conditions to accurately predict the lifespan and select the appropriate materials for molten salt-based thermal storage systems.

Corrosion behavior of Q345 and Q235 steels in simulated neutral soil solution

Abstract Q345 and Q235 steels are widely used in infrastructure and manufacturing. Examining the corrosion behavior of two types of steel in a neutral soil environment can facilitate the assessment of the service life of the steel machinery, thereby mitigating potential corrosion failures. In order to investigate the corrosion and mechanism of Q345 and Q235 steels in the neutral soil solution, an electrochemical test, scanning electron microscopy, and X-ray diffraction were employed to analyze the corrosion morphology, corrosion product, and electrochemical polarization curves. The results showed that no visible pitting pits were observed on the surfaces of Q345 steel and Q235 steel. The corrosion types were mainly overall corrosion in the simulated neutral soil solution. The microstructure of Q235’s corrosion product exhibits greater compactness, facilitating the formation of Fe3O4. This compound demonstrates excellent binding ability with the metal matrix and hinders the continuous corrosion of the steel. Q235 steel has better corrosion resistance with a lower corrosion rate than Q345 steel in the simulated neutral soil solution. These findings contribute valuable information for material selection considerations in manufacturing machinery in neutral soil environments.

Nano-photosensitizers with gallic acid-involved Fe–O–Cu “electronic storage station” bridging ligand-to-metal charge transfer for efficient catalytic theranostics

NH2-MIL-88B (Fe) (MOF) is a promising photocatalytic material for antitumor therapy because of its distinctive electronic structure. However, inadequate separation of photo-generated electrons and slow reaction rate in low/high-valence iron (Fe) cycles limit their clinical application. In the present study, “electronic storage station” as a ligand-to-metal charge transfer bridge bond was constructed to inhibit recombination of electron/hole under 650 nm laser irradiation. Cupric (Cu) ions and gallic acid (GA) were self-assembled into a MOF (denoted as CGMOF) to create an FeO(GA)Cu bridge bond. GA, characterized by robust electron delocalization and abundant electron-donating groups, significantly enhances electron transfer efficiency for photodynamic therapy (PDT). CGMOF can respond to endogenous glutathione and release cuprous ions, accelerating the iron ion/ferrous ion cycles for chemodynamic therapy (CDT). The released Fe species can serve as T2-weighted magnetic resonance imaging contrast. Extended X-ray absorption fine structure spectra confirmed the presence of GA-containing FeOCu bonds in CGMOF. Furthermore, a series of photo-electrochemical tests confirmed that the formation of FeO(GA)Cu bond prominently elevated the redox capacity and increased the carrier density of CGMOF by 2.74-fold compared to that of MOF. In addition, cinnamaldehyde was grafted onto CGMOF for tumor-responsive hydrogen peroxide self-supply. Concurrently, hyaluronic acid was surface-modified to achieve the targeted delivery of nano-photosensitizers. In summary, this study presents an innovative approach for engineering Fe-based metal–organic frameworks for synergetic PDT/CDT applications.

Decorated palladium nanoparticles over chitosan-agarose encapsulated Fe3O4 microspheres: Investigation of its catalytic efficiency in the Suzuki-Miaura coupling reactions

The enhanced properties of heterogeneous catalysts have led to significant interest in recent years, particularly in composite materials that incorporate organic-inorganic systems. In this particular study, a series of steps were undertaken to synthesize Fe3O4 microspheres, which were subsequently coated with chitosan and agarose. Finally, palladium nanoparticles were immobilized onto the surface of the microspheres, resulting in the formation of Fe3O4 MPs@CS-Agar/Pd NPs. To evaluate the material, advanced analytical techniques such as FT-IR, FESEM-EDS, ICP-OES, TEM, XRD, and VSM were utilized to determine its structural and physicochemical characteristics. The results shown that the Pd nanoparticles were formed in nanometer-sized particles, exhibiting a quasi-spherical shape with an average diameter ranging from 20–40 nm. Notably, the Fe3O4 MPs@CS-Agar/Pd NPs exhibited remarkable catalytic activity in Suzuki-Miyaura reaction. Importantly, the nanocatalyst could be reused up to 8 times without any decline in its activity. The exceptional catalytic performance of the Fe3O4 MPs@CS-Agar/Pd NPs in these reactions can be attributed to the distinctive nanostructure characteristics it possesses.

Effect of heat treatment on the microstructure, LBE corrosion resistance, and bonding strength of the FeCrAl‐based coatings

AbstractThe bonding strength and LBE corrosion resistance of the Fe15Cr11Al2Si, Fe15Cr11Al0.5Y, and Fe15Cr11Al2Si0.5Y coatings heat‐treated at 500–650°C for 500 h were investigated. The results showed that the as‐deposited Fe15Cr11Al0.5Y coating has the strongest bonding strength with the F/M steel cladding tube compared with the Fe15Cr11Al2Si and Fe15Cr11Al2Si0.5Y coatings. Heat treatment deteriorates the bonding performance of the coatings, and obvious enrichment of Cr and Al elements appeared. The consumed Al element inside the heat‐treated coatings promotes the formation of Fe3O4 on the surface of the coatings after the corrosion test. The Y element can inhibit the enrichment of elements and the formation of Fe3O4. The bonding strength of the heat‐treated coatings can be improved after the corrosion test. The underlying mechanism of the evolution of microstructure and properties of the coatings after heat treatment and corrosion test was discussed.

Fluctuating Flame from Suspending Ferrimagnetic Core/Shell Al@Fe3O4 Nanoparticles in a Magnetic Field

AbstractCore–shell fuel@oxidizer nanocomposite can combust in oxygen‐starved environment. A ferrimagnetic reactive particle, being successfully engineered, allows for manipulation using an external magnetic field and facilitates target heat or gas production. This research reports on interesting flame dynamics of newly synthesized core–shell Al@Fe3O4 nanoparticles under the influence of a magnetic field. Serving as an oxidizer and a functional ferrimagnetic component, iron oxide nanoparticles (IONPs) are grown in situ on nano‐sized Al (n‐Al) particles. Electron microscopic images demonstrate nearly monodispersed IONPs ≈7 nm decorating the surface of n‐Al. X‐ray diffractogram and X‐ray photoelectron spectroscopy confirm the formation of Fe3O4. Thermal analysis suggests the as‐prepared core–shell particles predominantly go through a solid‐state reaction mechanism that exhibits 30% lower activation energy compared to physically‐mixed nanocomposite (215.0 vs 310.8 kJ mol−1). The core/shell particles can be ignited and combust under laser irradiation with or without the effect of a magnetic field. When suspended in the middle of the tube by the magnetic field, an interesting combustion process is observed, highlighting a grow‐shrink‐grow flame resulted from the interactions between the combustion products and the external magnetic field, as well as backfiring at the bottom of the sample without major changes in burning rate and ignition delay.

Iron Oxide Direct Reduction and Iron Nitride Formation Using Ammonia: Review and Thermodynamic Analysis

The steel industry is one of the main contributors to global greenhouse gas emissions, responsible for about 7 to 9% of the world’s total output. The steel sector is under pressure to move toward net-zero emissions by reducing its consumption of coke as the main method of reducing iron-rich feed materials to iron. Due to its well-developed synthesis process, high supply chain, straightforward handling technologies, and highly developed long-standing infrastructure, ammonia has the potential to become a replacement for coke as a future iron ore reductant. This work reviews previous research on ammonia direct reduction of iron oxides and the possible formation of iron nitrides. A thermodynamic assessment using FactSage 8.2 thermochemical software was carried out examining the behavior of ammonia gas as the reductant upon heating, detailed evaluations of the stable phases present under different reaction conditions and using different feed materials, and the formation and stability of iron nitride phases. The results suggest that the reduction of hematite with ammonia occurs in two steps below 570 °C and three steps above 570 °C. The ratio of Fe2O3/NH3 was predicted to affect the reduction reactions by promoting a greater reduction degree and simultaneously lowering the initial temperature needed for reduction, while the excess gas concentration can suppress FeO formation. A predominance area diagram was developed showing the main areas of stable phases as a function of the partial pressure of NH3 and temperature. The formation of iron nitrides during the process was predicted and these were not expected to cause issues for the formation of iron due to their instability under the conditions studied. This analysis can be used to inform further experimental studies regarding ammonia reduction of iron oxide.Graphical

Fe, Cu-decorated carbon material produced from ionic liquids as resourceful electrocatalyst for water splitting

The quest for highly efficient, stable, and economically viable bifunctional electrocatalysts is of paramount relevance for advancing in water splitting for the hydrogen energy sector, particularly in facilitating hydrogen (HER) and oxygen evolution evolution (OER) as cathodic and anodic reaction, respectively. In this study, two ionic liquids containing transition metal Fe or Cu, as well as a mixture of these ionic liquids, were used as precursors to synthesize Fe-, Cu-, and Fe,Cu-decorated carbon materials through simple, straightforward, and inexpensive carbonization processes. Comprehensive characterization via SEM-EDS, TEM, XRD, and XPS established the formation of Fe3O4 and Cu2O species. These materials were systematically evaluated for OER and HER in alkaline electrolyte. Fe,Cu-decorated carbon electrocatalyst exhibited favorable performance for OER, including a low onset potential, and reaching 10 and 50 mA cm−2 at overpotential values of 325 mV and 364 mV, respectively. Notably, grafting both Fe and Cu in the material further augmented its electrocatalytic properties, underscoring the enhanced potential of transition metal-decorated carbon materials for OER applications.

Impact of cerium on microstructure of rust and corrosion resistance of Cu-Cr-Ni-V micro-alloyed steels in NaHSO3 acid accelerated test

Corrosion resistance, microstructure and corrosion products of rust and inclusions of Cu-Cr-Ni-V micro-alloyed steels containing 0.0015% cerium (Ce) were investigated by NaHSO3 acid-accelerated test. The results revealed the presence of three-layer microstructures in rust: bottom layer (Fe3O4), interface layer(α-FeOOH) and cracks layer(α-Fe2O3) from inner to outside. The introduction of cerium facilitated the formation of α-FeOOH and Fe3O4 in the rust, while reducing the prevalence of α-Fe2O3 in the rust. The type of inclusions transitioned from undissolved inclusions to dissolved Ce-based inclusions in the acid solution and corrosion rate was reduced by 27% by adding the Ce to the micro-alloyed steels.

Polyaniline grafted Fe3O4@ZnO/GO as a recyclable photocatalyst

A novel superparamagnetic Fe3O4@ZnO/GO (F@Z/G) nanocomposites with different ratios: (1/1, 1/2, 1/3 wt%) of Fe3O4@ZnO core–shell to GO were synthesized using the hydrothermal method. XRD and TEM images indicated the formation of magnetite Fe3O4 and ZnO in the form of core–shell,which were uniformly loaded on GO sheets. In the next step, OH and COOH functional groups of F@Z and GO in F@Z/G nanocomposites used as initiators for in situ polymerization of aniline and polyaniline grafted F@Z/G nanocomposites were named as (F@Z/G1-P, F@Z/G2-P, F@Z/G3-P) were successfully produced. The Formation of polyaniline on F@Z/G nanocomposite was confirmed using FTIR, and XRD. The presence of polyaniline in F@Z/G nanocomposites not only retained their superparamagnetic property of F@Z/G nanocomposites as recyclable photocatalysts for degradation of methylene blue but also increased their degradation efficiency by speeding up the electron-hole production. The Maximum removal efficiency under the same conditions was obtained for F@Z/G2-P nanocomposite which reached 96.10 % during 40 min.

Potential Utilization of Iron Oxidation Reaction Heat for the Generation of SiO2–FeO System Melts

Silicon-containing steel forms an oxide layer within the scale during hot rolling. This layer comprising oxides such as Fe2SiO4 and FeO adversely affect the surface quality of steel owing to strong adhesion between Fe2SiO4 and the steel substrate. A method to melt this silicon-containing oxide layer through the oxidation reaction of iron plates by applying SiO2 powder to the surface is proposed. The aim of this study is to understand the reaction mechanism and identify the optimal conditions for this process. Application of SiO2 coating to the surface of an iron plate at 6.67 × 10–4 g·mm−2 and maintaining the plate at 1423 K, just below the eutectic temperature of Fe2SiO4–FeO system (1450 K), cause the surface oxide scale to melt when exposed to oxidation in an atmospheric environment. Notably, reducing the electric furnace temperature hinders the melting process, whereas excessive application of SiO2 hampers the formation of sufficient liquid phase. On the surface of the iron plate, primarily FeO and Fe2SiO4 are formed. Heat generation is mainly due to the formation of FeO, which leads to the rapid generation of Fe2SiO4. Eutectic reactions within SiO2–Fe2SiO4 or FeO–Fe2SiO4 systems drive the formation of the liquid phase. Once the liquid phase was established, rapid diffusion of iron ions within it resulted in rapid iron oxidation and additional heat generation. Ultimately, a liquid phase in equilibrium with FeO is formed across the entire surface of the iron plate.

Kinetic study of the reduction reaction of red mud and CO under fluidization condition

AbstractPyrometallurgical method of iron recovery from red mud (RM) has advantages of simple procedures, high recovery efficiency and significant waste minimization. The fluidization reduction process using CO as reductant addresses the issues of high energy consumption and long reaction time of pyrometallurgical method. In order to optimize the operational conditions of the fluidization reduction process, it is necessary to study the reaction characteristics of RM and CO under fluidization condition. In response to the problems of the current kinetic study including the unsatisfied fluidization condition and possible errors introduced by the estimation method, we carried out improvements in both experiment and data processing. In the experiment aspect, thermo‐gravimetric analyzer (TGA) test rig with large sample capacity and gas flow was established, and approximate fluidization condition was achieved by intensifying diffusion by increasing the gas flow rate and decreasing the sample mass. In the data processing aspect, we developed a program with data cleaning and kinetic function fitting capabilities, and the goodness of fit was evaluated by Akaike information criterion (AIC). The results indicated that within the temperature range of 500–600°C and CO concentrations of 5%–15%, the reaction between RM and CO can be divided into two steps based on the criterion of complete formation of Fe3O4. The first step reaction has a relatively fast reaction rate, conforming to the F1 kinetic function with rate equation given as . The second step reaction displays a more complex pattern and the fitted rate equation is . The obtained results could provide a reliable reference for the operational design of the fluidization reduction of RM.