Formation Of Fe3O4 Research Articles

Investigation of the migration of natural organic matter-iron-antimony nano-colloids in acid mine drainage

Colloids can potentially affect the efficacy of traditional acid mine drainage (AMD) treatment methods such as precipitation and filtration. However, it is unclear how colloids affect antimony (Sb) migration in AMD, especially when natural organic matter (NOM) is present. To conduct an in-depth investigation on the formation and migration behavior of NOM, iron (Fe), Sb and NOM-Fe-Sb colloids in AMD, experiments were performed under simulated AMD conditions. The results demonstrate significant variations in the formation of NOM-Fe-Sb colloids (1–3–450 nm) as the molar ratio of carbon to iron (C/Fe) increases within acidic conditions (pH = 3). Increasing the C/Fe molar ratio from 0.1 to 1.2 resulted in a decrease in colloid formation but an increase in particulate fraction. The distribution of colloidal Sb, Sb(III), and Fe(III) within the NOM-Fe-Sb colloids decreased from 68 % to 55 %, 72 % to 57 %, and 68 % to 55 %, respectively. Their distribution in the particulate fraction increased from 28 % to 42 %, 21 % to 34 %, and 8 % to 27 %. XRD, FTIR, and SEM-EDS analyses demonstrated that NOM facilitates the formation and crystallization of Fe3O4 and FeSbO4 crystalline phases. The formation of the colloids depended on pH. Our results indicate that NOM-Fe-Sb colloids can form when the pH ≤ 4, and the proportion of colloidal Sb fraction within the NOM-Fe-Sb colloids increased from 9 % to a maximum of 73 %. Column experiments show that the concentration of NOM-Fe-Sb colloids reaches its peak and remains stable at approximately 3.5 pore volumes (PVs), facilitating the migration of Sb in the porous media. At pH ≥ 5, stable NOM-Fe-Sb colloids do not form, and the proportion of colloidal Sb fraction decreases from 7 % to 0 %. This implies that as pH increases, the electrostatic repulsion between colloidal particles weakens, resulting in a reduction in the colloidal fraction and an increase in the particulate fraction. At higher pH values (pH ≥ 5), the repulsive forces between colloidal particles nearly disappear, promoting particle aggregation. The findings of this study provide important scientific evidence for understanding the migration behavior of NOM-Fe-Sb colloids in AMD. As the pH gradually shifts from acidic to near-neutral pH during the remediation process of AMD, these results could be applied to develop new strategies for this purpose.

Effect of formic acid (HCOOH) on the corrosion protectiveness of magnetite (Fe3O4) at elevated temperature

The corrosion behavior of carbon steel in an aqueous solution containing dissolved CO2, H2S, and HCOOH at high temperature was investigated by conducting a series of systematic experiments. The influence of each (possible) corrosive species (CO2, H2S, and HCOOH) on corrosion mechanisms were explored through detailed analysis of corrosion rates and corrosion product layers. The results showed that the formation and integrity of the Fe3O4 layer was compromised in the presence of HCOOH, probably due to the formation of Fe(COOH)+which impedes the formation of Fe3O4 at the initial stage of the corrosion process.

Crystalline phase transformation of Sr-Fe based oxygen carriers modulate the cyclic performance for syngas and CO coproduction in chemical looping ethanol reforming coupled with CO2 splitting

The chemical looping reforming coupled with CO2 splitting (CLR-CS) offers a promising solution for syngas production and simultaneous decomposition of CO2. In this study, the Sr-Fe based oxygen carriers (OCs) were evaluated in CLR-CS using ethanol as fuel. The presence of Sr significantly improved the oxidation performance of iron oxides. The Sr element in fresh Sr-Fe based OCs mainly formed two crystal phases, including SrFe12O19 and Sr4Fe6O13. Increasing the amount of Sr element made it easier to form Sr4Fe6O13 crystal phase. The Sr4Fe6O13 was favorable for syngas production, due to the higher surface oxygen vacancy formation energy with a range of 3.13–3.37 eV. However, the lower oxygen transfer capacity (OTC) of Sr4Fe6O13 resulted in a lower CO yield in the of stage of CO2 decomposition. Compared with Sr4Fe6O13, SrFe12O19 exhibited the higher OTC and the higher reactivity of lattice oxygen, which was preferable to produce more CO2 in the stage of ethanol reforming in fuel reactor. During the cycle tests, the crystalline phase of SrFe12O19 didn’t regenerate under the CO2 atmosphere but transformed into Sr4Fe6O13. It was attributed to the lower energy barrier of CO2 oxidation on the oxygen defect surface of Sr4Fe6O13. The phase transformation of SrFe12O19 accompanied the formation of Fe3O4. The excessive Fe3O4 had poor stability and inactivated easily due to sintering and agglomeration in Sr1Fe4 and Sr1Fe6 samples. The Sr1Fe2, namely the molar ratio of SrO to Fe2O3 of 1:2, exhibited the better performance for syngas (0.291 Nm3/kg OC) and CO (0.141 Nm3/kg OC) coproduction at 800 °C. Additionally, the Sr1Fe2 presented an excellent cyclic stability in 30 cycles due to the suitable proportion of Sr4Fe6O13 and iron oxides formed, which maintained a high syngas yield and avoided sintering of iron oxides. Overall, the Sr1Fe2 is a promising OC candidate in CLR-CS process.

Simultaneous and fast degradation of methylene blue, methylene orange, and Rhodamine B dyes by high-performance rGO/Fe3O4/ZnSe magnetic nanocomposites

Dark catalyst materials are a new generation of catalyst material for the removal of dye and pigment molecules from water and wastewater. In this research, reduced graphene oxide (rGO)/Fe3O4/ZnSe magnetic nanocomposites were used as dark catalyst nanomaterial for ultrafast degradation of methylene blue (MB), Rhodamine B (RB), and methylene orange (MO) dyes in darkness. The obtained results showed that rGO/Fe3O4/ZnSe nanocomposite had excellent dark catalyst ability and could completely remove MB, RB, and MO dyes from water. Also, rGO/Fe3O4/ZnSe nanocomposite degraded these dyes simultaneously in 4 min stirring in the darkness. The obtained results showed that the degradation process was independent to the pH of the effluent. RGO/Fe3O4/ZnSe magnetic nanocomposite was synthesized by a refluxing method. The prepared magnetic nanocomposites were characterized by different analyses such as XRD, FT-IR, Raman, TEM, FESEM, Zeta, EDS, and VSM. The XRD analysis and TEM images confirmed the successful formation of ZnSe and Fe3O4 on GO nanosheets. VSM analysis results showed that rGO/Fe3O4/ZnSe nanocomposites had good superparamagnetic behavior with magnetization saturation (Ms) at about 35.2 emu/g. The double layer capacitance (Cdl) and activated surface area of rGO/Fe3O4/ZnSe nanocomposite were measured at about 39 mF.cm−2 and 0.097 cm2, respectively.

Iron powder in-situ catalytic pyrolysis on coated wooden board: Kinetic, products, and recovery

Catalytic pyrolysis is a promising method for the resource utilization of wooden waste, and in-situ catalysis enhances the process and reduces treatment costs. The selection of catalysts is crucial, as their catalytic effect and service life directly impact treatment effectiveness and economic benefits. In this study, iron powder was utilized to examine its potential in in-situ catalytic pyrolysis of coated wooden boards. The results showed that some of the iron powder could compete for oxygen from lignin/ hemicellulose during the early pyrolysis stage, resulting in the formation of FeO and a decrease in CO2. The formed FeO then promoted cellulose decomposition, reducing the pyrolysis activation energy by 26% ∼ 48%. Despite the addition of iron powder, no obvious impact was observed on the distribution of product yields. However, there are differences in the specific composition: the gas products showed a decrease of CO2 by 26% and CH4 by 13%, while the bio-oil showed an increase of phenol by 8%. This revealed that the iron powder primarily changed the energy barrier of the pyrolysis reaction. There was magnetic separation followed by particle size screening for the recovery of solid products. After separation, the recovery rate of iron powder was determined to be only 65.39%. Two kinds of char particles appeared in the separated products: magnetic (M3) and non-magnetic (NM). Approximately 44.45% of total Fe (from Fe powder and coating materials) contents and 73.62% of total Ti (main metal in the primary coating) were found in M3, while only 1.32% and 10.90% in NM, respectively. Interestingly, the distribution of elements Zn, Ba, and Mg was found to be opposite to that of Fe, which mainly distributed in NM and M2. It might be attributed to the primary coating on the M3 surface, which likely to help facilitated the adsorption of iron particles according to the combination of SEM/EDS and ICP-MS results. The adsorption competition effect of Fe and other metals resulted in significant differences in the distribution of metals on several char particles.

Influence of temperature on corrosion behavior of N80 Steel in multiple thermal fluid environment

During offshore oil production, O2 could be introduced into the multiple thermal fluid, and the temperature of the wellbore can reach up to 200°C, which may result severe corrosion of tubing. However, the corrosion mechanism of downhole pipes in such aggressive environment remains unclear in the high-temperature and high-pressure CO2-O2-H2O mixed environment. Herein, we investigated the corrosion behaviour of N80 steel with different temperatures in CO2-O2-H2O environment. The influence of temperature on composition and structure of the corrosion product film of N80 steel was characterized by scanning electron microscope, energy-dispersive spectroscopy and X-ray diffraction. The results show that the corrosion rates of N80 steel performed a downward trend with the increase of the temperature, but it increased slightly at 180°C. The corrosion rate of N80 steel was up to 1.6 mm/y at 60°C, owing to the damage to corrosion product film by O2 and reduced its protection at lower temperature. As the temperature increased, the formation of Fe3O4 enhanced the protection of the inner corrosion product film, thereby greatly reducing the corrosion rate. However, the product of (FeCa)CO3 in the corrosion film completely lost its protection at 180°C, and the corrosion rate increased slightly to 0.84 mm/y. With the temperature increased to 240°C the corrosion rate of N80 steel reduced to 0.24 mm/y on account of the formation of dense and complete Fe3O4.

Study on the Influence of CaO on the Electrochemical Reduction of Fe2O3 in NaCl-CaCl2 Molten Salt.

The presence of calcium-containing molten salts in the electrolysis of oxides for metal production can lead to the formation of CaO and, subsequently, the generation of intermediate products, affecting the reduction of metals. To investigate the impact of CaO on the reduction process, experiments were conducted using a Fe2O3-CaO cathode and a graphite anode in a NaCl-CaCl2 molten salt electrolyte at 800 °C. The electrochemical reduction kinetics of the intermediate product Ca2Fe2O5 were studied using cyclic voltammetry and I-t curve analysis. The phase composition and morphology of the electrolysis products were analyzed using XRD, SEM-EDS, and XPS. The experimental results demonstrate that upon addition of CaO to the Fe2O3 cathode, Ca2Fe2O5 is formed instantly in the molten salt upon the application of an electrical current. Research conducted at different voltages, combined with electrochemical analysis, indicates that the reduction steps of Ca2Fe2O5 in the NaCl-CaCl2 molten salt are as follows: Ca2Fe2O5 ⟶ Fe3O4 ⟶ FeO ⟶ Fe. The presence of CaO accelerates the electrochemical reduction rate, promoting the formation of Fe. At 0.6 V and after 600 min of electrolysis, all of the Ca2Fe2O5 is converted into Fe, coexisting with CaCO3. With an increase in the electrolysis voltage, the electrolysis product Fe particles visibly grow larger, exhibiting pronounced agglomeration effects. Under the conditions of a 1 V voltage, a study was conducted to investigate the influence of time on the reduction process of Ca2Fe2O5. Gradually, it resulted in the formation of CaFe3O5, CaFe5O7, FeO, and metallic Fe. With an increased driving force, one gram of Fe2O3-CaO mixed oxide can completely turn into metal Fe by electrolysis for 300 min.

Structural, optical, photocatalytic, and magnetic properties of new hydrothermal synthesized Cd1–xSnxFe2O4 nanocomposites

Herein, structural, surface area, optical, photocatalytic, and magnetic properties of a new Cd1–xSnxFe2O4 nanocomposites (1 ≥ x ≥ 0), synthesized by the hydrothermal approach were investigated. The nanocomposite formation is confirmed by X-ray diffraction analysis (XRD), Transmission electron microscopes (TEM), Fourier transform infrared (FTIR), Inductively coupled plasma (ICP), and Energy dispersive X-ray (EDX) analyses. The XRD findings reveal the formation of Fe2O3 at x = 0, 0.2, 0.4, and 1, while the Fe3O4 phase at x = 1 besides the spinel CdFe2O4 phase for x = 0.6 and 0.8, and rutile SnO2 phase for x ≥ 0.8. The crystal structure, e.g., lattice parameters, bond length, cell volume, theoretical density, crystallite size, dislocation density, and microstrain are remarkably influenced by elemental ratios. The average crystallite size of composites declined to 15.2 ± 4 nm as x increased to 0.4, then grew to 40.5 ± 4 nm at x = 0.6, and then decreased to 21 ± 10 nm at x = 1. The particle morphologies were deduced, and crystal structures were confirmed by analyzing field-emission scanning electron microscope (FE-SEM), and TEM micrographs. FTIR confirmed the presence of metal oxide bands for all nanocomposites. The surface area was calculated via the Brunauer–Emmett–Teller (BET) and Barrett-Joyner-Halenda (BJH) theories to the N2 adsorption–desorption isotherm and equals 10.5, 20.3, 17.1, and 25.2 m2/g at x = 0, 0.4, 0.6, and 1, respectively. The magnetic properties of the Cd1–xSnxFe2O4 nanocomposites were studied by vibrating-sample magnetometry (VSM) technique, which displayed their ferromagnetic behaviors. The addition of Sn2+ into the composite improved the magnetic saturation from 0.42 to 34.7 emu/g by changing x from 0 to 0.4 then was reduced to 5.9 emu/g at x = 1 which well matched with the behavior of total pore volume. Furthermore, the indirect optical band gap (Egin) was increased, e.g., Egin equals 1.22, 1.82, 1.88, and 2.08 eV for x = 0, 0.4, 0.6, and 1, respectively. Methylene blue photocatalytic performance was investigated, and the maximumdegradation efficiency of 44.33 %was detected using Cd1–xSnxFe2O4 at x = 0.8 under UV–visible irradiation for 160 min.

Mesoscale numerical simulation of the multiple step reaction in hydrogen reduction of iron oxides

This work designed a mesoscale method of multi-step reduction of Fe2O3 with H2 based on Lattice Gas Cellular Automata (LGCA). Particles in the LGCA were marked to distinguish all the reactants, intermediates, products, and inert. A self-organized evolutionary mechanism is designed. The hydrogen reduction of Fe2O3 in the temperature range of 460–550 °C and 650–800 °C was simulated. Results show that the intermediate product Fe3O4 was found in both conditions, and its mass fraction quickly reach a peak at ∼0.8 and gradually decrease thereafter. An “induction period” can be identified in the initial stage of the reaction at 650–800 °C, where the reduction rate is slow due to the hindered formation of FeO. The porosity inside the Fe2O3 particles increases continuously through the reduction process, resulting in significant changes in the flow field around the particles. Consequently, the wake vortex gradually decreases and disappears eventually.

Characterization of Magnetic Biochar Modified Using the One-Step and Electrochemical Methods and Its Impact on Phosphate Adsorption.

The properties and phosphate adsorption capability of the one-step method and electrochemical method in modifying peanut shell biochar have been determined. The one-step method deposits MgO and Fe3O4 onto biochar through chemical impregnation and regularly affects the functional groups and magnetic separation of biochar, thereby enhancing its ability to adsorb phosphate. In contrast, the electrochemical method is not favorable for modifying functional groups of biochar but can promote phosphate adsorption because of the formation of MgFe2O4 and Fe3O4 using electrolysis. The adsorption isotherm and kinetics data suggest that adsorption is monolayer onto a homogeneous surface and phosphate adsorption could be controlled by chemical processes. Biochar with the addition of both Fe2+ and Mg2+ shows better phosphate adsorption capability than those with barely any Fe2+ additions. It was concluded that the one-step method is a better modification method than the electrochemical method for enhancing the phosphate adsorption capability of biochars.

Green synthesis of Iron oxide and Iron dioxide nanoparticles using Euphorbia tirucalli: characterization and antiproliferative evaluation against three breast cancer cell lines

Researchers have become increasingly interested in nanoparticles made from plants because of their stability and large surface area. In the current study, iron oxide and iron dioxide nanoparticles were synthesized using aerial parts of the E. tirucalli as a reducing agent. The nanoparticles were analyzed using various techniques, including Ultraviolet-visible spectroscopy, Fourier Transform Infrared spectroscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, X-ray energy dispersive spectroscopy, Scanning electron Microscopy, and Transmission Electron Microscopy. The nanoparticles were then investigated for their antiproliferative effect against MCF-7, SK-BR-3, MDA-MB231, and Vero cell lines. The results confirmed the formation of FeO and FeO2 nanoparticles by color change and a UV absorbance peak between 220–390 nm. EDS analysis showed traces of Fe and O, while TEM confirmed the nanoparticle size of 100 nm. FTIR showed a peak at 514 nm. The FeO-RT NPs demonstrated over 80% antiproliferative activity against the MCF-7 cell line at a concentration of 10 μg/mL. while doxorubicin, FeO-RT NPs, and DCM extract showed similar activity against the MDA-MB231 cell line at 10 and 1 g/mL concentrations. However, Vero and SK-BR-3 cell lines showed decreased antiproliferative activity. This study highlights the environmentally friendly use and safe application of iron oxide NPs in cancer therapy.

Evaluation of iron containing biochar composites prepared by different preparation methods for H2O2 sensing

BackgroundThe procedures employed to prepare the ferrous biochar samples, the iron salts utilized, and their quantities have an effect on the surface characteristics of the material and the types of iron that will develop on the surface. MethodsIron containing biochar (Fe-BC) samples were prepared using three different preparation methods: Precipitation, Impregnation (IP) and Solid-state (SS). The iron content of the biochar (BC) was varied in a range from 6.5 to 21.0 wt. % by using a SS method that mechanically mixed FeCl3 and hazelnut shell (HS) in solid form. Significant FindingsThe XRD, XPS and FT-IR results showed that the magnetite particles (Fe3O4) were mainly formed on the surface of all samples, but their content was strongly dependent on the preparation method and the amount of iron. Additionally, the formation of Fe2O3, Fe2C, FeCO3, and FeOOH species on the surface was determined. The highest surface area and microporosity were obtained for the Fe-BC sample prepared by IP (Fe-BC-IP):850 m2/g and 0.28 cm3/g, respectively. A novel and fast electrochemical sensing platform for the detection of H2O2 with a broad linear range (0.5-10 mM) and high sensitivity (621 µA mM−1 cm−2) was fabricated. The findings demonstrate that the non-enzymatic BC-IP sensor is a useful alternative for measuring H2O2.

Fe3O4 nanoparticles anchored on carbon nanotubes as high-performance anodes for asymmetric supercapacitors

Fe3O4/CNT composites are synthesized with ethylene glycol as solvent by a one-step solvothermal method and used as anode materials for asymmetric supercapacitors (ASC). An appropriate amount of water in ethylene glycol can accelerate the formation of Fe3O4 and reduce the average size of Fe3O4 to around 20 nm. However, spherical Fe3O4 particles larger than 100 nm will form in pure ethylene glycol for long reaction time. The Fe3O4/CNT composite with small Fe3O4 nanoparticles exhibits a high specific surface area, promoted electron transfer ability, as well as a high utilization rate of active materials. The optimized electrode shows a high specific capacity of 689 C g−1 at 1 A g−1, and remains 443 C g−1 at 10 A g−1. The inferior long-term cycling stability is due to the phase transition of Fe3O4 and a reductive effect to form metallic Fe. An ASC using Fe3O4/CNT and NiCoO2/C composites as anode and cathode, respectively, delivers a high energy density of 58.1 Wh kg−1 at a power density of 1007 W kg−1 in a voltage window of 1.67 V and has a capacity retention of 63% after 5000 cycles. The self-discharge behavior of the ASC is also investigated.

High-precision in situ 3D ultrasonic imaging of localized corrosion-induced material morphological changes

We present an ultrasonic research technique that can carry out in situ, direct monitoring of the 3D morphologies of corrosion substrates. The technique has a customizable lateral resolution, an ultra-high axial resolution of 100 nm, and an experimentally proven measurement accuracy. In using the technique to monitor the localized corrosion processes of carbon steel under constant DCs, it was observed that during each of the experiments conducted in alkaline environments, iron dissolution accelerated for a certain period of time and then slowed down. Based on the various features of the ultrasonic signals acquired and the XRD spectra of the corrosion products obtained, it was deduced that an increase in iron dissolution rate as such was accompanied by the depositing of solid corrosion products onto the substrate used and driven by the formation of Fe3O4, which consumed electrons. After a while, the corrosion product layer collapsed and the formation of Fe3O4 was halted.

Interaction between silty sand and temperature towards corrosion behavior of carbon steel in CO2 environment

The interaction between silty sand and temperature towards corrosion of carbon steel in CO2 environment is investigated. The effect of silty sand is more complicated, while the effect of temperature is more remarkable. High temperature causes a more protective corrosion products layer. Silty sand physically adsorbs on the surface and embeds in the porous Fe3C layer at 40 ℃ to slightly reduce corrosion. At 80 ℃, silty sand delays FeCO3 precipitation and significantly increases the porosity of corrosion products layer, thus promoting corrosion. At 120 ℃, silty sand increases the porosity and hinders the formation of Fe3O4 to accelerate corrosion.

Identification of the Fe[formula omitted]O[formula omitted]–Fe[formula omitted]O[formula omitted] reaction in liquid lead–bismuth eutectic

Liquid lead–bismuth eutectic (LBE) is a heavy metal alloy with great potential as a coolant and spallation target material for Generation IV nuclear reactors. For LBE technology to be widely accepted as reliable, a comprehensive understanding of LBE coolant chemistry is crucial. Specifically, precise determination of chemical interactions between corrosion products and dissolved oxygen in LBE is essential. For that purpose, the thermal cycling method is used in the present research, in which a well-controlled batch of LBE is repeatedly cooled while a potentiometric oxygen sensor monitors the dissolved oxygen concentration.According to the literature, magnetite (Fe3O4) is confirmed to be an important oxide to describe oxygen–iron interaction in LBE. However, thermal cycling experiments indicate the presence of another oxide, besides Fe3O4, participating in LBE bulk chemistry under conditions relevant for LBE-cooled reactors (200 °C–400 °C, 10−8 wt.%–10−5 wt.% dissolved oxygen concentration). By varying iron impurity content, nickel impurity content and cooling rate in the experiments, the oxide has been identified as hematite (Fe2O3). Thermodynamic equilibrium calculations show that Fe2O3 formation through the reaction of Fe3O4 with dissolved oxygen can explain the observed oxygen trends. As Fe2O3 could form during LBE cooling, an oxygen control strategy should take into account additional oxygen consumption in the reactor cold leg.

Atomistic simulation on the nano-scale oxidation of Fe-Cr alloy surfaces and the diffusion behavior of oxygen

The oxidation of Fe-Cr alloy surfaces was performed by reactive molecular dynamics (MD) simulations. The results shown that the addition of Cr caused a slow internal diffusion of oxygen with a thinner oxide layer in the Fe-Cr alloy, indicating improved oxidation resistance. Furthermore, the achievement of the saturation point in the diffusion flux of oxygen in Fe-Cr alloy was closely linked to the oxide structure, the formation of FeO may inhibit further oxidation by preventing more oxygen ions from reaching the unoxidized interior. Therefore, the evolution of oxide structure played a crucial role in improving the oxidation resistance of Fe-Cr alloys.

Solid-State Schikorr Reaction from Ferrous Chloride to Magnetite with Hydrogen Evolution as the Kinetic Bottleneck.

The selective formation of meta-stable Fe3O4 from ferrous sources by suppressing its oxidative conversion to the most stable hematite (α-Fe2O3) is challenging under oxidative conditions for solid-state synthesis. In this work, we investigated the conversion of iron(II) chloride (FeCl2) to magnetite (Fe3O4) under inert atmosphere in the presence of steam, and the obtained oxides were analyzed by atomic-resolution TEM, 57Fe Mössbauer spectroscopy, and the Verwey transition temperature (Tv). The reaction proceeded in two steps, with H2O as the oxide source in the initial step and as an oxidant in the second step. The initial hydrolysis occurred at temperatures higher than 120 °C to release gaseous HCl, via substituting lattice chloride Cl- with oxide O2-, to give iron oxide intermediates. In the first step, the construction of the intermediate oxides was not topotactic. The second step as a kinetic bottleneck occurred at temperatures higher than 350 °C to generate gaseous H2 through the oxidation of FeII by H+. A substantially large kinetic isotope effect (KIE) was observed for the second step at 500 °C, and this indicates the rate-determining step is the hydrogen evolution. Quantitative analysis of evolved H2 revealed that full conversion of ferrous chloride to magnetite at 500 °C was followed by additional oxidation of the outer sphere of magnetite to give a Fe2O3 phase, as supported by X-ray photoelectron spectroscopy (XPS), and the outer phase confined the conductive magnetite phase within the insulating layers, enabling kinetic control of magnetite synthesis. As such, the reaction stopped at meta-stable magnetite with an excellent saturation magnetization (σs) of 86 emu g-1 and Tv > 120 K without affording the thermodynamically stable α-Fe2O3 as the major final product. The study also discusses the influence of parameters such as reaction temperature, initial grain size of FeCl2, the extent of hydration, and partial pressure of H2O.

Fusion-Assisted Hydrothermal Synthesis of Technogenic-Waste-Derived Zeolites and Nanocomposites: Synthesis, Characterization, and Mercury (II) Adsorption.

This study presents the synthesis of zeolites derived from coal fly ash (CFA) using the fusion-assisted alkaline hydrothermal method. The zeolites were synthesized by combining CFA and NaOH at a molar ratio of 1:1.2 under fusion temperatures of 500, 600, and 700 °C. Subsequently, the obtained zeolites were subjected to further modifications through the incorporation of magnetic (Fe3O4) and silver (Ag0) nanoparticles (NPs). The Fe3O4 NPs were introduced through co-precipitation of Fe(NO3)2 and FeCl3 at a molar ratio of 1:1, followed by thermal curing at 120 °C. On the other hand, the Ag0 NPs were incorporated via ion exchange of Na+ with Ag+ and subsequent reduction using NaBH4. The synthesized porous materials exhibited the formation of zeolites, specifically analcime and sodalite, as confirmed by X-ray diffraction (XRD) analysis. Additionally, the presence of Fe3O4 and Ag0 NPs was also confirmed by XRD analysis. The elemental composition analysis of the synthesized nanocomposites further validated the successful formation of Fe3O4 and Ag0 NPs. Nitrogen porosimetric analysis revealed the formation of a microporous structure, with the BET surface area of the zeolites and nanocomposites ranging from 48.6 to 128.7 m2/g and pore sizes ranging from 0.6 to 4.8 nm. The porosimetric characteristics of the zeolites exhibited noticeable changes after the modification process, which can be attributed to the impregnation of Fe3O4 and Ag0 NPs. The findings of this research demonstrate the effectiveness of the fusion-assisted method in producing synthetic zeolites and nanocomposites derived from CFA. The resulting composites were evaluated for their potential application in the removal of mercury ions from aqueous solutions. Among the samples tested, the composite containing Ag0 NPs exhibited the highest adsorption capacity, reaching 107.4 mg of Hg2+ per gram of composite. The composites modified with Fe3O4 NPs and Ag/Fe3O4 nanocomposites displayed adsorption capacities of 68.4 mg/g and 71.4 mg/g, respectively.

Degradation of Chloroform by Zerovalent Iron: Effects of Mechanochemical Sulfidation and Nitridation on the Kinetics and Mechanism.

Chloroform (CF) is a widely used chemical reagent and disinfectant and a probable human carcinogen. The extensive literature on halocarbon reduction with zerovalent iron (ZVI) shows that transformation of CF is slow, even with nano, bimetallic, sulfidated, and other modified forms of ZVI. In this study, an alternative method of ZVI modification─involving simultaneous sulfidation and nitridation through mechanochemical ball milling─was developed and shown to give improved degradation of CF (i.e., higher degradation rate and inhibited H2 evolution reaction). The composite material (denoted as S-N(C)-ZVI) gave synergistic effects of nitridation and sulfidation on CF degradation. A complete chemical reaction network (CRN) analysis of CF degradation suggests that O-nucleophile-mediated transformation pathways may be the main route for the formation of the terminal nonchlorinated products (formate, CO, and glycolic polymers) that have been used to explain the undetected products needed for mass balance. Material characterizations of the ZVI recovered after batch experiments showed that sulfidation and nitridation promoted the formation of Fe3O4 on the S-N(C)-ZVI particles, and the effect of aging on CF degradation rates was minor for S-N(C)-ZVI. The synergistic benefits of sulfidation and nitridation on CF degradation were also observed in experiments performed with groundwater.