Formation Of ZnFe2O4 Research Articles

Visible light driven ZnFe2O4 for the degradation of oxytetracycline in the presence of HSO5− at semi-pilot scale and additional H2 production

This study investigated the synthesis of visible light driven ZnFe2O4 for photocatalytic degradation of oxytetracycline (OTC) in a continuous flow reactor and production of hydrogen (H2). OTC is widely used as a medication and found to create severe health and environmental issues. The use of advanced characterization techniques proved successful formation of ZnFe2O4 which was found to be reusable, stable, highly crystalline, and nano-sized. The prepared ZnFe2O4 caused 60% removal of OTC and removal efficiency of the latter was promoted to 85% by adding HSO5– with ZnFe2O4 at 240 min employing reactor flow rate of 0.1 L/min and concentrations of ZnFe2O4, OTC, and HSO5– as 1.0 g/L, 20 mg/L, and 100 mg/L, respectively. The addition of HSO5– was found to give hydroxyl radical (•OH) and sulfate radical (SO4•−) and the latter caused degradation of OTC into degradation products. The removal of OTC was promoted by factors facilitating the rate of formation of •OH and SO4•−. The ZnFe2O4 proved effective in photocatalytic H2 production and showed H2 production rate of 23.4 μmol h−1 g−1. The results suggest that ZnFe2O4 could be used as an economically viable technology for emerging pollutants degradation and green energy production.

Thermodynamic analysis of zinc ferrite (ZnFe2O4) formation inside the HIsarna off-gas system

ABSTRACT HIsarna reactor is characterized by a high raw materials versatility and is therefore attractive for processing secondary iron sources. Among the materials that can be recycled through HIsarna, zinc-bearing material has drawn a special attention. Based on the plant data, once dust-containing Zinc was injected into the main reactor, a final collected dust with a zinc content of 16% was achieved which opened up possibilities of higher enrichment for direct reuse in Zn smelting as a secondary source and an alternative for Zn ore (the primary source). However Zn vapor can react with iron oxide to form zinc ferrite (ZnFe2O4), which is an undesired product. Hence, the main focus of this study is to minimize the formation of ZnFe2O using thermodynamic (FactSage) and computational fluid dynamic tools. After detecting regions with high potential of ZnFe2O4 formation, proper geometrical and operational modifications of the off-gas system is proposed to minimize the formation of zinc ferrite.

MOF-derived magnetically recoverable Z-scheme ZnFe2O4/Fe2O3 perforated nanotube for efficient photocatalytic ciprofloxacin removal

Constructing advanced direct Z-scheme photocatalysts is an effective strategy to enhance photogenerated charge separation for photocatalytic removal of organic pollutants but faces challenges in efficient morphology control and recovery method. Herein, a novel magnetically recoverable Z-scheme ZnFe2O4/Fe2O3 perforated nanotube was successfully prepared by one-step MOF-derived calcination method by using MIL-88B/Zn core/shell nanorod as precursor for the first time. In the calcination process, MIL-88B core reacted with oxygen to form hollow Fe2O3 and Zn2+ shell underwent an in situ solid-state reaction with Fe2O3 to cause volume shrinkage and formation of ZnFe2O4, and finally turned into intimate ZnFe2O4/Fe2O3 perforated nanotube (ZFF). Because of such exquisitely perforated nanotube and Z-scheme transfer pathway, ZFF shows superior light absorption, bulk-phase and interfacial separation of photogenerated charge, and thus lead to prominent photocatalytic performance for ciprofloxacin (CIP) removal. Especially, ZFF-2 exhibits the best photocatalytic CIP degradation performance with a degradation percentage of 96.5% and a TOC removal percentage up to 89% under light irradiation for 180 min. Moreover, ZFF show sufficient photo-stability and re-usability for photocatalytic degradation of CIP by a convenient magnetic recovery method. The electron spin resonance experiments, radical trapping and fluorescence experiments reveal that the photogenerated charge pathways of ZFF photocatalysts is a Z-scheme mechanism and the major active species for degradation of CIP are •O2– and •OH. This work offers a new perspective on construction of high-efficient direct Z-scheme photocatalysts with convenient recovery and deep insight on pollutants purification mechanism.

Incorporation of Fe and Cu for antibacterial performance enhancement of Fe-Cu-ZnO nanocomposites synthesized by a facile chemical precipitation

Fe-Cu-ZnO nanocomposites were synthesized using simple chemical precipitation under a violent stirring condition, and characterized by dynamic light scattering, ultraviolet-visible spectroscopy, scanning electron microscopy, X-ray diffractometry, Raman spectroscopy, and vibrating sample magnetometer. The particle size distribution is observed not only a large size of 100 nm to 2 mm, but also a small size of 0.4-5.0 nm. The absorbance peaks of the nanocomposites exhibit a small blue shift in comparison with ZnO. Surface defects are explored in the nanocomposites including irregular shapes, rough surfaces, and aggregation. The nanocomposites and ZnO have similar hexagonal wurtzite structures. However, the nanocomposites have more crystal defects than ZnO due to ZnFe2O4 formation. Although the presence of zinc ferrite (ZnFe2O4) is also detected, magnetic hysteresis is disappeared because of poor ZnFe2O4 distribution and critical size effects. In antibacterial test, the nanocomposites were applied to inhibit the growth of Xanthomonas campestris, Pseudomonas aeruginosa, and Pseudomonas fluorescens. It is found that antibacterial performance is enhanced relating to surface and crystal defects. These defects are possible to increase interfacial contacts and accelerate antibacterial activities for the antibacterial enhancement. Therefore, the Fe-Cu-ZnO nanocomposites are alternative potential material appropriately for bacterial inhibition application.

Preparation of ZnFe2O4/ZnO composite: Effect of operational parameters for photocatalytic degradation of dyes under UV and visible illumination

An ZnFe2O4/ZnO composite catalyst was prepared by solution combustion method. In this study, one nominal molar percentage of iron was used in the synthesis, corresponding to 20 % molar relative to ZnO. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray Fluorescence (XRF), Scanning Electronic Microscopy (SEM), Transmission Electronic Microscopy (TEM) and Ultraviolet-visible (UV–vis) diffuse spectroscopy (DRS). The photocatalytic activities of the catalysts were investigated based on the degradation of two dyes, methylene blue (MB) and remazol brilliant blue (RBB), in aqueous solution under both UV and visible light illumination respectively. It was found that the composite had a good photocatalytic activity at basic pH by using 1 g/L of catalyst under UV illumination for both MB and RBB. Under visible illumination, while pristine ZnO showed no activity, the composite exhibited an excellent visible efficiency, reaching up to an 80 % conversion of the initial dye concentrations in 2 h. The enhancement of the visible photocatalytic activity of Fe/ZnO sample with respect to pristine ZnO is attributed to the formation of ZnFe2O4 coupled with ZnO, having a narrow band gap value that contributes to the absorption of visible photons with an improved separation path for the photo-generated carriers.

The impact of polyol structure on the formation of Zn0.6Co0.4Fe2O4 spinel-based pigments

The formation of Zn0.6Co0.4Fe2O4 spinel-based pigments by sol–gel method and post-annealing pathway and the impact of polyol structure on their properties were investigated. The phase evolution and mass changes of gels during annealing were assessed by thermal analysis. The differential thermal analysis revealed that above 400 °C the carboxylate precursors decompose to ZnFe2O4, CoFe2O4, and Zn2SiO4. X-ray diffraction pattern showed the presence of crystalline ZnFe2O4, CoFe2O4, Zn2SiO4, and SiO2, while Fourier transform infrared spectra confirmed the formation of metal-carboxylates and SiO2 matrix at 200 °C and formation of ZnFe2O4, CoFe2O4, and Zn2SiO4 at 1200 °C. The atomic force microscopy images showed spherical nanoparticles of size and shape varying with the polyol structure. The coloring properties and the potential ceramic applications of the obtained dark gray powders were tested by their embedding in opaque and transparent tile glazes and their application on ceramic tile.

Normal spinel structure ZnFe2O4/g-C3N4 enhanced catalytic activity for photo-Fenton degradation of methylene blue

Heterogeneous photo-Fenton technology has been widely employed to degrade organic dyes in wasterwater. In the present study, a composite consisting of normal spinel structure ZnFe2O4 nanoparticle and two-dimensional sheet of g-C3N4 was facilely synthesized. Different characterization technologies, such as XRD, XPS and VSM, were employed to demonstrate the normal spinel structure ZnFe2O4 formation. The composite shows higher catalytic activity for degradation of methylene blue (MB) than mixed spinel structure ZnFe2O4/g-C3N4. Simultaneously, the composite exhibits excellent stability and reusability.

Shape-controlled synthesis of superparamagnetic ZnFe2O4 hierarchical structures and their comparative structural, optical and magnetic properties

Herein, we report a prospective strategy to synthesize ZnFe2O4 hierarchical structures assembled by nanoparticles to obtain different morphology like spheres, rods, and flowers. The morphological influence on physicochemical and magnetic properties has been extensively explored. Phase purity of samples was determined by X-ray diffraction (XRD) and morphological and structural features were elucidated with the help of field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) with energy dispersive spectroscopy (EDX) tool was used for elemental analysis. FESEM and HRTEM confirmed the formation of ZnFe2O4 with different morphologies. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy gave the insight of bonding mechanism associated with the synthesized materials. Meanwhile, the material chemistry of obtained products was investigated by X-ray photoelectron spectroscopy (XPS). The surface area of samples with different morphologies have also been found to vary from 19 to 55.8 m2/g while the optical band gap study confirmed that nanorods have smaller band gap having value 2.86 eV when compared to sphere and flower structures with band gap 4 eV and 3.47 eV respectively. Magnetic measurements performed on vibrating sample magnetometer (VSM) ascertains the superparamagnetic behavior of synthesized materials.

Effect of preparation methods on the structure and catalytic performance of Fe–Zn/K catalysts for CO 2 hydrogenation to light olefins

Abstract Potassium promoted iron–zinc catalysts prepared by co-precipitation method (C–Fe–Zn/K), solvothermal method (S–Fe–Zn/K) and hydrothermal method (H–Fe–Zn/K) could selectively convert CO2 to light olefins, respectively. The physicochemical properties of the obtained catalysts were determined by SEM, N2 physisorption, XRD, H2-TPR, CO2-TPD and XPS measurements. The results demonstrated that preparation methods had great influences on the morphology, phase structures, reduction and adsorption behavior, and hence the catalytic performance of the catalysts. The samples prepared by hydrothermal and co-precipitation method generated small uniform particles and led to lower specific surface area. In contrast, microspheres with larger specific surface area were formed by self-assembly of nanosheets using solvothermal method. ZnFe2O4 was the only detectable phase in the fresh C–2Fe–1Zn/K, S–3Fe–1Zn/K and S–2Fe–1Zn/K samples. ZnFe2O4 and ZnO co-existed with increasing Zn content in S–1Fe–1Zn/K sample, while ZnO and Fe2O3 could be observed over H–2Fe–1Zn/K sample. All the used samples contained Fe3O4, ZnO and Fe5C2. The peak intensity of ZnO was strong in the AR-H–2Fe–1Zn/K sample while it was the lowest in the AR-C–2Fe–1Zn/K sample after reaction. The formation of ZnFe2O4 increased the interaction between iron and zinc for C–2Fe–1Zn/K and S–Fe–Zn/K samples, causing easier reduction of Fe2O3 to Fe3O4. The surface basicity of the sample prepared by co-precipitation method was much more than that of the other two methods. During CO2 hydrogenation, all the catalysts showed good activity and olefin selectivity. The CO selectivity was increased with increasing Zn content over S–Fe–Zn/K samples. H–2Fe–1Zn/K catalyst preferred to the production of C5+ hydrocarbons. CO2 conversion of 54.76% and C2=–C4= contents of 57.38% were obtained on C–2Fe–1Zn/K sample, respectively.

Thermal-induced magnetic transition in CoFe2O4@ZnO

Composites of CoFe2O4 and ZnO (CFO@ZnO) nanomaterials were synthesized using double stage co-precipitation. The structural properties have been investigated by x-ray diffraction which shows the presence of hexagonal ZnO and spinel CoFe2O4. Variation in lattice parameters, after annealing at elevated temperature, indicates the diffusion of cations from the ZnO to CoFe2O4 and vice versa. Magnetic properties were measured by Mössbauer spectroscopy and superconducting quantum interference device magnetometer. The transition from ferrimagnet to paramagnet at 973 K is due to the formation of ZnFe2O4. High quadrupole splitting values in Mössbauer spectra depict the presence of interstitial Co defects. The Co cations diffuse in the ZnO lattice in the course of annealing at 1273 K, forming CoxZn1−xO resulting in ferromagnetism.

Enhanced Photocatalytic Degradation of 17α-Ethinylestradiol Exhibited by Multifunctional ZnFe2 O4 -Ag/rGO Nanocomposite Under Visible Light.

In this paper, ZnFe2 O4 , a visible light active photocatalyst, was comodified by graphene oxide (GO) and Ag nanoparticles (NPs) to form ZnFe2 O4 -Ag/rGO nanocomposite (NC) by facile one-pot hydrothermal method. Reduction of GO and formation of ZnFe2 O4 and Ag nanoparticles occurred simultaneously during hydrothermal reaction. The photocatalytic activity of the NC was investigated under visible light, for the degradation of 17α-ethinylestradiol (EE2), a nondye compound, which also is an emerging pollutant with endocrine-disrupting activity. The pseudo rate constant (k') of as-synthesized ZnFe2 O4 -Ag/rGO NC was higher by the factor of 14.6 and 5.6 times than the corresponding ZnFe2 O4 and ZnFe2 O4 /rGO respectively. The synergistic interactions between ZnFe2 O4 , Ag and rGO leading to decreased aggregation of the NPs, increased surface area, better absorption in visible region, effective electron-hole generation transfer. However, in the presence of humic acid (HA), the photosensitization effect was predominated by competitive interaction resulting in only 80% removal of EE2 within the same time. Moreover, the composite can easily be magnetically separated for reuse.

Ferromagnetic Behavior in Zinc Ferrite Nanoparticles Synthesized using Coprecipitation Technique

Zinc ferrite have been produced and used by humans since long time, however understanding of ZnFe2O4 as a nano structured materials is very useful in order to be used for technological applications. ZnFe2O4 structural, magnetic and electrical properties are different when synthesized using different techniques. Therefore, it would be interesting to investigate the structural and magnetic properties of ZnFe2O4 when in nanosize. In the present work nanocrystalline ZnFe2O4 was synthesized using coprecipitation technique. The structural and magnetic properties of ZnFe2O4 nanopowders were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), dynamic light scattering (DLS), infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The XRD of ZnFe2O4 nanoparticles showed the single phase spinel structure. The average particle size of ZnFe2O4 calculated from XRD was observed to be 45 nm. DLS measurements showed the average particle size to be 42 nm. Further, the phase formation of ZnFe2O4 was confirmed from the IR measurements. The IR spectra showed the bands corresponding to ZnFe2O4. We observed the room temperature ferromagnetic behavior in synthesized ZnFe2O4 nanoparticles which may be due to the random distribution of Zn2+ and Fe3+ at the tetrahedral (A) and octahedral [B] sites. In our future work, we want to investigate the defect induced magnetic properties of ZnFe2O4 nanoparticles which is likely to contribute for ferromagnetic behavior in this material.

Formation of the ZnFe2O4 phase in an electric arc furnace off-gas treatment system

To better understand the phenomena of ZnFe2O4 spinel formation in electric arc furnace dust, the dust was characterized with particle size analysis, X-ray fluorescence (XRF), electron backscatter diffraction (EBSD), and electron probe micro-analysis (EPMA). Different ZnFe2O4 formation reaction extents were observed for iron oxide particles with different particle sizes. ZnO particles were present as both individual particles and aggregated on the surface of larger particles. Also, the slag particles found in the off-gas were shown not to react with the zinc vapor.After confirming the presence of a ZnFe2O4 formation reaction, the thermodynamic feasibility of in-process separation – a new electric arc furnace dust treatment technology – was reevaluated. The large air intake and the presence of iron oxide particles in the off-gas were included into the thermodynamic calculations. The formation of the stable ZnFe2O4 spinel phase was shown to be thermodynamically favorable in current electric arc furnace off-gas ducts conditions even before reaching the post combustion chamber.

Structure and magnetic properties of Ni0.64Zn0.36Fe2O4 nanoparticles synthesized by high-energy milling and subsequent heat treatment

High energy ball milling and subsequent annealing were applied to synthesize nanocrystalline Ni0.64Zn0.36Fe2O4 ferrite from a powder mixture of pure metal Zn, Fe2O3 and NiO in an oxygen atmosphere. The structural and phase evolution of powder particles after different milling times were studied by X-ray diffractometry. The XRD results showed that a Ni–Zn ferrite was formed with some residual Fe2O3 by annealing a 30-h-milled sample at as low as 400 °C for 2 h. The average crystallite size of the 30 h-milled powder was estimated to be about 15 nm which grew to 21 nm after annealing at 500 °C for 2 h. TEM image showed an agglomerated state of particles for 30 h-milled powders. FT-IR analysis indicated two absorption bands in the Ni–Zn ferrite structure related to octahedral and tetrahedral sites, respectively, in the range of 400–600 cm−1. Thermogravimetric analysis showed a mass loss about 2 % for as-received powder mixture below 400 °C; after that, it was almost stable. The Ni–Zn ferrite formation mechanism was detected to be in three stages: oxidation of zinc, diffusion of ZnO in Fe2O3 and the formation of ZnFe2O4, and diffusion of NiO in ZnFe2O4 and the formation of Ni–Zn ferrite. Vibrating sample magnetometery results revealed that a saturation magnetization of the 30 h-milled sample was about 5 emu/g which increased to 16 emu/g after annealing at 400 °C due to a reduction in density of lattice imperfections and strain.

Facile synthesis of stoichiometric zinc ferrite nanocrystal clusters with superparamagnetism and high magnetization

Stoichiometric ZnFe2O4 magnetic nanocrystal clusters (MNCs) with an average diameter of 127nm have been successfully synthesized by using a one-step solvothermal method without any additives, where nitrates (Fe(NO3)3 and Zn(NO3)2) were used as reactants. Different characterization techniques were used, such as XRD, ICP-AES, TEM, HRTEM, XPS, and SQUID. The results demonstrate that the stoichiometric ZnFe2O4 is superparamagnetic, and the saturation magnetization (35.9±0.1emu/g at 300K, 78.0±0.1emu/g at 5K) is higher than that reported in some references. However, when FeCl3 and ZnCl2 were used as reactants that replaced the nitrates at the same experimental conditions, ZnFe2O4·40Fe3O4 was synthesized. The NO3− decreased the Fe2+ concentration through oxidation and reduction reactions in the polyol method for the formation of ZnFe2O4. A possible mechanism for the stoichiometric ZnFe2O4 formation was proposed and discussed, based on the time-resolved experiments.

Structural and magnetic properties of transition metals doped ZnO(TM)/ZnO multilayers

ZnO(Fe)/ZnO multilayers (MLs) with Fe 6.5% (Fe-doped sample) and ZnO(FeNi)/ZnO MLs with Fe22Ni78 6.5% (Ni-doped sample) prepared by helicon plasma sputtering were investigated. Structures of as-prepared Fe- and Ni-doped samples show the layer structures and the ZnO crystalline structures. However, the samples annealed at 773 K induced the formation of ZnFe2O4 for Fe doped sample, and the growth of metallic Ni for Ni-doped sample. Furthermore, Fe atoms in the annealed Fe-doped sample are dispersed mainly in the surface region, and Ni atoms in as-prepared and annealed Ni-doped samples are located uniformly in the film. The ionic states of Fe in Fe-doped sample and Ni in Ni-doped sample before and after annealing are the mixed Fe2+/3+ and metallic Ni, respectively. Therefore, it is considered that the as-prepared and the annealed Ni-doped samples form Ni particles. As-prepared samples showed the paramagnetic properties. However, the magnetic state of the as-prepared Ni-doped sample is partly superparamagnetic due to the existence of small Ni particles. On the other hand, annealed samples show the ferromagnetic characteristics due to formation of ZnFe2O4 for Fe-doped ones and growing metallic Ni particles for Ni-doped ones.

Synthesis of ZnFe2O4 nanoparticles and their asymmetric configuration with Ni(OH)2 for a pseudocapacitor

Nanosized zinc ferrite (ZnFe2O4) particles are prepared by a simple aspartic acid assisted combustion method at three different pH conditions. X-ray diffraction analysis (XRD) is used to identify the single phase formation of ZnFe2O4 and its crystal system. The particle size and shape are revealed through transmission electron microscopy (TEM) images and the particles are in the size range between 20–30 nm. The valence states of zinc, iron and oxygen are determined through X-ray photoelectron spectroscopy (XPS). The electrochemical performances of the individual electrodes and fabricated cells are studied using cyclic voltammetry (CV), galvanostatic charge–discharge analysis (GCD) and impedance spectroscopy (EIS) analysis. A maximum specific capacitance of 1235 F g−1 at 1 mA cm−2 is obtained for ZnFe2O4 prepared at pH 10. Furthermore an asymmetric supercapacitor (ASC) is fabricated using ZnFe2O4 as the negative electrode and Ni(OH)2 as the positive electrode. Interestingly, this assembled ASC delivers good energy and power densities of 33 W h kg−1 and 68 W kg−1, respectively.

Fabrication of a Ternary Hybrid Semiconductor ZnFe2O4/CdS-TiO2 NTs Structure on the Ti-5Zr Alloy

ZnFe2O4 and CdS nanoparticles were loaded onto TiO2 nanotubes (NTs) formed on Ti-5Zr alloy. The ZnFe2O4 and CdS nanoparticles were obtained by electrodeposition and chemistry bath deposition (CBD) methods, respectively. For the electrodeposition of Fe-Zn alloys, transitional steady current density decreased while the concentration of Zn ion in the electrolyte increased. Meanwhile, Fe/Zn ion ratio in the electrolyte determined the composition of Fe-Zn alloys; optimum electrodeposited Fe-Zn alloys for ZnFe2O4 formation were obtained by tuning the deposition variables. The mean diameters of ZnFe2O4 and CdS were about 160 nm and 25 nm, respectively. Study on scanning electron microscopy (SEM), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) indicated that the prepared samples were highly ordered TiO2 NTs composite with ZnFe2O4 and CdS nanoparticles loading on.

Self-assembly of a ZnFe2O4/graphene hybrid and its application as a high-performance anode material for Li-ion batteries

A nanohybrid based on ZnFe2O4 nanospheres and graphene nanosheets (ZnFe2O4/G) has been synthesized by a facile one-pot in situ solvothermal route. The results show that the formation of ZnFe2O4 and the reduction of graphite oxide take place simultaneously during the solvothermal reactions. Spheric ZnFe2O4 nanoparticles with a size of 100–200 nm are confined in between the graphene sheets, forming a unique hybrid nanostructure. The electrochemical measurements have shown that the ZnFe2O4/G hybrid exhibits improved electrochemical Li-storage properties compared with bare ZnFe2O4, due to the combined buffering, confining and conducting effects of the in situ introduced graphene nanosheets.

Structural and magnetic properties of epitaxial Fe3O4/ZnO and ZnO/Fe3O4 bilayers grown on c-Al2O3 substrate

In the present work, we report the growth and properties of pulsed laser deposited epitaxial bilayer structures of Fe3O4/ZnO and ZnO/Fe3O4 on single crystal Al2O3 (0001) substrates. In order to check the structural compatibility of these structures we annealed these samples at different temperatures. Interface between the two layers plays an important role in determining the structural and magnetic properties. X-ray diffraction (XRD) studies revealed the (111) and (0001) oriented growth of Fe3O4 ZnO layers, respectively, in both the bilayers. Phi-scan shows the epitaxial nature of individual layer in both the bilayers. Raman spectra and XRD indicate the formation of ZnFe2O4 at the interface after annealing of ZnO/Fe3O4 bilayer. Magnetization measurements are in correlation with the structural results. The results indicate that Fe3O4/ZnO bilayer is more stable and has sharper interface than the other bilayer.