Search

Fe 2 O 3 -supported activated carbon felts (Fe-ACFTs) were prepared by impregnating the felts consisted of activated carbon fibers (ACFs) with either polyester fibers (PS-A20) or polyethylene pulp (PE-W15) in Fe(III) nitrate solution and calcination at 250 °C for 1 h. The prepared Fe-ACFTs with 31–35 wt% Fe were characterized by N 2 -adsorption, scanning electron microscopy, and X-ray diffraction. The Fe-ACFT(PS-A20) samples with 5–31 wt% Fe were microporous with specific surface areas ( S BET ) ranging from 750 to 150 m 2 /g, whereas the Fe-ACFT(PE-W15) samples with 2–35 wt% Fe were mesoporous with S BET ranging from 830 to 320 m 2 /g. The deposition of iron oxide resulted in a decrease in the S BET and methylene blue (MB) adsorption capacity while increasing the photodegradation of MB. The optimum MB degradation conditions included 0.98 mM oxalic acid, pH = 3, 0.02–0.05 mM MB, and 100 mg/L photocatalyst. The negative impact of MB desorption during the photodegradation reaction was more pronounced for mesoporous PE-W15 samples and can be neglected by adding oxalic acid in cyclic experiments. Almost complete and simultaneous mineralization of oxalate and MB was achieved by the combined heterogeneous-homogeneous photocatalytic processes. The leached Fe ions in aqueous solution [Fe 3+ ] f were measured after 60 min for every cycle and found to be about 2 ppm in all four successive cycles. The developed photocatalytic materials have shown good performance even at low content of iron oxide (2–5 wt% Fe-ACFT). Moreover, it is easy to re-impregnate the ACF when the content of iron oxide is reduced during the cyclic process. Thus, low leaching of Fe ions and possibility of cyclic usage are the advantages of the photocatalytic materials developed in this study. [ABSTRACT FROM AUTHOR]

In-situ Raman spectroscopy was performed on 1010 steel coatings thermally sprayed on an Al-Si alloy on A 380 (Al-9.0% Si) cylinder bore and subjected to reciprocating sliding against various coated rings to investigate the progression of iron oxide formation during sliding. The coatings evaluated for the top compression ring (TCR) included diamond-like carbon (DLC) and chromium nitride (CrN). The reciprocating tests were conducted under unlubricated and boundary lubricated conditions. During unlubricated sliding, a running-in period was observed with increasing coefficient of friction (COF) values which corresponded to the conversion of the initial FeO, present in the as-deposited coating, to Fe 3 O 4 and then to Fe 2 O 3 as identified by changes in Raman spectra obtained at short intervals during the test. Once a Fe 2 O 3 layer was formed, a steady state regime was obtained with a COF of 0.4 that was accompanied by the adhesion of the oxide debris generated during sliding to the counterfaces. The DLC coated TCR provided low steady state COF (0.18) and volumetric wear of 1010 steel, with negligible debris formation. Boundary lubricated sliding tests, with an initial period of unlubricated sliding, resulted in low steady state COF value of 0.10 for DLC and 0.16 for CrN. The low friction and wear of 1010 coatings observed during boundary lubricated sliding against DLC coated TCR was due to a composite tribolayer consisting of an amorphous carbon layer on top of an oil residue layer that was formed on the sliding surfaces. [ABSTRACT FROM AUTHOR]

Chemical reduction behaviour of 3% chromium doped (Cr–Fe 2 O 3 ) and undoped iron oxides (Fe 2 O 3 ) were investigated by using temperature programmed reduction (TPR). The reduced phases were characterized by X-ray diffraction spectroscopy (XRD). The reduction processes were achieved with 10% H 2 in nitrogen (%, v/v), 10% and 20% of carbon monoxide (CO) in nitrogen (%, v/v). In hydrogen atmosphere, the TPR results indicate that the reduction of Cr–Fe 2 O 3 and Fe 2 O 3 proceed in three steps (Fe 2 O 3 → Fe 3 O 4 → FeO → Fe) with Fe 3 O 4 and FeO as intermediate states. A complete reduction to metallic iron for both samples occurred at 900 °C. As for CO reductant, the profiles show the reduction of Fe 2 O 3 also proceeded in three steps with a complete reduction occurs at 900 °C in 10% CO with no sign of carbide formation. Nevertheless, a 20% CO was able to reduce the completely at lower temperature at 700 °C and there is a formation of iron carbide at 500 °C but the carbide disappeared as the reduction temperature increase. Meanwhile in 10% CO atmosphere, Cr–Fe 2 O 3 shows a better reducibility compared to Fe 2 O 3 with a complete reduction at 700 °C, which is 200 °C lower than Fe 2 O 3 . A Cr dopant in the Fe 2 O 3 can lead to formation of various forms of iron carbides such as F 2 C, Fe 5 C 2 , Fe 23 C 6 and Fe 3 C as the CO concentration was increased to 20%. The transformation profile of iron phases during carburization follows the following forms, Fe 2 O 3 → Fe 3 O 4 → iron carbides (Fe x C). The XRD pattern shows the diffraction peaks of Cr–Fe 2 O 3 are more intense with improved crystallinity for the characteristic peaks of Fe 2 O 3 compare to undoped Fe 2 O 3 . No visible sign of chromium particles peaks in the XRD spectrum that indicates the Cr particles loaded onto the iron oxide are well dispersed. The uniform dispersion with no sign of sintering effects of the Cr dopant on the Fe 2 O 3 was confirmed by FESEM. The study shows that Cr dopant gives a better reducibility of iron oxide but promotes the formation of carbides in an excess CO concentration. [ABSTRACT FROM AUTHOR]

Herein, we report a non-enzymatic glucose sensor field-effect transistor (FET) based on vertically-oriented zinc oxide nanorods modified with iron oxide (Fe 2 O 3 -ZNRs). Compared with ZnO-based non-enzymatic glucose sensors, which show poor sensing performances, modification of ZnO with Fe 2 O 3 dramatically enhances the sensing behavior of the fabricated non-enzymatic FET glucose sensor due to the excellent electrocatalytic nature of Fe 2 O 3 . The fabricated non-enzymatic FET sensor showed excellent catalytic activity for glucose detection under optimized conditions with a linear range up to 18 mM, detection limits down to ~ 12 μM, excellent selectivity, good reproducibility and long-term stability. Moreover, the fabricated FET sensor detected glucose in freshly drawn mouse whole blood and serum samples. The developed FET sensor has practical applications in real samples and the solution-based synthesis process is cost effective. [ABSTRACT FROM AUTHOR]

Magnetic porous iron oxide monoliths were obtained using a polyethylene oxide-mediated sol-gel process. The hierarchical porous structure in the xerogel monolith of FeO(C 3 H 7 O 3 ) 0.69 (OH) 0.31 ·0.42(HCl)·1.08(polyacrylamide) was preserved with pore diameters of 1–4 μm in the oxide monoliths after calcinations in air at 350 °C for various duration. The iron oxide monolith exhibited ferromagnetic behavior in magnetization vs. magnetic field curve after firing at 350 °C for 6 h. Both magnetization and magnetic coercivity can be optimized by changing the calcinations condition to obtain the iron oxide monoliths. The ferromagnetic iron oxide monolith will be much more useful in continuous separation than magnetic particles in a wide range of separation especially in biotechnology industry. [ABSTRACT FROM AUTHOR]

Fe 2 O 3 and Pd are successively deposited on an activated carbon support by atomic layer deposition (ALD), producing a large surface area catalyst containing varied loadings of Pd and Fe 2 O 3 . Various structural characterization techniques reveal that the Fe 2 O 3 species forms a uniformly distributed amorphous layer on which Pd nanoparticles are anchored. In the hydrodechlorination of 1,4-dichlorobenzene ALD Pd/Fe 2 O 3 /AC catalysts outperform a series of control samples including impregnated Pd-Fe 2 O 3 -AC and mixtures of ALD Pd/AC and Fe 2 O 3 /AC. The improved catalytic performance is mostly attributed to the anti-poisoning effect of Fe 2 O 3 located in close vicinity to Pd. [ABSTRACT FROM AUTHOR]

High-surface-area iron oxides were prepared by Atomic Layer Deposition (ALD) on 130-m 2 /g γ-Al 2 O 3 for use as a catalyst support. Measurements of the sample mass, surface area, and pore-size distribution as a function of the number of ferrocene-O 2 ALD cycles at 623 K suggested that the iron oxide grew as a dense, conformal film with a growth rate similar to 0.016-nm per cycle. While films with 20 ALD cycles (20Fe 2 O 3 -Al 2 O 3 , 0.25 g Fe 2 O 3 /g Al 2 O 3 ) were difficult to distinguish by HAADF STEM, EDS mapping indicated the Al 2 O 3 was uniformly coated. Raman Spectroscopy showed the films were in the form of Fe 2 O 3 ; but XRD measurements on samples with as many as 100 ALD cycles (100Fe 2 O 3 -Al 2 O 3 , 0.84 g Fe 2 O 3 /g Al 2 O 3 ) showed no evidence for crystalline iron-oxide phases, even after calcination at 1073 K. Specific rates for the water-gas-shift (WGS) reaction on the ALD-coated samples were significantly lower than those on bulk Fe 2 O 3 . However, addition of 1 wt.% Pd to Fe 2 O 3 /Al 2 O 3 supports prepared by ALD exhibited specific rates that were much higher than that observed when 1 wt.% Pd was added to Fe 2 O 3 /Al 2 O 3 prepared by conventional impregnation of Fe salts, suggesting more uniform contact between the Pd and FeO x phases on samples prepared by ALD. [ABSTRACT FROM AUTHOR]

Iron foams with aligned, lamellar channels were created by directionally freeze-casting slurries of water and Fe 2 O 3 nanopowders, sublimating the ice, and reducing and sintering under hydrogen the powders accumulated in the interdendritic spaces. Foam porosity decreases from 85 to 50% with Fe 2 O 3 slurry fractions increasing from 14 to 23 vol.%. For foams created from 18.5 vol.% Fe 2 O 3 slurries, with increasing sintering temperature from 900 to 1100 °C, a decrease in porosity from 71 to 61% and an increase in unidirectional compression strength from 8 to 20 MPa are observed. [ABSTRACT FROM AUTHOR]

A novel fabrication of Fe 3 O 4 nanotubes (NT) on FTO as nanoelectrode for enzyme-free glucose-sensing application is described. The structural transformation of Fe 3 O 4 NT occurs on, first, immersion of a ZnO nanowire into an aqueous solution of FeCl 3 , and, subsequently, annealing in air and in vacuum. A tube-like morphology, with length several micrometres and diameter ~ 100 nm, was observed with a scanning electron microscope. Those NT were confirmed to possess Fe 3 O 4 in a cubic phase upon structural and composition analysis with X-ray diffraction, and Raman and X-ray photoelectron spectra. The directly grown Fe 3 O 4 NT array is mechanically stable and provides an excellent electrochemical sensing platform. Showing excellent electrocatalytic response to glucose with detection limit 0.1 μM, rapid response and great sensitivity with 3 ranges of linear relation for the amperometric detection of glucose, this array electrode is readily applicable to other analytes and has great prospective applications in electrochemical detection. [ABSTRACT FROM AUTHOR]

Nanoparticulated iron oxide-hydroxide samples are synthetized in supercritical water in continuous regime. Freshly prepared iron(II) acetate solutions are used as precursors and experiments at different flow rates and reactor temperatures are carried out. Samples composition is determined by thermogravimetric and energy loss spectroscopy. The obtained powdered samples are structurally characterized through Rietveld refinements of X-ray diffraction data. They mainly consist of FeO 1.5−z spinel-type phases, though minority oxyhydroxide and hematite phases are obtained at low temperatures and total flow rates. Analysis by electron microscopy reveals mean particles sizes around 30 nm and roughly spherical morphology in most cases. The electrochemical response, cycling performance and Coulombic efficiency are evaluated from discharge-charge and cycling experiments at different current densities. The obtained response seems to depend on the presence or absence of oxyhydroxide phases and on both microstructural homogeneity at nanoscale and relative concentration of supercritical water at the mixing point. The 7-3-200 electrode sample shows superior rate capability, with capacity values higher than graphite theoretical one, even at high rates (500 Ah kg −1 at 2C after 100 cycles). Besides, the capacity values are restored when returning to low rates, reaching 1200 Ah kg −1 at C/5 and 800 Ah kg −1 at C/2. [ABSTRACT FROM AUTHOR]

Shut-down or reduced treated water supply of a seawater reverse osmosis (SWRO) plant due to membrane fouling during a red tide event is currently an important issue in regions where red tide frequently occurs. Algal organic matter (AOM) released by algae through metabolic activity is known as a major membrane foulant and the primary cause of the suspension of SWRO plants. In this study, iron oxide was utilized to develop an AOM removal process in seawater since activated carbon and advanced oxidation process (AOP) have limited removal efficiencies due to the high ionic strength of the seawater. Dynamic membrane filtration was applied as an iron oxide application method because additional process is not required for temporary operation during only algal bloom. The results showed that the dissolved organic carbon (DOC) removal efficiencies of the iron oxide were improved at high ionic strength compared to organics removal in fresh water. Although only a partial adsorption rate (below 50%) was achieved using iron oxide, significant reduction of the ultrafiltration (UF) membrane fouling was observed through the continuous operation of dynamic membrane filtration since relatively high molecular weight faction of organics was more readily adsorbed in the oxide surface. Given the continuous lab-scale experimental results and economic aspect, dynamic membrane filtration using powdered iron oxide can be a potential option as an emergency plan during a red tide event. [ABSTRACT FROM AUTHOR]

Magnetic iron oxide nanoparticles with a narrow size distribution were synthesized by hydrothermally treating suspensions of iron oxide nanoparticles. Ricinoleic-acid-coated magnetic nanoparticles were co-precipitated at room temperature from an aqueous solution of Fe 2+ /Fe 3+ cations by the addition of a base. The presence of the ricinoleic acid on the nanoparticles' surfaces strongly suppressed their growth under the hydrothermal conditions. Because of the strong dependency of the rate of particle growth on their size, the size distribution significantly narrowed during the hydrothermal treatment. The size of the nanoparticles was successfully controlled by the temperature of the synthesis and the amount of ricinoleic acid present in the reaction mixture to between 9 and 30 nm. The presence of the ricinoleic acid on nanoparticles' surfaces enabled the preparation of colloidal suspensions in even moderately polar organic liquids. Measurements of the magnetic properties revealed that the nanoparticles smaller than 14 nm exhibited superparamagnetic behavior and nanoparticles larger than 15 nm displayed single-domain ferrimagnetic behavior. The nanoparticles exhibited large values of saturation magnetization of up to 90 emu/g. The strong dependence of the nanoparticles' specific power losses when subjected to an alternating magnetic field on their average size and frequency was demonstrated. The ferrimagnetic nanoparticles showed much higher power losses than the superparamagnetic nanoparticles. [ABSTRACT FROM AUTHOR]

Magnetic properties of Fe 2 O 3 /SiO 2 samples were studied after being produced by sol-gel synthesis and formation of ε-Fe 2 O 3 polymorph. Samples were thermally treated, using different annealing temperatures and annealing times. The size and morphological characteristics of the iron oxide nanoparticles were examined using a TEM microscope. We used the “ellipticity of shapes”, which is a measure of how much the shape of a nanoparticle differs from a perfect ellipse, in order to quantitatively describe morphological properties of nanoparticles. Coercivity measurements were used to identify and monitor the formation of the epsilon-iron oxide phase during the thermal treatments (annealing). Coercivity values were in the range from 1.2 to 15.4 kOe, which is in accordance with previous experience regarding the existence of ε-Fe 2 O 3 . We have determined the optimal formation conditions for the ε-Fe 2 O 3 polymorph (t=1050 °C for 7 h, H C =15.4 kOe), as well as the narrow temperature interval (1050–1060 °C) in which the polymorph abruptly vanished (H C =2300 Oe), on the basis of results of the magnetic properties. The threshold temperature for the ε-Fe 2 O 3 phase transformation was measured as 1060 °C. We found that different annealing temperatures and annealing times significantly affected magnetic properties of the examined samples. [ABSTRACT FROM AUTHOR]

The development of innovative, safe and non-photocatalytic sunscreens is urgently needed, as it is essential to have sunscreen filters offering appropriate UV protection without damaging the environment and/or generating free radicals when in contact with the skin. Hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp) when substituted with iron has UV protection properties and is not photocatalytic; HAp was used to make a sunscreen filter by treating cod fish bones in an iron-containing solution, and then calcining them at 700 °C. Here we present a systematic and advanced study on this material, to obtain a sunscreen with improved UV absorbing properties. Bones were treated with three different iron salts - Fe(II) chloride, Fe(II) lactate and Fe(III) nitrate - under various pH conditions. Results showed that Fe(II) chloride in basic pH led to the most effective iron inclusion. High energy ball milling or ultrasound were investigated to increase surface area and corresponding UV absorption; high energy ball milling treatment led to the best optical properties. The optimum powders were used to formulate UV protection creams, which showed Sun Protection Factor (SPF) values significantly superior to the control cream (up to 4.1). Moreover the critical wavelength (λ crit ) was > 370 nm (388–389 nm) and UVA/UVB ratios were very close to 1. With these properties these sunscreens can be classified as broad UV protectors. Results also showed that combining these powders with other sunscreens (i.e. titanium dioxide), a synergic effect between the different components was also observed. This investigation showed that HAp-based sunscreens of marine origin are a valid alternative to commercial products, safe for the health of the customers and, being non-photocatalytic, do not pose a threat to the environment. [ABSTRACT FROM AUTHOR]

A series of clay/Fe 2 O 3 red hybrid pigments with vivid color, good stability and low cost was synthesized via a facile one-step reaction of Fe(III) solution with sepiolite (Sep) or halloysite (HNTs). Sep or HNTs plays key roles to promote the in-situ transformation of Fe(III) into red hybrid pigments, because only black product was formed from Fe(III) in the absence of them. The addition of Sep and HNTs avoids the usage of any chemical precipitants, which is greatly superior to the traditional process. The a * coordinate values of the sepiolite/Fe 2 O 3 (Sep/Fe 2 O 3 ) and halloysite/Fe 2 O 3 (HNTs/Fe 2 O 3 ) hybrid pigments are 25.1 and 34.4, respectively, which indicate they have well red color performance. The positive influence of Sep or HNTs on the crystallization process and dispersion of Fe 2 O 3 particles is responsible for the good red color. In addition, the hybrid pigments exhibit excellent stability to resist external attacks such as light, acid, alkaline, organic solvents and high temperature, and can be facilely spray-coated onto various substrates, e.g., glass, wood plate, ceramic plate, stone plate, and polyester plate, etc. Therefore, they are potential to be used as promising low-cost environment-friendly colorants in many fields such as ceramic, painting, coating, and printing. [ABSTRACT FROM AUTHOR]

A novel sorbent (SCX) composed of mixed iron oxides and hydroxides was studied to assess its suitability for H 2 S removal from biogas finalized to high temperature fuel cell systems. From an industrial point of view, the potential usage of this product would have a beneficial impact on operational costs, since it is less expensive than activated carbons. Moreover, it is a non-hazardous landfilled product with a reduced environmental impact and it can be easily regenerated. Sorbent SCX was tested in different operative conditions, evaluating the influence on sorption capacity of gas hourly space velocity (GHSV), gas composition (inlet H 2 S concentration, gas matrix, humidity), reactor temperature and filter geometry. As main outcomes, the experimentation highlighted: i) a hyperbolic increase in adsorption capacity as GHSV decreased, ii) a parabolic performance enhancement with increasing temperature and iii) a negative effect of humidity. Moreover, a comparison with commercial activated carbons typically used for the same purpose (Cu–Cr or KOH–KI treated) was performed, identifying the optimal operative parameters to obtain higher H 2 S sorption capacity for SCX sorbent. Specifically, SCX showed its potential in terms of H 2 S removal for GHSV lower than 330 h −1 , values of particular interest for many practical applications. In this case, an improved removal capability is obtained with respect to the ones exhibited by the considered carbons. Moreover, quantitative evaluations provided for unitary installed power (1 kW e fuel cell-based systems) highlighted the possibility to have more compact (volume reduction of about 50%) and cheaper (cost reduction up to six times) filters. [ABSTRACT FROM AUTHOR]

Properties of boehmite and hematite powders formed under hydrothermal conditions are well known. However, a synergistic effect is expected when the γ-AlOOH/α-Fe 2 O 3 composite powders are obtained under the same conditions. Hence, it should be possible to improve the properties (including adsorption) as compared to these of pure γ-AlOOH and α-Fe 2 O 3 . The γ-AlOOH/α-Fe 2 O 3 composite powders were synthesized by hydrothermal method using metal nitrate solutions and urea as precursors. The influence of the [Al 3+ ]:[Fe 3+ ] ratio on the phase composition, textural properties, morphology, and thermal effects of composites was investigated. The γ-AlOOH/α-Fe 2 O 3 composite powders had a smaller particle size and showed higher specific surface area and sorption capacity as compared to these of pure γ-AlOOH and α-Fe 2 O 3 . The sample prepared by using a solution with [Al 3+ ]:[Fe 3+ ] = 1 showed the highest specific surface area (98.1 m 2 /g) and adsorption capacity (4.17 mg/g) in the removal of Cr(VI) from aqueous solutions. Sorption experiments showed that the mean free adsorption energy is below 8 kJ/mol for all samples, indicating the adsorption process as the physical in nature and suggesting the possibility of Cr(VI) desorption and adsorbent regeneration. [ABSTRACT FROM AUTHOR]

Iron oxide nanostructures are of particular interest because they can be used as photocatalysts in water splitting due to their advantageous properties. Electrochemical anodization is one of the best techniques to synthesize nanostructures directly on the metal substrate (direct back contact). In the present study, a novel methodology consisting of the anodization of iron under hydrodynamic conditions is carried out in order to obtain mainly hematite (α-Fe 2 O 3 ) nanostructures to be used as photocatalysts for photoelectrochemical water splitting applications. Different rotation speeds were studied with the aim of evaluating the obtained nanostructures and determining the most attractive operational conditions. The synthesized nanostructures were characterized by means of Raman spectroscopy, Field Emission Scanning Electron Microscopy, photoelectrochemical water splitting, stability against photocorrosion tests, Mott-Schottky analysis, Electrochemical Impedance Spectroscopy (EIS) and band gap measurements. The results showed that the highest photocurrent densities for photoelectrochemical water splitting were achieved for the nanostructure synthesized at 1000 rpm which corresponds to a nanotubular structure reaching ∼0.130 mA cm −2 at 0.54 V (vs. Ag/AgCl). This is in agreement with the EIS measurements and Mott-Schottky analysis which showed the lowest resistances and the corresponding donor density values, respectively, for the nanostructure anodized at 1000 rpm. [ABSTRACT FROM AUTHOR]

Magnetisation of carbonaceous adsorbent using iron oxide (Fe x O y ) has potential to decrease the recovery cost of spent adsorbent because it could be separated magnetically. However, formation of various phases of Fe x O y and iron hydroxide (Fe x (OH) y ) during synthesis particularly the non-magnetic phases are difficult to control and could significantly reduce the magnetic saturation of the adsorbent. Hence, formation of the most magnetic Fe x O y , Fe 3 O 4, on biochar via oxidative hydrolysis of FeCl 2 under alkaline media was performed to synthesise magnetic adsorbent using pine sawdust biochar (magnetic pine sawdust biochar: MPSB). The Fe 3 O 4 nanoparticles on the surface of biochar contributed to high saturation magnetisation of MPSB, 47.8 A m 2 /kg, enabling it to be separated from aqueous solution using a magnet. MPSB were examined physically and chemically using various techniques. Sorbent-stability, parametric, kinetics, isotherm, thermodynamic and sorbent-regeneration studies were performed to comprehend the potential of MPSB as adsorbent to remove an emerging contaminant, sulfamethoxazole (SMX) from aqueous solution. Results showed that MPSB was stable within solution pH 4–9. Adsorption of SMX onto MPSB was favourable at low pH, fast and best described by Redlich-Peterson model. Adsorption was exothermic with physisorption possibly due to hydrophobic interaction and spent adsorbent could be regenerated by organic solvents. [ABSTRACT FROM AUTHOR]

A carbonate-based mesoporous magnetic adsorbent IO@CaCO 3 was synthesized via a hydrothermal method. The IO@CaCO 3 adsorbent removed both anionic (As(V) and Cr(VI)) and cationic (Pb(II)) heavy metal ions at a rate orders of magnitude faster than any conventional adsorbents reported to date; due to synergistic effect of needle-like IO and CaCO 3 , it completely removed (99.99%) the toxic heavy metal ions from wastewater in only 9 min. In addition, it exhibited excellent As(V), Cr(VI), and Pb(II) removal capacities of 184.1, 251.6, and 1041.9 mg g −1 , respectively, over a wide pH range. The heavy metal ion adsorption mechanism involves ion-exchange reactions between the cationic/anionic heavy metal ions and the positively/negatively charged groups on the adsorbent. Along with the batch adsorption tests, heavy metal ion removal by IO@CaCO 3 was also performed by column filtration, demonstrating the potential of IO@CaCO 3 for use in practical applications. Moreover, the excellent removal efficiencies of the adsorbent for the heavy metal ions up to drinking water level and its easy separation by an external magnetic field enabled it to be effectively reused. [ABSTRACT FROM AUTHOR]

Mixed oxides, α - Fe 2 O 3 /Bi 2 WO 6 , were prepared using a mechanical mixing procedure by adding to the Bi 2 WO 6 previously obtained by hydrothermal method the corresponding amount of a prepared α - Fe 2 O 3, the latter obtained by thermal decomposition of Fe(NO 3 )∙9H 2 O. The physicochemical surface, structural, morphological characteristics and optical properties of the samples, single and mixed, were determined by BET, XRD, FE-SEM, XPS and UV–vis diffuse reflectance spectroscopy. UV–vis diffuse reflectance spectra showed that incorporating a 5%wt. of α-Fe 2 O 3 to the corresponding amount of Bi 2 WO 6 sample broadened the visible light absorption of Bi 2 WO 6 as expected. The photocatalytic activity, of single and mixed catalysts, to degrade a selected dye such as Methyl Orange (MO) as well as the transparent substrate Phenol (Ph) was studied, in aqueous medium (pH ≈ 5.5) under UV and sun-like illumination conditions in the absence and presence of H 2 O 2 . In the present study the use of a α-Fe 2 O 3 -Bi 2 WO 6 /H 2 O 2 system demonstrate much higher photocatalytic efficiency to degrade both MO and Ph than pristine Bi 2 WO 6 or α - Fe 2 O 3, single or mixed. Using the system α-Fe 2 O 3 -Bi 2 WO 6 /H 2 O 2 , around 85% of MO was degraded in 60 min under sun-like illumination whereas 100% was degraded in 60 min under UV-illumination. However, just around 30% of Ph was degraded in 120 min in the α-Fe 2 O 3 -Bi 2 WO 6 /H 2 O 2 system under sun-like illumination whereas around a 95% was degraded in 90 min under UV-illumination. Under UV-illumination, the generation of hydroxyl radicals is favorable; whereas under sun-like illumination, only the small fraction of the UV can produces the OH. Under illumination, the H 2 O 2 could react with photoinduced electrons from the photocatalysts leading to the production of hydroxyl radicals ( OH). [ABSTRACT FROM AUTHOR]

Preparation and use of an iron containing catalyst, Fe 2 O 3 modified kaolin (Fe 2 O 3 -KLN), was investigated to develop a heterogeneous electro-Fenton process for the electrochemical oxidation of enoxacin (ENXN). The characterizations of the prepared Fe 2 O 3 -KLN were performed using different methods. Mineralization efficiency of the electro-Fenton method increased in the presence of Fe 2 O 3 -KLN catalyst. The experimental variables that affect the efficiency of heterogeneous electro-Fenton treatment were investigated. Mineralization rates of ENXN reached its maximal value in the presence of 0.3 g Fe 2 O 3 -KLN at 300 mA. While the mineralization efficiency of ENXN was much higher in pH values of 2.0 and 3.0, the total mineralization of ENXN was also observed at pH values of 5.1 and 7.1. A very small decrease (0.5%) was found in the activity of Fe 2 O 3 -KLN after five runs. Characterization studies showed that the change in the morphology and chemical structure of Fe 2 O 3 -KLN during the experiments was negligible. The amount of leached iron (∼0.006 mM) revealed that hydroxyl radicals were mainly produced by heterogeneous reactions of surface iron species. GC–MS, HPLC and LC–MS analysis allowed the identification of some of organic oxidation intermediates. Inorganic oxidation intermediates (F − , NO 3 − and NH 4 + ) were identified by IC analysis. An oxidation pathway was proposed for the mineralization of ENXN. [ABSTRACT FROM AUTHOR]

An Al 2 O 3 support with flower-like morphology was used as the support of iron oxide catalyst for oxidative dehydrogenation of ethylbenzene with CO 2 . A commercial Al 2 O 3 was also used for comparison. These catalyst materials were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N 2 physisorption, H 2 temperature programmed reduction (H 2 -TPR), cyclic voltammetry (CV), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and CO 2 temperature programmed desorption (CO 2 -TPD) techniques. It was found that the concentration of O 2− anions on the flower-like Al 2 O 3 surface was significantly higher than that on the commercial Al 2 O 3 surface, leading to large amounts of highly dispersed Fe x O y clusters on flower-like Al 2 O 3 in contrast with large Fe 2 O 3 particles mainly present on commercial Al 2 O 3 . A possible formation mechanism of the small Fe x O y clusters was proposed. The catalytic results indicated that the highly dispersed Fe x O y clusters possessed an excellent catalytic activity, since the ethylbenzene conversion over Fe 2 O 3 /flower-like Al 2 O 3 was 1.6 times higher than that over Fe 2 O 3 /commercial Al 2 O 3 . This work provides a new route for designing supported iron catalysts that are widely used, and flower-like Al 2 O 3 is expected to be a promising catalyst support for oxidative dehydrogenation of ethylbenzene with CO 2 . [ABSTRACT FROM AUTHOR]

Carbon monoxide production from carbon dioxide via isothermal reverse water–gas shift chemical looping (RWGS-CL) is studied with a modified iron oxide oxygen carrier material (80 wt% Fe 2 O 3 –Ce 0.5 Zr 0.5 O 2 ). The material is characterized by TEM, XRD and thermogravimetry at temperatures from 750 °C to 850 °C and gas mole fractions of H 2 and CO 2 from 0.05 to 0.75, respectively. High temperature and high reactant concentrations favor the oxidation and reduction of the material during repeated redox cycles. The reaction rate of reduction is always faster than that of oxidation applying the same gas concentration of H 2 and CO 2 , respectively. The long term stability of the material is investigated with 500 redox cycles in a plug flow reactor. The material shows gradual deactivation lowering the CO yield during the first 100 redox cycles. After that, a steady state CO yield is reached for the next 400 redox cycles. Deactivation is attributed to surface sintering which results in slower reaction kinetics. TG data was used for a kinetic analysis applying the master plot method. The experimental data for oxidation and reduction indicated reaction mechanisms, which are well described by a reaction order and a geometrical contraction model. After parameter estimation, a good agreement between the model and the TG data was achieved with the reaction order and geometrical contraction model for oxidation and reduction, respectively. The RWGS-CL process can be used for sustainable CO production from CO 2 if the energy for the process and for H 2 production is supplied by renewable sources. [ABSTRACT FROM AUTHOR]

Benefiting from the hydrophilicity and modifiability, aminated iron oxide nanoparticles play significant roles in the construction of magnetically responsive functional materials, and are then widely used in the field of biomedicine and water purification. Using the deep eutectic solvent (DES) composed of urea and choline chloride as an electrolyte, amino-grafted water-soluble maghemite (γ -Fe 2 O 3) nanocrystals have been synthesized by organic electrolysis (DES-electrolysis). In the present work, the DES containing ferrous ions is used as the electrolyte to verify whether magnetite (Fe 3 O 4) can be prepared by that organic electrolysis strategy. The results show that, regardless of the presence or absence of ferrous ions in the DES-based electrolyte, the resulting nanocrystals are maghemite rather than magnetite. The synthesized amino-grafted γ -Fe 2 O 3 nanoparticles can also be highly and stably dispersed in water. The present work deepens the understanding of the formation mechanism of amino-grafted water-soluble maghemite nanocrystals synthesized by DES-electrolysis. [Display omitted] [ABSTRACT FROM AUTHOR]

Abundant endeavors have been undertaken to explore high-quality and inexpensive materials for capacitive deionization desalination. However, one major problem is the sluggish adsorption rate and inferior adsorption performance of these materials in practical applications. Herein, nitrogen-doped carbon nanofiber-reinforced hierarchical hollow iron oxide nanorods grown on electrospinning carbon nanofibers (denoted Fe 2 O 3 @CNFs) were rationally designed and synthesized for high-efficiency capacitive deionization. Such composition and distinctive hierarchical porous structure prevent agglomeration of Fe 2 O 3 nanorods, boosting the ionic/electronic transport through the synergistic effect between the Fe 2 O 3 nanorods and N-doped carbon nanofibers. When employed as a cathode for capacitive deionization without adding any polymeric binder or conductive additives, this material exhibits a high adsorption capacity of 114.97 mg/g and a rapid salt adsorption rate (7.79 mg/g min). Moreover, the sodium storage mechanism was revealed through ex situ XRD, EDX mapping and ex situ XPS. Density functional theory (DFT) calculations reveal that the electrons are redistributed at the heterojunction interface, refining the electrochemical activity. This work is anticipated to afford an innovative path for the development of porous transition metal oxide-based fibers with outstanding effectiveness and stability toward environmental research of high-performance capacitive deionization. [Display omitted] • A free-standing hierarchical hollow Fe 2 O 3 @CNFs hybrid electrode was fabricated. • A high electrosorption capacity and a rapid salt adsorption rate were achieved. • The hollow structure alleviates volume expansion and facilitates ion diffusion. • The faradic reaction and electroadsorption coupling removal mechanism was proven. • DFT were implemented to provide in-depth insights into the storage mechanism. [ABSTRACT FROM AUTHOR]

• An innovative galvanic cell simulated electrochemical reactions in pipe scale. • Electrochemical evidence verified the reduction of iron oxides in anoxic conditions. • Kinetics plays most important role in the reduction of iron oxide scale. • Goethite was transformed into magnetite as a result of the reduction of pipe scale. Iron release from pipe scale is an important reason for water quality deterioration in drinking water distribution systems (DWDS) globally. Disruption of pipe scale, release and transformation of iron compounds are hot topics in the field of water supply. The aim of this study is to determine whether and how ferric components in pipe scale be reduced under anoxic condition. In this study, new investigation approaches were applied, which include simplifying the complex scale into electrode pairs, developing novel simulating reactors and conducting tailored electrochemical assays. A galvanic cell reactor with anode of metallic iron (Fe0) and various cathode made of certain iron oxide (FeO x) was firstly developed to simulate the complex niche and components of pipe scale. Electrochemical methods were used to study the reduction characteristics of scale. The results proved that reduction of iron oxide scale did occur under anoxic condition. Electromotive forces between various electrodes match the Nernst Equation quite well. As main components in pipe scale, lepidocrocite (γ-FeOOH) was found to be the most reducible iron oxide but at low rate, while goethite (α-FeOOH) has weak reducibility but can be quickly reduced. As a result of electrochemical reactions, goethite in pipe scale was transformed into magnetite (Fe 3 O 4). By these means, electrochemical reaction mechanisms of pipe scale disruption were revealed, which is helpful to restrain pipe corrosion and water deterioration in DWDS. [Display omitted] [ABSTRACT FROM AUTHOR]

Molybdenum (Mo) is a naturally-occurring trace element in drinking water. Most commonly, molybdate anions (MoO 4 2-) are in well water and breast milk. In addition, it is used in medical image testing. Recently, the EPA classified Mo as a potential contaminant, as exposure can lead to health effects such as gout, hyperuricemia, and even lung cancer. We have assessed the sorptive removal of aqueous molybdate using Douglas fir biochar (DFBC) and a hybrid DFBC/Fe 3 O 4 composite containing chemically-coprecipitated iron oxide (Fe 3 O 4). Adsorption was studied at various: pH values, equilibrium times (5 min-24 h), initial Mo concentrations (2.5–1000 mg/L), and temperatures (5, 25, and 40 °C) using batch sorption and fixed-bed column equilibrium methods. Langmuir capacities for DFBC and DFBC/Fe 3 O 4 (at pH 3, 2 hrs equilibrium) were within 459.3–487.9 mg/g and 288–572 mg/g, respectively. These adsorbents and their Mo-laden counterparts were characterized by elemental analysis, BET, PZC, SEM, TEM, EDS, XRD, and XPS. MoO 4 2- adsorption on DFBC is thought to be governed primarily via electrostatic attraction. Adsorption by DFBC/Fe 3 O 4 is primarily governed by chemisorption onto magnetite surface hydroxyl groups, while electrostatics prevail in the DFBC-exposed phase. Stoichiometric precipitation of iron molybdates triggered by iron dissolution was also considered. The data suggest that DFBC and DFBC/Fe 3 O 4 are promising candidates for molybdate sorption. [Display omitted] • Douglas fir biochar and its iron oxide analogue removed ∼500 mg/g aqueous molybdate. • Adsorption from anion mixtures and complex natural water was robust. • Fixed-bed column capacity for iron oxide/biochar was ∼19 mg/g. • Uptake was governed by chemisorption, hydrogen bonding and preciptiation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A template method is utilized to study the hollow structure that controls the Fe 3 O 4 @C void size. • The relationship between the performance of LIBs and hollowness of iron oxide was systematically studied. • Th excellent performance of LIB was obtained, the specific capacity 915 mAhg−1 at a current density of 0.1C after 100 cycles. Lithium-ion battery anode materials such as iron oxide suffer from large volume expansion during lithiation. In light of this problem, this work uses a template method to investigate the hollow structure that controls the Fe 3 O 4 @C void size. In the experiment, the hollow structure is controlled by the dosage of ethyl orthosilicate (TEOS), and Fe 2 O 3 is coated with phenolic resin to reduce carbon to obtain an anode electrode material with excellent performance. The microstructure and morphology of the samples are analyzed by X-ray diffraction (XRD), Brutern-Emmett-Teller (BET), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and their electrical properties are characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic intermittent titration analysis, and galvanostatic charge–discharge. According to the results, Fe 3 O 4 @C-1.0 has a large vacancy, and the structure does not crack during the battery charging and discharging process. Furthermore, it exhibits excellent electrochemical properties, rate performance, and stable cycle performance. [ABSTRACT FROM AUTHOR]

ortho -Nitroaniline (o -NA) compounds are deemed to be a strongly toxic pollutant in nature and potentially carcinogenic; however, they are frequently utilized to synthesize dyes, pesticides, medicines, fungicides, pigments, and other organic chemicals. Their detection in an aqueous medium is fundamentally required to avoid the potential hazardous being created by these compounds. In this study, a novel sensor based on an Iron oxide (Fe 3 O 4) containing highly dispersed nitrogen-doped carbon quantum dots (N -CQDs@Fe 3 O 4 NFs) was demonstrated for the electrochemical detection of o -NA using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques. N -CQDs@Fe 3 O 4 NFs were synthesized by hydrothermal method and studied by various analytical and spectroscopy techniques, which collectively reveal that the as-prepared composite has superior physical and chemical properties. The DPV study indicated that the o -NA sensor had a good limit of detection, linear range, and sensitivity in the range of 1.2 nm, 0.03–386.84 μ M, and 36.5575 μ A μM−1 cm−2, respectively, along with the sensor showed superior sensitivity when compared to the previously reported modified electrodes. Further, N -CQD/Fe 3 O 4 NFs worked as heterogeneous catalysts for the photocatalytic reduction of o -NA to o -phenylenediamine (o -PD) in an aqueous medium. The reaction was examined under UV–Visible spectroscopy, and the complete photocatalytic reduction was observed for the N -CQD/Fe 3 O 4 NFs in about 6 min with 96% as compared to other control samples; thus, authenticating the superiority of the synthesized composite in rendering the real-time applications. [Display omitted] • N -CQDs@Fe 3 O 4 NFs catalyst was prepared by hydrothermal method to detect the environmentally hazardous organic pollutant. • The o -NA sensor showed an excellent limit of detection of about 1.2 nM. • In addition, the N -CQDs@Fe 3 O 4 NFs catalyst is used for the photo-catalytic reduction of o -NA to OPD. • The electrocatalytic and photocatalytic studies are performed by CV, DPV, and UV–Visible spectroscopy. [ABSTRACT FROM AUTHOR]

In this work, graphene oxide nanosheets (GO) are dual functionalized with Fe 3 O 4 nanoparticles and hydroxypropyl cellulose (CLS) for chemo/phototherapy. The TEM, XRD, FTIR, Raman, UV, TG, DLS, and VSM analyses were used to confirm the CLS and Fe 3 O 4 incorporated GO (CLS@mGO) nanobiocomposite structure. Functionalization of magnetite graphene oxide surface by CLS not only improved biocompatibility, colloidal stability, and entrapment efficiency for paclitaxel (PTX) but also accelerated PTX release. Under 808 nm laser light, the CLS@mGO-PTX nanobiocomposite displayed good photothermal features. The CLS@mGO-PTX nanobiocomposite exhibited high photothermal conversion efficiency (47.85%) and photo stability. The notable synergistic chemo/photothermal impacts have also been determined by the in vitro experiments in killing MCF-7 cancer cells. The results of these experiments exhibited that compared to single phototherapy and chemotherapy, chemo/phototherapy could more effectively kill cancer cells by synergetic anticancer impact. Therefore, the CLS@mGO-PTX nanobiocomposite has great potential for chemo/phototherapy. [Display omitted] • CLS-functionalized magnetite mGO nanobiocomposite was developed for chemo/PTT. • CLS@mGO showed enhanced biocompatibility, thermal, colloidal and photo stability. • It displayed superparamagnetic behavior and high entrapment efficiency for PTX. • A synergetic therapeutic effect was noticed when utilizing 808 nm laser and PTX. • CLS@mGO-PTX nanobiocomposite showed pH-sensitive PTX release. [ABSTRACT FROM AUTHOR]

The performance and the change characteristic of iron oxide/arenaceous sorbent in the regeneration reaction are systematically investigated by studying the effects of temperature, space velocity and O 2 concentration on the sorbent in a fixed-bed quartz reactor. Sulfidation-regeneration cycles were also conducted to evaluate the reusability of the sorbents. The surface and bulk structural features of the sorbents, both before and after regeneration, were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, energy dispersive spectroscopy, Fourier transform infrared spectroscopy and N 2 adsorption-desorption. The results show that the sorbents exhibit the highest regeneration rate at the conditions of 6 vol.% O 2, 650 °C, and space velocity of 3000 h −1 . After five sulfidation-regeneration cycles, the breakthrough curves of regenerated sorbents changed slightly and the regeneration rates of the regenerated sorbents still exceeded 95%. The characterization data indicates that the outer layer electron density of surface atoms decreased in the regeneration process, which adversely affects the adsorption rate of acidic H 2 S and the reaction rate of H 2 S with Fe 2 O 3 on the surface of sorbents. It can be seen from XRD analysis that the particle size of the sorbent gradually increased as the number of sulfidation-regeneration cycles increased, leading to reduced surface area and blocked pore structure. Furthermore, the internal structure deteriorated due to sintering, which resulted in the lowered sulfidation performance of the regenerated sorbent. [ABSTRACT FROM AUTHOR]

Composite organic/inorganic latexes encapsulating iron oxide (IO) nanoparticles of maghemite (γ-Fe 2 O 3 ) were successfully synthesized by surfactant-free reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion polymerization. γ-Fe 2 O 3 was first dispersed in an aqueous solution containing a statistical copolymer constituted of acrylic acid (AA) and n -butyl acrylate (BA) units, prepared by RAFT polymerization (so-called macroRAFT agent). Taking benefit from the affinity of carboxylic acid groups for iron oxide, the P(AA 10 - co -BA 10 ) macroRAFT agent was adsorbed onto the surface of IO nanoparticles leading to the formation of macroRAFT/IO clusters. The interaction between the macroRAFT agent and the IO surface was investigated by the study of the adsorption isotherms, indicating that the amount of adsorbed macroRAFT agent increased with increasing macroRAFT concentration. However, a high fraction of the macroRAFT chains (up to 47%) remained in the aqueous phase. The clusters were then engaged in batch emulsion polymerization of styrene or of methyl methacrylate (MMA)/BA mixtures. IO encapsulation was however unsuccessful, and a phase separation between the polymer and the IO clusters was observed. In contrast, semi-batch emulsion polymerization of MMA/BA (90/10 wt ratio) led to effective encapsulation. Morphology studies suggest that the formation of stable latexes containing large IO clusters mainly depends on the concentration of the macroRAFT agent and the pH. Under optimized conditions, a latex with superparamagnetic properties ( M s = 16.2 emu g −1 ) encapsulating almost all the initial IO nanoparticles was successfully produced. [ABSTRACT FROM AUTHOR]

The novel iron-oxide based glass-fiber catalysts (GFC) for the H 2 S selective oxidation uses the support in form of the glass microfibrous fabric, premodified by external layer of secondary porous SiO 2 support. The specific activity of FeOx-SiO 2 /GFC catalyst per unit mass of active component exceeds that of the similar conventional Fe 2 O 3 /Al 2 O 3 catalyst by more than an order of magnitude due to the more dispersed state of active component in the GFC (1–2 nm compared to 15–30 nm in conventional catalyst). The proposed GFC also looks advantageous in terms of mass transfer efficiency and easy scale-up. [ABSTRACT FROM AUTHOR]

Phase-field method is used to simulate the growth of iron whiskers on a gas–solid interface by changing the oxygen content in iron oxide. Results show that oxygen content significantly influences not only the crystal lattice but also the diffusion direction of iron ion vacancies and iron ions, wherein iron ions diffuse to low-oxygen-content areas and iron ion vacancies diffuse to high-oxygen-content areas. The catastrophic swelling of the micro-area volume and the growth of iron whiskers are caused by the enrichment of iron ions in low-oxygen-content areas. The simulation revealed the effects of the reduction rate and the oxygen potential of gas. Iron whiskers are longer and stronger when the oxygen potential of reducing gas decreases from −133.96 kJ·mol −1 to −160.01 kJ·mol −1 or when the reduction rate increases from 6.3 × 10 −3 mol·s −1 to 7.3 × 10 −3 mol·s −1 . Iron whiskers can appear earlier with a low oxygen potential or a high reduction rate. Both oxygen potential and reduction rate promote the nucleation and growth of iron whiskers. [ABSTRACT FROM AUTHOR]

In this paper, OpenFOAM was employed to numerically investigate syngas (H 2 and CO) production by the simultaneous splitting of H 2 O and CO 2 via thermochemical redox cycle based on iron oxide (Fe 3 O 4 ). The effects of operating conditions such as pressure, temperature and species reactant ratios on syngas yield were investigated. The results indicated that amount of syngas yield was highly dependent on the reduction temperature. It was found that the process at high pressure could lower the reaction temperature and increased species production rate. The overall syngas yield increased from 1.34% up to 98.65% when the pressure increased from 5 to 20 atm. The analysis of the results showed that the syngas yield and the syngas composition were strongly influenced by the ratio of H 2 O/CO 2 ( γ g ). The highest syngas purity (ratio of H 2 /CO ( γ s )) = 3.36 was reached at γ g = 2. The optimum operating conditions for hydrogen-rich syngas production were obtained when γ g = 2 under 1600 K at 20 atm. [ABSTRACT FROM AUTHOR]

Au/α-Fe 2 O 3 catalysts have been prepared by deposition-precipitation. The support α-Fe 2 O 3 has been previously synthesized by precipitation technique. The effect of thermal treatment on structural, morphological and redox properties of Au/α-Fe 2 O 3 samples have been thoroughly studied for the samples calcined at 150, 200 and 300 °C, together with a non-calcined sample. Their catalytic activity toward CO oxidation in the presence of hydrogen (CO-PROX) has been tested. The results showed that the gold particle size and surface adsorbed oxygen changed with the calcination temperature, being the minimum for the sample calcined at 200 °C. There was not detected cationic gold by X-ray photoelectron spectroscopy (XPS) in none of the samples. The presence of gold promoted notably the reduction of the iron oxide. The highest activity for CO-PROX was achieved by the non-calcined catalysts (simply dried at 110 °C), while the sample calcined at 200 °C was the least active. The catalysts activity was assigned to the gold particle size and surface adsorbed oxygen. [ABSTRACT FROM AUTHOR]

Alternating reductions with hydrogen and oxidations with steam have been carried out on solids with improved redox capacity showing the benefits of different synthesis methods in the steam-iron process (SIP). Solids chosen were a commercial hematite, a lab-made iron oxide doped with ceria and alumina and hematite synthesized by freeze-casting technique. The first one shows a high loss of reactivity from the first cycle on while the others keep their reduction capacity along three consecutive cycles and beyond. Isothermal experiments were also performed with the best two solids. Although all of them had hematite as the starting material, they have shown significant differences in behaviour respecting the original commercial hematite depending on the chemical (inclusion of additives that account for only 2 wt% of the solid mass) or physical (macroporosity) properties. Also the effect of long lasting runs with up to 10 cycles (reduction + oxidation) have been performed at different reduction temperatures showing a slightly higher stability of the pure iron oxide pellets produced by freeze-casting versus an iron oxide with alumina and ceria selected as structural stabilizers and accelerators of the reduction/oxidation reaction. [ABSTRACT FROM AUTHOR]

Fe 3 O 4 nanoparticles synthesized by a base catalyzed method are tested as anode material for Li-ion batteries. The pristine nanoparticles are morphologically characterized showing an average size of 11 nm. Electrodes are prepared using high-molecular weight Poly (acrylic acid) as improved binder and ethanol as low cost and environmentally friendly solvent. The evaluation of electrochemical properties shows high specific capacity values of 857 mA hg −1 after 200 cycles at a specific current of 462 mAg −1 , as well as an excellent rate capability with specific current values up to 18480 mAg −1 . To the best of our knowledge, this is the first report of Fe 3 O 4 nanoparticles cycling with PAA as binder. [ABSTRACT FROM AUTHOR]

This work investigates the redox cycling effect on the physicochemical characteristics and gas permeation behaviour of binary metal oxide (iron/cobalt) silica membranes prepared by sol–gel method from tetraethyl orthosilicate, cobalt and iron nitrates, peroxide and water. A Fe/Co ratio of 10/90 conferred more stable silica microstructure under redox cycling, contrary to Fe/Co ratios ⩾25/75 which led to structural densification after the first redox cycle. The gas permeance redox effect of Fe/Co = 10/90 silica membranes resulted in a switchable permeance increase and decrease as the membrane was reduced and oxidised, respectively. However, the extent of the switchable changes were not constant and tended to decrease at each cycle, as evidenced by the He/CO 2 permselectivity shift from a higher value of 130 (first oxidation cycle) down to 80 (third oxidation cycle). It was found that a shift in temperature corresponding to the exothermic oxidation peak, attributed to the progressive changes in the formation of Fe x Co 1−x O y mixed oxide embedded in the silica matrix at each redox cycle. This was further supported by the sequential disappearance of the infrared absorbance peak at 565 cm −1 upon redox cycling, thus demonstrating structural re-arrangement of the membrane. The permselectivity of He and H 2 over CO 2 sequentially decreased at a higher ratio for after the oxidation cycle, as a result of the silica matrix densification at high temperatures (400 °C). [ABSTRACT FROM AUTHOR]

A bio-friendly nanostructured cellulose nanocrystal (CNC) sheet with iron oxide grown on it acting as a nitrogen dioxide (NO 2 ) gas sensor was fabricated by hydrothermal method. The structural investigation was done to monitor the growing mechanism of iron oxide on CNC surface using electron microscope as well as physical and chemical characterization methods. The sensing performance test for NO 2 molecules demonstrates that the devices are highly sensitive and fully recoverable at room temperature, which is attributed to the excellent access of nitrogen dioxide molecules to the sensor surface via CNC. The effects of the temperature, durability, and flexibility of sensor are investigated. The reported sensor performance is a huge improvement towards low power consumption and its room temperature operation augurs well for use in various applications. [ABSTRACT FROM AUTHOR]

Using high-resolution scanning tunneling microscopy (STM) we have studied the oxidation of ultrathin FeO films grown on Pt(111). At the initial stage of the FeO film oxidation by atomic oxygen exposure, we identified three distinct types of line defects, all of which form boundaries between FeO domains of opposite orientation. Two types of line defects appearing bright ( type-i ) and dark ( type-ii ) in the STM images at typical scanning parameters are “metallic”, whereas the third line defect exhibits nonmetallic behavior ( type-iii ). Atomic-scale structure models of these line defects are proposed, with type-i defects exhibiting 4-fold coordinated Fe atoms, type-ii exhibiting 2-fold coordinated O atoms, and type-iii exhibiting tetrahedrally-coordinated Fe atoms. In addition, FeO 2 trilayer islands are formed upon oxidation, which appear at FCC-type domains of the moiré structure. At high scanning bias, distinct protrusions on the trilayer islands are observed over surface O ions, which are assigned to H adatoms. The experimental data are supported by density functional theory (DFT) calculations, in which bare and hydroxylated FeO 2 trilayer islands are compared. Finally, we compare the formation of O-rich features on continuous FeO films using atomic oxygen with the oxidation of Pt(111)-supported FeO islands accomplished by O 2 exposure. [ABSTRACT FROM AUTHOR]

Iron oxide, as a promising anode material, has environmental friendliness, high theoretical capacitance, and a wide voltage window. Cobalt-doped iron oxide was loaded on flexible carbon cloth (Co-Fe 2 O 3 @CC) via hydrothermal reaction. Cobalt doping changes the iron oxide's crystal structure and improves the conductivity of the iron oxide. At the same time, it also increases the oxidation state of iron oxide and improves the pseudocapacitance of the electrode material. The reaction conditions were controlled to prepare iron oxide nano-spheres having porous morphology. The porous structure increases the area where the electrode material is reacted. The area-specific capacitance of the Co-Fe 2 O 3 @CC electrode material is 315.6 mF cm−2, which is 137.2% higher than that of pure Fe 2 O 3 @CC(133 mF cm−2). The capacitance is unchanged before and after 200 times of 90° bending. The voltage window of assembled Co-Fe 2 O 3 @CC//Ni-MnO 2 @CC asymmetric supercapacitors is 0–2 V. The energy density is 0.96 mWh cm−3 and the power density is 28.6 mW cm−3, which has excellent electrochemical performance. After 4000 cycles at a current density of 10 mA cm−2, the capacitance is maintained at 85%. Flexible asymmetric supercapacitors have potential applications in the field of flexible wearables. [Display omitted] • Cobalt was doped into Fe 2 O 3 @CC electrode material (Co-Fe 2 O 3 @CC) via hydrothermal reaction. • Co-Fe 2 O 3 formed nanospheres with nanopores inside. • Co-Fe 2 O 3 @CC electrode material had large area capacitance and good flexibility. • Flexible asymmetric supercapacitors had large area specific capacitance and excellent energy density. [ABSTRACT FROM AUTHOR]

• Size effect of iron oxide NPs (NP10, NP20, NP30, and NP40) was investigated in pumpkin. • TEM and VSM analyses revealed root-to-shoot translocation of all tested NPs. • NP30 exhibits the highest translocation performance, while a negligible amount of NP10 and NP40 reached to the leaves. • The status of nutrient elements significantly altered depend on NP-type. • The findings could be important for selecting the most suitable NP size for agricultural practices. The ability of nanoparticles (NPs) to migrate in the plant body is an important issue to ensure that the NPs reach the desired tissue and to be able to select the most efficient NPs for agricultural applications. In this study, the size impact of four different iron oxide NPs (8–10, 18–20, 20–40, and 30–50 nm referred as NP10, NP20, NP30, and NP40, respectively) on their translocation in pumpkin was elucidated. To assess the root-to-shoot translocation, phloem sap was examined under transmission electron microscope (TEM). In addition, vibrating sample magnetometer (VSM) and inductively coupled plasma optical emission spectrophotometry (ICP-OES) analyses of stem and leaf tissues were performed to confirm size-dependent translocation. TEM and VSM analyses verified root-to-stem translocation of all tested NPs. The NPs treatment significantly altered the abundances of Mn, Cu, K, P, Al, Mg, and Na in tissues. The iron (Fe) content was abundant in plants treated with NP30 and NP20, and the lowest in plants treated with NP10 and NP40. Together with, only NP30 was found to be significantly translocated to the leaves, where it was 393 mg/kg in DW, about 2.3 times that of control. These findings pointed out the size-dependent translocation of NPs. It seems that biological barriers in the vascular bundle appear to restrict the migration, especially for NPs with an average size of 40 nm and above in pumpkins. These findings are important for selecting the most suitable size of iron oxide NPs for use in agricultural practices. [ABSTRACT FROM AUTHOR]

The discovery of spherical accumulations of iron oxide mineralization on Mars has prompted renewed interest in widespread but enigmatic accumulations of iron oxide on Earth. The rinded iron oxide concretions found in the Navajo Sandstone (Utah, USA) have been among the most extensively studied of these occurrences. At least four different models have been proposed for the formation of iron oxide concretions in the Navajo Sandstone. These include 1) mixing of reduced Fe(II)-bearing and oxygenated groundwaters, 2) neutralization of oxidized, acidic waters by calcite concretions, 3) neutralization of reduced, acidic waters by calcite concretions, and 4) oxidation of siderite by microbes during invasion of the Navajo aquifer by oxygenated groundwaters. We measured δ56Fe values of iron-bearing minerals from whole-rock Navajo Sandstone, concretionary iron oxide cements, iron oxide stains that are oriented in the direction of paleo-groundwater flow, iron oxide stains on the interior of rinded concretions, and ferroan carbonate cements. We have then combined these data with published measurements to evaluate each of the four published models. Whole rock Navajo Sandstone from the Kolob Plateau has been interpreted to be unaltered by bleaching fluids and has a δ56Fe value of 0.21‰. Iron in the Kolob Plateau sample comprises a mixture of hematite grain coatings (δ56Fe = 0.12‰) and a magnetic mineral fraction (interpreted to comprise largely detrital magnetite) that has a higher δ56Fe value (0.45‰). Iron oxide cements have δ56Fe values that are typically negative and as low as −0.74‰. In contrast, iron oxide-stained Navajo Sandstone in close proximity to a rinded iron oxide concretion has δ56Fe values that are 0.9 to 1‰ greater than the δ56Fe value of the associated iron oxide concretion. Finally, ferroan carbonates from the Navajo Sandstone yield δ56Fe values as low as −0.86‰. These values are in good agreement with measurements published previously for lithologies for which comparable measurements have been made. The presence of ferroan carbonates with negative δ56Fe values is evidence that aqueous Fe(II) was transported through the Navajo Sandstone aquifer and produced carbonate mineralization with negative δ56Fe values. The difference in δ56Fe values between the iron oxide concretions and associated iron oxide staining is more consistent with equilibrium fractionation between aqueous Fe(II) and Fe(II) adsorbed on quartz grains than it is with equilibrium fractionation between aqueous Fe(II) and any reduced or oxidized iron oxide mineral species. The negative δ56Fe values of the iron oxide concretions are best explained by oxidation of a reduced iron phase in a closed system from which no aqueous Fe(II) could escape. We interpret the iron isotope data as evidence that iron was stripped from Navajo sand grains by reducing fluids, reprecipitated in the Navajo aquifer as siderite, and oxidized by groundwaters under closed conditions during incision of the Colorado Plateau. • Iron oxide concretions with negative δ56Fe values occur in Navajo Sandstone • Ferroan carbonate in the Navajo Sandstone also has low δ56Fe values • The Navajo Sandstone aquifer contained reduced iron and carbonate-bearing waters • Low δ56Fe values of Navajo concretions unlikely if primary precipitate was iron oxide • Low δ56Fe values are evidence that iron oxide concretions formed from siderite [ABSTRACT FROM AUTHOR]

Introducing an external energy field into water electrolysis is considered as an innovative strategy to improve electrocatalysis for water splitting. However, rationally modulating these external energy fields to synergize electrocatalytic processes remains a great challenge. Herein, phosphate-incorporated iron oxide nanosheet arrays (P-FeO x /IF) are constructed as multifunctional photothermal-electrocatalytic electrodes for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The as-prepared P-FeO x /IF exhibits excellent photothermal conversion performance and enables in-situ surface self-heating under near-infrared (NIR) light irradiation, resulting in a gradual increase in local temperature on the electrode surface. Impressively, the photothermal P-FeO x /IF electrode exposed to NIR light irradiation shows significantly improved electrocatalytic performances with relatively low overpotentials for OER (η 10 : 280 mV) and HER (η 10 : 104 mV) to deliver a current density of 10 mA cm−2. Furthermore, a two-electrode system using photothermal P-FeO x /IF as anode achieves a low cell voltage of 1.685 V. This study provides a new avenue for developing high-performance electrocatalysts incorporating photothermal effects. [Display omitted] • Phosphate-incorporated iron oxide nanosheets are successfully fabricated. • P-FeO x /IF achieves light-to-heat conversion under NIR light irradiation. • P-FeO x /IF presents excellent light-assisted performances for electrocatalytic water splitting. • P-FeO x /IF exhibits long-term durability for photothermal-electrocatalytic water splitting. [ABSTRACT FROM AUTHOR]

Iron oxide is intensively explored for its high capacity and abundant reserves. Suffering from poor conductivity and huge volume variation during repeating lithiation/delithiation, the capacity decays quickly. Herein, carbon coated porous iron oxide nanotubes (FeO x @C) is synthesized via hydrothermal method and subsequent annealing to achieve cycling stability. FeO x @C-2 exhibits excellent rate capability and superior cycling life. As anode material for lithium ion batteries, it delivers a high reversible capacity of 948.5 mAh g−1 at 2 A g−1 after 500 cycles. The initial coulombic efficiency is 88.7% and nearly 100% in the following cycles. The superior electrochemical performance belongs to improved electrical conductivity of carbon coating layer and exceptional stress relaxation of porous hollow structure of nanotube. • Amorphous carbon coated Fe 3 O 4 porous nanotubes (FeO x @C) was synthesized. • The hollow structure of FeO x @C facilitates the Li+ diffusion and the structure integrity. • The carbon layer boosts the conductivity and accommodates the volume variation. • FeO x @C-2 exhibits superior lithium storage performance. [ABSTRACT FROM AUTHOR]

The influence of iron oxide, FeO x , on Pt for CO oxidation was investigated. A film of FeO x , nominally 0.8-nm thick, was added to a Pt/Al 2 O 3 catalyst by Atomic Layer Deposition. The film was found to wet the Pt surface after oxidation at 773 K and 973 K, as shown by aberration-corrected, transmission electron microscopy. In-situ infrared spectra and CO chemisorption measurements showed that the addition of the FeO x greatly suppressed CO adsorption but enhanced CO oxidation rates due to FeO x -Pt interfaces. The FeO x layer also improved the stability of the catalyst by mitigating the sintering of Pt particles at 973 K. • Atomic-scale FeO x overlayer augments the CO oxidation activity and thermal stability of the Pt/Al 2 O 3 at 973 K. • TEM and CO chemisorption shows that FeO x overlayer wets the Pt surface and greatly suppresses CO adsorption on Pt. • In-situ infrared spectra shows that CO oxidation occurs without CO adsorption on FeO x -overcoated Pt catalyst. • FeO x overlayers near Pt enhances CO oxidation rates through the FeO x -Pt interfaces. [ABSTRACT FROM AUTHOR]

• The kinetic data of degradation of PVC, Fe 3 O 4 -PVC and Fe 2 O 3 -PVC were extracted. • Fe 3 O 4 and Fe 2 O 3 were found to hamper PVC de-hydrochlorination. • Crystals of FeCl 2 and FeCl 2 ·2H 2 O were identified using XRD and SEM. • The thermodynamics of chlorination and reduction of Fe 3 O 4 and Fe 2 O 3 were reported. Electric arc furnace dust (EAFD) which is accumulated in large amounts world-wide contains hematite (Fe 2 O 3) and significant quantities of magnetite (Fe 3 O 4). Waste polyvinyl chloride (PVC) also poses a great environmental threat aside to accumulated EAFD. Both of these wastes have shown a great potential for their co-thermal treatment for metal extraction, thus minimising their environmental footprint. Herein, an investigation on the thermal degradation behaviour, reaction products, thermodynamics and the decomposition kinetics of PVC and its stoichiometric mixtures with Fe 3 O 4 and Fe 2 O 3 was conducted using non-isothermal thermogravimetric scans. The kinetic data suggests a significant increase in the average activation energy of PVC de-hydrochlorination from 122.6 ± 24.2 kJ/mol (pure PVC) to 177.0 ± 28.0 and 199.0 ± 77.0 kJ/mol when stoichiometric quantities of Fe 3 O 4 and Fe 2 O 3 were mixed with PVC. The inhibiting effect of both Fe 3 O 4 and Fe 2 O 3 on the degradation of PVC might be assigned to the capturing of emitted gaseous HCl which is known for its catalytic effect. This result suggests that EAFDs containing both Fe 3 O 4 (in large amounts) and Fe 2 O 3 can have an inhibiting effect on the de-hydrochlorination of PVC resulting in longer processing times or the requirement of higher processing temperatures for achieving reasonable reaction rates. [ABSTRACT FROM AUTHOR]

Iron oxide-lignin composites (GLS) were prepared based on the significant role of Fe-OM in the environmental behaviour of heavy metals and lignin binding with iron oxide preferentially in soil. GLS was applied in Cd/Pb immobilization and the stability under acid rain was investigated. The results show that the iron oxide appeared weakly crystalline or amorphous similar to 2-line ferrihydrite after the addition of lignin. Agglomerates of nanoparticles with higher adsorption capacity were observed for GLS. The mobility factor (MF) of Cd/Pb in the soil decreased rapidly after adding GLS. At the 3% dosage, the MF of Cd and Pb in the soil was decreased by 58.94% and 78.15% respectively, which was approximately 5 times that of goethite (GE). The mobile and exchangeable Cd/Pb were converted to organic, amorphous Fe oxide-bound and residue fractions. Under acid rain conditions, MF continues to decline for the GLS group, increasing the organic and amorphous Fe oxide-bound fractions, while for control group (CK) and GE, the trend was the opposite. Lignin could inhibit iron oxide dissolution and stabilize the combination of Cd/Pb and iron oxides in soil. The better stability performance of GLS for Cd/Pb may be related to the higher adsorption capacity and microstructural difference after iron oxide combined with lignin. [Display omitted] • Iron oxide-lignin composites (GLS) show a higher adsorption capacity than goethite. • The mobility of Cd/Pb was decreased significantly after GLS application. • The stability of iron oxide was enhanced after combining with lignin. • GLS application consistently reduces the Cd/Pb leaching under acid rain conditions. [ABSTRACT FROM AUTHOR]