Showing papers on "Iron oxide published in 2020"

Green Synthesis of Magnetic Nanocomposite with Iron Oxide Deposited on Cellulose Nanocrystals with Copper (Fe3O4@CNC/Cu): Investigation of Catalytic Activity for the Development of a Venlafaxine Electrochemical Sensor

Abstract: A screen-printed electrochemical sensor based on Fe3O4@cellulose nanocrystals/Cu nanocomposite (Fe3O4@CNC/Cu) has been constructed for the sensitive detection of venlafaxine. The magnetic Fe3O4@cel...

Activity and degradation study of an Fe-N-C catalyst for ORR in Direct Methanol Fuel Cell (DMFC)

Abstract: In this work a comprehensive study of the activity and stability of a non-precious metal catalyst of type Fe- N- C in acidic media is reported. The catalyst was prepared from polyaniline, dicyandiamide and iron acetate as precursors. Temperature-dependent rotating-disk electrode experiments were performed to determine the activation energy of the catalyst. Besides, load cycle durability tests with and without the addition of methanol show that there is no additional deactivation caused by methanol addition. In a Direct Methanol Fuel Cell (DMFCs) our catalyst performed similarly good in comparison to other Fe-N-C catalysts. Raman and Mossbauer spectroscopy provide valuable information on the structural composition and chemical changes induced by durability and stability testing of the catalyst. While the maximum power density during DMFC operation decreases by 85%, the qualitative distribution of iron sites might indicate the formation of iron and iron oxide clusters as decomposition product associated with the disintegration of FeN4 sites.

Photothermal Conversion of CO2 with Tunable Selectivity Using Fe-Based Catalysts: From Oxide to Carbide

Abstract: Conversion of CO2 into fuels via solar energy would be a promising strategy to reduce CO2 emissions and produce value-added carbon compounds. However, the development of efficient light-harvesting ...

AACVD Synthesis and Characterization of Iron and Copper Oxides Modified ZnO Structured Films

Abstract: Non-modified (ZnO) and modified (Fe2O3@ZnO and CuO@ZnO) structured films are deposited via aerosol assisted chemical vapor deposition. The surface modification of ZnO with iron or copper oxides is achieved in a second aerosol assisted chemical vapor deposition step and the characterization of morphology, structure, and surface of these new structured films is discussed. X-ray photoelectron spectrometry and X-ray diffraction corroborate the formation of ZnO, Fe2O3, and CuO and the electron microscopy images show the morphological and crystalline characteristics of these structured films. Static water contact angle measurements for these structured films indicate hydrophobic behavior with the modified structures showing higher contact angles compared to the non-modified films. Overall, results show that the modification of ZnO with iron or copper oxides enhances the hydrophobic behavior of the surface, increasing the contact angle of the water drops at the non-modified ZnO structures from 122° to 135° and 145° for Fe2O3@ZnO and CuO@ZnO, respectively. This is attributed to the different surface properties of the films including the morphology and chemical composition.

Enhanced visible-light-assisted peroxymonosulfate activation on cobalt-doped mesoporous iron oxide for orange II degradation

Abstract: Sulfate radical-based advanced oxidation processes (SR-AOP) have attracted a lot of attention due to their capability and adaptability in wastewater treatment. Although heterogeneous cobalt-based catalysts have been extensively studied and have emerged superior for peroxymonosulfate (PMS) activation, leaching of cobalt is still a major concern. Herein, we report a photo-assisted PMS activation approach using cobalt doped mesoporous iron oxide with exceptional activity and stability up to 7 cycles with very low cobalt leaching (0.5 ppm). The highest activity was obtained by 1 mol % cobalt doped mesoporous iron oxide. Orange II dye was completely degraded by the reactive oxygen species (ROS) generated under visible light irradiation within 1 min. ROS were evaluated using two distinct techniques (Fluorescence probes and Electron Paramagnetic Resonance (EPR). ROS quenching experiments were also used to highlight the dominant pathway. This study correlates the structural and electronic changes induced with cobalt doping to the exceptional activity.

Lithium Iron Oxide (LiFeO2) for Electroreduction of Dinitrogen to Ammonia.

Abstract: Electrochemical nitrogen fixation offers a promising route for sustainable NH3 production, while the rational design of effective and durable electrocatalysts is urgently required for an effective ...

Synthesis and characterization of biogenic iron oxides of different nanomorphologies from pomegranate peels for efficient solar hydrogen production

Abstract: An eco-friendly green synthesis of mesoporous iron oxide (hematite) using pomegranate peels through a low-cost and massive product method was investigated. The mass of pomegranate peels was varied to control the morphology of the produced hematite (Fe2O3). The structures, textures and optical properties of the products were investigated by FTIR, XRD, FE-SEM, and UV–Vis spectroscopy. Three different Fe2O3 morphologies were obtained; Fe2O3(I) nanorod like shape, Fe2O3(II) nanoparticles, and Fe2O3(III) nanoporous structured layer. The bandgap values for Fe2O3 (I), (II) and (III) were 2.71, 2.95, and 2.29 eV, respectively. The newly hematite samples were used as promising photoelectrodes supported on graphite substrate for the photoelectrochemical (PEC) water splitting toward the efficient production of solar hydrogen. The number of generated hydrogen moles was calculated per active area to be 50 μmol h−1 cm−2 for electrode III, which decreased to 15.3 μmol h−1 cm−2 for electrode II. The effects of temperature (30–70 °C) on the PEC behavior of the three electrodes were addressed. Different thermodynamic parameters were calculated for the three electrodes, which showed activation energies of 13.4, 16.8, and 15.2 kJ mol−1, respectively. The electrode stability was addressed as a function of the number of runs and exposure time in addition to electrochemical impedance study. Finally, the conversion efficiency of the incident photon-to-current (IPCE) was estimated under the monochromatic illumination. The optimum value was ∼11% @ 390 nm for Fe2O3(III) electrode.

Effects of initial crystal structure of Fe2O3 and Mn promoter on effective active phase for syngas to light olefins

Abstract: Although it is generally acknowledged that iron carbides are the active phase in Fischer-Tropsch synthesis (FTS), adjusting the formation of active phase and catalytic performance via the initial crystal structure of iron oxides has never been studied. Herein, we take one-dimensional pure phase α-Fe2O3 and γ-Fe2O3 nonporous nanorods to explore the effects of initial crystal phase of Fe2O3 on both formation of active phase and corresponding catalytic performance, in which the influence of diffusion limitation on selectivity can be ignored. In situ characterizations uncovered that the formation of iron carbides with high selectivity of light olefins strongly depends on the initial crystal phase of iron oxide and its induced metal-promoter interaction. Responding to the morphology effect and crystallographic phase effect, Mn located on surface of γ-Fe2O3 nanorods exhibit a low oxidation state due to a strong Fe-Mn interaction. This interaction was beneficial to the formation of C-poor iron carbide species at the metal-promoter interface during carburization. Hence, outstanding selectivity for light olefins (61.2%) was achieved on 0.5 Mn/γ-Fe2O3 nanorods catalyst at a CO conversion of 55.1% under industrially relevant conditions (320 °C, 1 MPa, H2/CO ratio of 1, and W/F = 5 gcat h mol−1). This finding enriches the fundamental understanding of active phase evolution and promoter effect in STO process and may guide the design of a catalyst with high selectivity.

Sustainable Low-Concentration Arsenite [As(III)] Removal in Single and Multicomponent Systems Using Hybrid Iron Oxide-Biochar Nanocomposite Adsorbents-A Mechanistic Study.

Abstract: Rice and wheat husks were converted to biochars by slow pyrolysis (1 h) at 600 °C. Iron oxide rice husk hybrid biochar (RHIOB) and wheat husk hybrid biochar (WHIOB) were synthesized by copyrolysis of FeCl3-impregnated rice or wheat husks at 600 °C. These hybrid sorbents were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), SEM–energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, physical parameter measurement system, and Brunauer–Emmett–Teller (BET) surface area techniques. Fe3O4 was the predominant iron oxide present with some Fe2O3. RHIOB and WHIOB rapidly chemisorbed As(III) from water (∼24% removal in first half an hour reaching up to ∼100% removal in 24 h) at surface Fe–OH functions forming monodentate ≡Fe–OAs(OH)2 and bidentate (≡Fe–O)2AsOH complexes. Optimum removal occurred in the pH 7.5–8.5 range for both RHIOB and WHIOB, but excellent removal occurred from pH 3 to 10. Batch kin...

Plasma-catalytic conversion of CO2 to CO over binary metal oxide catalysts at low temperatures

Abstract: Non-thermal plasma (NTP) technology is gaining increasing interest for CO2 conversion due to its potential to convert inert and stable CO2 to value-added fuels and chemicals at ambient conditions. Combining catalysts with plasma can enhance conversion and energy efficiency simultaneously, overcoming the trade-off barrier commonly present in plasma processes. This work reports the influence of various ceria-promoted iron oxide catalysts on the decomposition of CO2 to carbon monoxide and oxygen in a packed bed, dielectric barrier discharge (DBD) reactor at low temperatures and ambient pressure. As ceria is an expensive rare earth metal, its combination with a cheap, abundant metal such as iron can make the process far more economical. The optimum CO2 conversion (24.5%) and energy efficiency (13.6%) were achieved using γ-Al2O3 supported 5Fe5Ce, almost twice the conversion attained using 10Fe (13.3%). Catalysts were characterized using N2 adsorption, X-ray diffraction (XRD), Raman spectroscopy, H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) analysis. A solid solution formed from the mixture of iron oxide and ceria. A critical concentration of iron oxide is required to increase the number of oxygen vacancy sites in the solid solution. The synergy between Fe and Ce, and thus the oxygen vacancy sites, can also be optimized via the synthesis method. A reaction mechanism has been proposed for CO2 conversion at the catalyst surfaces.

Preparation of Scalable Silica‐Coated Iron Oxide Nanoparticles for Nanowarming

Abstract: Cryopreservation technology allows long-term banking of biological systems. However, a major challenge to cryopreserving organs remains in the rewarming of large volumes (>3 mL), where mechanical stress and ice formation during convective warming cause severe damage. Nanowarming technology presents a promising solution to rewarm organs rapidly and uniformly via inductive heating of magnetic nanoparticles (IONPs) preloaded by perfusion into the organ vasculature. This use requires the IONPs to be produced at scale, heat quickly, be nontoxic, remain stable in cryoprotective agents (CPAs), and be washed out easily after nanowarming. Nanowarming of cells and blood vessels using a mesoporous silica-coated iron oxide nanoparticle (msIONP) in VS55, a common CPA, has been previously demonstrated. However, production of msIONPs is a lengthy, multistep process and provides only mg Fe per batch. Here, a new microporous silica-coated iron oxide nanoparticle (sIONP) that can be produced in as little as 1 d while scaling up to 1.4 g Fe per batch is presented. sIONP high heating, biocompatibility, and stability in VS55 is also verified, and the ability to perfusion load and washout sIONPs from a rat kidney as evidenced by advanced imaging and ICP-OES is demonstrated.

Effect of asymmetrical heat rise/fall on the film flow of magnetohydrodynamic hybrid ferrofluid.

Abstract: The movement of the ferrous nanoparticles is random in the base fluid, and it will be homogeneous under the enforced magnetic field. This phenomenon shows a significant impact on the energy transmission process. In view of this, we inspected the stream and energy transport in magnetohydrodynamic dissipative ferro and hybrid ferrofluids by considering an uneven heat rise/fall and radiation effects. We studied the Fe3O4 (magnetic oxide) and CoFe2O4 (cobalt iron oxide) ferrous particles embedded in H2O-EG (ethylene glycol) (50–50%) mixture. The flow model is converted as ODEs with suitable similarities and resolved them using the 4th order Runge-Kutta scheme. The influence of related constraints on transport phenomena examined through graphical illustrations. Simultaneous solutions explored for both ferro and hybrid ferrofluid cases. It is found that the magnetic oxide and cobalt iron oxide suspended in H2O-EG (ethylene glycol) (50–50%) mixture effectively reduces the heat transfer rate under specific conditions.

Hematite iron oxide nanoparticles (α-Fe2O3): Synthesis and modelling adsorption of malachite green

Abstract: To study themalachite green(MG) removal from aqueous solution, iron oxide was prepared from iron(III) nitrate nonahydrate (Fe(NO3)3, 9H2O) and ammonium hydroxide (NH4OH). The Fe2O3characterizationwas examined by X-ray diffraction spectroscopy (XRD), Brunauer Emmett- Teller (BET) specific surface area measurements and Fourier transform infrared (FT-IR) spectroscopy. The data of malachite green Kinetics adsorptions, show that the adsorption followed pseudo-second order kinetics. For concentrations below 6.10−4 mol/l, MG solution was almost completely decolorized after 45 min. The elimination percentage reached 86.13% for the concentration 6.10−4 mol/l and 25 mg of the Hematite. The experimental isotherms were analyzed with Langmuir, Freundlich and Redlich–Peterson using non-linear regression. The results showed that the Freundlich isotherms best-fit the equilibrium data. The thermodynamic study has shown that MG adsorption on Hematite is endothermic (ΔH°>0); it increases with temperature. The negative ΔG° values showed that the MG adsorption process on the Hematite is spontaneous. However, the positive value of ΔS° indicates the increase in Hematite-solution interface disorder at the time of MG fixation.

Green synthesis of Fe 2 O 3 nanoparticles using fruit extract of Cornus mas L. and its growth-promoting roles in Barley

Abstract: Iron oxide nanoparticle fabrications have gained increasing attention owing to their vital role in industrial application. Taking green synthesis of nano-products into account, this experiment was conducted to provide a simple, facile, economic, and fast procedure for the biosynthesis of Fe2O3 nanoparticles using fruit extracts of Cornelian cherry. The FTIR spectroscopy revealed that hydroxyl and amino groups have the ability to perform dual functions of reduction and stabilization of iron oxide nanoparticles. XRD analysis manifested the crystal structure of the Fe2O3 nanoparticle. The SEM image of synthesized Fe2O3 nanoparticle demonstrated the morphology of nanoparticles is spherical. Transmission electron microscopy (TEM) images showed very fine spherical Fe2O3 nanoparticles ranging from 20 to 40 nm. The EDXRF spectra displayed only iron and oxygen elements, which implies that the sample is highly pure Fe2O3 nanoparticle. The Fe2O3 nanoparticle and its bulk form at the concentrations ranging from 10 to 100 mg L−1 showed statistically significant stimulation in both root and shoot biomass. However, Fe2O3 nanoparticle was more effective than the bulk to stimulate barley growth. The findings may be functionalized in the production and formulations of nano-based fertilizers.

Micro-structure and optical spectroscopy of PVA/iron oxide polymer nanocomposites

Abstract: The current research aims to synthesize and investigate the optical spectroscopy of PVA/iron polymer nanocomposites. The polymer films prepared via dissolving powders and characterized by XRD, SEM and optical spectroscopy measurements. The analysis of XRD depicted the cubic crystal structure of γ-Fe2O3 nanoparticles with average crystallite size 42.40 nm. SEM monographs provided the complete interaction between γ-Fe2O3 and PVA polymer matrix. Optical absorption measurements of the PVA/iron oxide polymer nanocomposites displayed a red shift of the absorption edge with the iron oxide content. The optical indirect energy gaps estimated from optical absorption data decreased from 5.0 to 2.4 eV with the iron oxide content. In addition, the refractive index values enhanced with the concentration of iron oxide. Comparing the energy gap values estimated from Tauc's formula and optical dielectric loss function confirmed the major electronic transitions as direct allowed. The fluorescence spectra of the PVA/iron polymer nanocomposites displayed emission peaks centered at 421, 451 and 469 nm and the intensity reduced with the ratio of iron oxide.

Rates and Microbial Players of Iron-Driven Anaerobic Oxidation of Methane in Methanic Marine Sediments

Abstract: The flux of methane, a potent greenhouse gas, from the seabed is largely controlled by anaerobic oxidation of methane (AOM) coupled to sulfate reduction (S-AOM) in the sulfate methane transition (SMT). S-AOM is estimated to oxidize 90 % of the methane produced in marine sediments and is governed by a consortium of anaerobic methanotrophic archaea (ANME) and sulfate reducing bacteria. An additional methane sink, i.e., iron oxide coupled AOM (Fe-AOM), has been suggested to be active in the methanic zone of marine sediments. Geochemical signatures below the SMT such as high dissolved iron, low to undetectable sulfate and high methane concentrations, together with the presence of iron oxides are taken as prerequisites for this process. So far, neither has Fe-AOM been proven in marine sediments nor have the governing key microorganisms been identified. Here, using a multidisciplinary approach, we show that Fe-AOM occurs in iron oxide-rich methanic sediments of the Helgoland Mud Area (North Sea). When sulfate reduction was inhibited, different iron oxides facilitated AOM in long-term sediment slurry incubations but manganese oxide did not. Especially magnetite triggered substantial Fe-AOM activity and caused an enrichment of ANME-2a archaea. Methane oxidation rates of 0.095 ± 0.03 nmol cm 3 d 1 attributable to Fe-AOM were obtained in short-term radiotracer experiments. The decoupling of AOM from sulfate reduction in the methanic zone further corroborated that AOM was iron oxide-driven below the SMT. Thus, our findings prove that Fe-AOM occurs in methanic marine sediments containing mineral-bound ferric iron and is a previously overlooked but likely important component in the global methane budget. This process has the potential to sustain microbial life in the deep biosphere.