Fe3O4 Magnetite Nanoparticles Research Articles

Photocatalytic degradation of naproxen using TiO2 single nanotubes

Herein, TiO2 single-tube (TiO2 ST-NT) powders with and without magnetite Fe3O4 nanoparticles (TiO2 ST-NT@Fe3O4NPs) are presented for the first time as excellent photocatalysts for the degradation of one of the most popular non-steroidal anti-inflammatory drugs (NSAIDs), naproxen (NPX). The TiO2 ST-NT powders were synthesized by anodization followed by etching of the double wall, bending, sonication, ultra-centrifugation, and finally annealing at 600°C. A part of the obtained TiO2 ST-NT powders was decorated with Fe3O4 nanoparticles using a simple one-step decoration process. The best photocatalytic performance of TiO2 ST-NT and TiO2 ST-NT@Fe3O4NPs powders was obtained under the white light (6.2 × 10−4 s-1) and the blue light (2.7 × 10−4 s-1), respectively. During NPX photodegradation using TiO2 ST-NT powders, three main NPX transformation products (P1, P2, and P3) were detected. Upon excitation with the blue light illumination, TiO2 ST-NT@ Fe3O4NPs powders exhibited higher performance (∼80%) than TiO2 ST-NT powders (∼23%) within 1 h, resulting in an approximately three times increased photocatalytic rate constant. Moreover, under simulated sunlight conditions, TiO2 ST-NT powders demonstrated remarkable activity, achieving a 94% NPX degradation within 1 h. TiO2 ST-NT and TiO2 ST-NT@Fe3O4NPs powders represent excellent photocatalysts for NPX degradation.

Green Synthesis of Magnetite Nanoparticles Using <i>Moringa oleifera</i> and their Electro-Optic Surface Plasmon Resonance Properties

The application of an external electric field to the surface plasmon resonance (SPR) system of green-synthesized magnetite (Fe3O4) nanoparticles (MNPs) is very promising for increasing the SPR detection signal. Electro-optic surface plasmon resonance (EOSPR) behavior of MNPs has been successfully carried out. The EOSPR system was investigated using the Kretschmann configuration with the prism/Au thin film/MNPs/air layer arrangement and applying an electric voltage of 0 V, 2 V, 4 V, and 6 V. In this study, we synthesized MNPs using the green synthesis approach from moringa oleifera extract. The benefits of green synthesis include being safe, affordable, clean, and ecologically friendly processes. X-ray diffraction results obtained crystal size of the MNPs is about 9.2 nm with inverse spinel face-centered cubic crystal structure. Fourier transforms infrared characterization showed the presence of Fe-O bonds at wave numbers 569 cm-1 and 629 cm-1, indicating that MNPs were successfully formed. The saturation magnetization of the samples is 55.3 emu/g. The SPR angle of the SPR system Prism/Au thin film/air without the addition of MNPs is 44.66°. After being deposited by MNPs and induced by a voltage of 0 V, 2 V, 4 V, and 6 V, the SPR angles changed to 44.87°, 44.90°, 44.95° and 45.12°. The addition of MNPs and an external electric field causes the SPR angle to increase. The results of this study can provide new insights into the development of optical devices that can be manipulated electrically and have the potential for future biosensor applications.

IMMOBILIZATION AND STUDY OF TRYPSIN ON MAGNETITE-Fe3O4 NANOPARTICLE-BASED NATURAL AND SYNTHETIC POLYMER HYDROGELS

The presented article designs hydrogel structures with magnetite nanoparticles in the composition, involving various synthetic and natural polymers. The synthesis of magnetite nanoparticles in the hydrogel composition was accomplished through the co-precipitation method, and the immobilization of protein using trypsin as a model drug was investigated. The incorporated of micro-quantities of magnetite Fe3O4 nanoparticles into the gel matrix enhances the affinity for the enzyme, resulting in a significant improvement in specific activity and stability compared to gels without magnetite Fe3O4 nanoparticles. In other words, increasing the degree of immobilization of magnetite Fe3O4 nanoparticles enhances both the immobilization degree and the biological activity of the enzyme. This phenomenon manifests as a continuous interaction between the gel composition and the magnetite nanoparticles of the enzyme

Iron Oxide (Magnetite)-Based Nanobiomaterial with Medical Applications-Environmental Hazard Assessment Using Terrestrial Model Species.

Nanobiomaterials (NBMs) have tremendous potential applications including in cancer diagnosis and treatment. However, the health and environmental effects of NBMs must be thoroughly assessed to ensure safety. Fe3O4 (magnetite) nanoparticles coated with polyethylene glycol (PEG) and poly (lactic-co-glycolic acid) (PLGA) were one of the focus NBMs within the EU project BIORIMA. Fe3O4 PEG-PLGA has been proposed to be used as a contrast agent in magnetic resonance imaging for the identification of solid tumors and has revealed low cytotoxicity in several cell lines. However, the effects of Fe3O4 PEG-PLGA have not been assessed in terrestrial environments, the eventual final sink of most materials. In the present study, the effects of Fe3O4 PEG-PLGA and its precursor, (un-coated) Fe3O4 NMs, were assessed in soil model invertebrates Enchytraeus crypticus (Oligochaeta) and Folsomia candida (Collembola). The endpoints were survival, reproduction, and size, based on the standard OECD test (28 days) and its extension (56 days). The results showed no toxicity for any of the endpoints evaluated, indicating that the NBM Fe3O4 PEG-PLGA poses no unacceptable risk to the terrestrial environment.

Computational analysis of entropy generation minimization and heat transfer enhancement in magnetohydrodynamic oscillatory flow of ferrofluids

Improvements in heat transfer rate and entropy generation minimisation are critical issues in many engineering and industrial applications where efficient heat transfer is essential to achieve optimal performance and lower energy consumption. This study investigates the entropy generation of the mixed convection flow of ferrofluids in the presence of viscous and Joule dissipation. The flow is oscillatory and induced by the sinusoidal oscillations of a flat plate in its plane. Two Newtonian fluids, namely, kerosene oil C12H26C15H32 and methanol CH3OH are considered base fluids containing magnetite Fe3O4 nanoparticles. Governing equations are first modelled by employing the fundamental laws of transport phenomena. Then, using scaling analysis, these equations are transformed into a dimensionless system of partial differential equations. Numerical simulations are performed using the Gear-Generalized Differential Quadrature Method (GGDQM), and the model is validated with special cases from the literature. It has been found through numerical analysis that the convergence of GGDQM can be guaranteed by using only a small number of grid points. The thermal boundary layer of methanol-based nanofluid is thicker than that of kerosene. It has been observed that the skin friction coefficient increases for both categories of nanofluids as the values of the Eckert number, solid volume fraction, and Grashof number increase. The Nusselt number increases as the solid volume fraction increases, while the opposite trend is observed when the values of the Hartman, Eckert, and Grashof numbers rise. With increasing values of the Grashof number, the rise in the velocity of methanol-based nanofluids is higher than that of kerosene oil-based nanofluids. The maximum percentage difference between the velocities is identified to be 22.2177% at Gr=4.0. The temperature of methanol-based nanofluids rises more quickly than that of kerosene oil-based nanofluids with increasing values of the Grashof number. It is determined that the largest percentage difference between the temperatures is 20.5968% at Gr=4.0. When Ec=0, the percentage difference between velocities is 29. 1721 %, while the percentage difference between temperatures is 78.7155%. Compared to methanol-based ferrofluid, the volumetric entropy production is more extensive in kerosene-based ferrofluid. On the other hand, in comparison to a kerosene-based nanofluid, thermal irreversibility predominates in a methanol-based nanofluid. The novelty of this study lies in the computational treatment of coupled partial differential equations (momentum and energy) that incorporate buoyancy force, Joule heating and viscous dissipation effects, complementing the underlying physics and mathematical modelling of the research problem.

Facile microwave-assisted preparation of Fe3O4 nanoparticles supported on carbonized cellulose nanocrystals derived from sugarcane bagasse

Microwave energy is an efficient form of energy used to speed up the synthesis of nanoparticles. Herein, we report the use of an unmodified domestic microwave oven to prepare magnetic spherical Fe3O4 (magnetite) nanoparticles (IONPs) supported on carbonized cellulose nanocrystals, forming a nanocomposite, in an expeditious and facile one-step reaction. This was achieved using the readily available precursors of FeCl3 as an iron source, and sugarcane bagasse, using activated charcoal as a microwave absorber. The nanocomposite was characterized using Raman spectroscopy which suggested a degree of crystallinity based on a G/D ratio of 1.25. The morphology of the Fe3O4/carbonized cellulose nanocrystal nanocomposite was characterized as spherical metallic nanoparticles supported on carbonized cellulose nanocrystals using Transmission electron microscopy (TEM), SEM, and EDX, while the identity of the Fe3O4 nanoparticles was confirmed with powder XRD.Graphical

Polyethylene Glycol (PEG) Coated Magnetite Nanoparticles Prepared by Sol-Gel Method for Biotechnology Applications

Polyethylene glycol (PEG) coatings are developed for magnetite nanoparticles (NPs). The magnetic properties of superparamagnetic type, magnetite Fe3O4 nanoparticles are suitable for biosensing applications. Magnetic NPs were prepared by Co-precipitation method and oven dried. Using a Transmission Electron Microscope (TEM) and X-Ray Diffractometer (XRD), nanoparticles size and composition were found, including the presence of Fe3O4 peak. The magnetic properties are influenced by electron environments of the Fe3+ ions within the iron oxide structure. The magnetic properties were measured by Vibrating Sample Magnetometer (VSM), thus, the results of Fe3O4 NPs exhibited a high magnetic saturation (Ms) of 61.31 emu/g. In the case of PEG coated MNPs, confirmed by Fourier Transform Infrared Spectroscopy (FT-IR), a reduced Ms of 40.00 emu/g, which decreased further following surface modification with 3-aminopropyl triethoxysilane (NH2) to 36.77 emu/g. The resulting size range of NPs of pure Fe3O4 NPs was 5-50 nm. In comparison, the PEG coated NPs were larger, 10-100 nm. In the part of protein binding and separation from solutions of bovine serum albumin (BSA) where investigated. This process will be beneficial to developing low cost sensors for biomolecules and biotechnologies in the future.

Effect of dipolar interaction on magnetic properties of magnetite nanoparticles system: a simulation study

Superparamagnetic iron oxide nanoparticles are a potential candidate for novel research. The inter-particle interactions play a significant role in determining the overall magnetic behavior of a magnetic nanoparticle assembly, especially in dipolar interaction. In this paper, we have synthesized a practical sample and then applied an atomistic spin model simulation study with input parameters obtained from experimental measurements to investigate the influence of the dipolar interaction on the magnetic properties of Fe3O4 magnetite nanoparticles.

Efficient magnetic flocculation for microalgae harvesting using a novel composite flocculant of Fe3O4-based starch-grafted-cationic polyacrylamide

As a flocculant for algae harvesting, a novel magnetic starch-grafted-cationic polyacrylamide composite (MAG@ST-g-CPAM) was developed in this study, and the harvesting efficiency of the composite was assessed with comparison to starch, Fe3O4 magnetite nanoparticles, cationic polyacrylamide and starch-grafted-cationic polyacrylamide. The feeding ratios for flocculant synthesis were optimized, and impacting factors were examined. Magnetic particles were recovered for cyclic use, and the effect of MAG@ST-g-CPAM flocculation on water reuse was examined. The results showed that MAG@ST-g-CPAM flocculation successfully achieved harvesting efficiencies of 93.2 % and 97.3 % at doses of 25 mg/L and 30 mg/L, respectively, which were superior to those of other flocculants. The optimized feeding ratio of acrylamide:Fe3O4:starch was 6:4:3. The late exponential algal growth solution with a pH range of 5–6 was most favorable for algae flocculation. A total of 93.7 % of Fe3O4 magnetite nanoparticles was recovered at pH = 3, and flocculation facilitated the reuse of water by effectively eliminating fulvic acids from the culture solution. This study demonstrated that MAG@ST-g-CPAM is a promising flocculant for algae harvesting.

Removal of diazinon from aqueous solutions using alternating current in a three-dimensional electrochemical system containing MC/Fe3O4 nanocomposites

This study aims to determine diazinon removal using a three-dimensional electrochemical system supplied with alternating current (AC), which uses Fe3O4 magnetite nanoparticles immobilized on microbial cellulose (MC). The nanocomposites are used as catalysts to activate persulfate and produce sulfate radicals for diazinon removal. The surface properties and morphology of MC/Fe3O4 nanocomposites were determined by Fourier Transform Infrared Spectroscopy (FT-IR), Field Emission Scanning Electron Microscopes (FE-SEM), Thermo-Gravimetric Analysis (TGA), and X-Ray Diffraction (XRD) techniques. The studied variables were initial pH (3–9), diazinon concentration (10–40 mg/l), persulfate concentration (0.5–0.8 mmol/l), Na2SO4 concentration (0.1–0.7), MC/Fe3O4 nanocomposite concentration (01–0.3 g/l), voltage (1–7 V), and time (0−60). The obtained results indicated that the 3D electrochemical system could lead to complete removal in the presence of the MC/Fe3O4 catalyst in optimal conditions (10 mg/l initial diazinon concentration, 0.5 g/l Na2SO4, pH of 3 ± 0.5, 0.7 mmol/l PS, 0.25 g/l MC/Fe3O4, and 5 V AC) during 60 min. The energy consumption in this system was calculated 0.35 KW h/m3. The role of each process involved in diazinon removal and the reaction kinetics were also provided in this study.

Experimental characterization optimizing the alignment parameter for GNP epoxy base nanocomposite via a weak DC magnetic field

AbstractGraphene has been hailed by scientists as the “wonder material” of the 21st century. Despite the impressive mechanical and electrical qualities of graphene in its unprocessed state, graphene‐based epoxy nanocomposites can only be used as a structural material on a small scale. The random dispersion and orientation of graphene in epoxy cause the failure. Magnetite Fe3O4 nanoparticles are synthesized and solvo‐thermally attached to the graphene nanoplatelets (GNP) surfaces in order to utilize our recently model's suggested optimized alignment parameters. Solution with properly dispersed nanoparticles, that is, Fe3O4‐GNP within epoxy, is exposed to the magnetic field (0.05 T). Morphology, microstructure, and magnetic properties of GNP, Fe3O4, and Fe3O4‐GNP nanoparticles have been characterized by X‐ray diffraction, Fourier‐transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, differential scanning calorimetry, atomic force microscopy, X‐ray photoelectron spectroscopy, Brunauer–Emmett–Teller, transmission electron microscopy, scanning electron microscopy, energy‐dispersive X‐ray microanalysis, and vibrating sample magnetometry. The aforementioned characterization method, optical microscopy, and studying the fracture surface morphology confirmed the alignment. The fabricated aligned Fe3O4‐GNP nanocomposite is best used as a functional material.

Assessing the Heat Generation and Self-Heating Mechanism of Superparamagnetic Fe3O4 Nanoparticles for Magnetic Hyperthermia Application: The Effects of Concentration, Frequency, and Magnetic Field.

Magnetite nanoparticles (MNPs) exhibit favorable heating responses under magnetic excitation, which makes them particularly suited for various hyperthermia applications. Herein, we report the detailed self-heating mechanisms of MNPs prepared via the Ko-precipitation Hydrolytic Basic (KHB) methodology. The as-prepared MNPs were fully characterized using various spectroscopic techniques including transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometry (VSM). MNPs exhibited stable 15 nm quasi-spherical small-sized particles, pure crystalline cubic Fe3O4 phases, high saturation magnetizations (Ms = ~40 emu·g-1), and superparamagnetic behavior. In response to alternating magnetic fields (AMFs), these MNPs displayed excellent self-heating efficiencies with distinctive heating responses, even when minimal doses of MNPs were used. Heating efficacies and specific absorption rate (SAR) values as functions of concentration, frequency, and amplitude were systematically investigated. Remarkably, within only a few minutes, MNPs (2.5 mg/mL) showed a rapid dissipation of heat energy, giving a maximum intrinsic loss power (ILP) of 4.29 nHm2/kg and a SAR of 261 W/g. Hyperthermia temperatures were rapidly reached in as early as 3 min and could rise up to 80 °C. In addition, Rietveld refinement, Langevin, and linear response theory (LRT) models were studied to further assess the magnetic and heating mechanisms. The LRT model was used to determine the Néel relaxation time (τR = 5.41 × 10-7 s), which was compared to the Brownian relation time value (τB = 11 × 10-7 s), showing that both mechanisms are responsible for heat dissipated by the MNPs. Finally, the cytotoxicity assay was conducted on aqueous dispersions of MNPs, indicating their biocompatibility and low toxicity. Our results strongly suggest that the as-prepared Fe3O4 MNPs are promising vehicles for potential magnetically triggered biomedical hyperthermia applications.

Hybrid nanogels by direct mixing of chitosan, tannic acid and magnetite nanoparticles: processes involved in their formation and potential catalytic properties.

Magnetite (Fe3O4) nanoparticles (MNPs) as nanocatalysts have drawn considerable attention because of their unique properties such as peroxidase-like activity. However, their biodistribution and availability for specific treatments still need to be improved. In this study, a simple and convenient strategy for the synthesis of hybrid nanogels (NGs) is described, which involves direct mixing of biomaterials such as chitosan (Ch) and tannic acid (TA), with the incorporation of MNPs, under oxidising conditions, using the inverse nanoemulsion method. The different processes involved in the formation of these hybrid nanosystems as well as their morphological and chemical structure are investigated using optical, spectroscopic, and electron microscopic techniques (DLS, UV-VIS, FT-IR, XPS, TEM, and SEM-EDS). It is demonstrated that ∼11 nm synthesized MNPs, post-functionalized with oxidised TA, act as covalent crosslinkers. As a proof of concept, the potential use of these materials in nanocatalytic medicine was evaluated using a colorimetric method based on the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in hydrogen peroxide. The results show that these hybrid nanogels have the same peroxidase-like activity as bare MNPs, indicating that the organic nanostructure stabilises the inorganic nanoparticles without any significant change in the catalytic properties. Therefore, this kind of nanomaterial has promising potential for use in nanocatalytic medicine with improved biocompatibility and biodistribution.

SYNTHESIS AND STUDY OF STRUCTURES OF MAGNETITE Fe3O4 NANOPARTICLES IN POLYETHYLENE GLYCOL MEDIUM

Synthesis of magnetite Fe3O4 nanoparticles functionalized with polyethylene glycol was carried out by co-precipitation method using a very small amount of organic substances to obtain a highly monodisperse form of nanoparticles, and the structure of obtained Fe3O4 nanoparticles was studied by physical methods. During the synthesis of magnetic Fe3O4 nanoparticles surrounded by a polymer, it has been determined that by adjusting the amount of used polymer, the nature of the precipitating agent, the concentration of the initial precursors and the temperature it was possible to synthesize and stabilize monodisperse Fe3O4 nanoparticles with a high degree of purity, uniform in size

Magnetic Fe/Fe3C@C Nanoadsorbents for Efficient Cr (VI) Removal

Magnetic carbon nanocomposites (α-Fe/Fe3C@C) synthesized employing fructose and Fe3O4 magnetite nanoparticles as the carbon and iron precursors, respectively, are analyzed and applied for the removal of Cr (VI). Initial citric acid-coated magnetite nanoparticles, obtained through the co-precipitation method, were mixed with fructose (weight ratio 1:2) and thermally treated at different annealing temperatures (Tann = 400, 600, 800, and 1000 °C). The thermal decomposition of the carbon matrix and the Fe3O4 reduction was followed by thermogravimetry (TGA) and Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, Raman spectroscopy, SQUID magnetometry, and N2 adsorption-desorption isotherms. A high annealing temperature (Tann = 800 °C) leads to optimum magnetic adsorbents (high magnetization enabling the magnetic separation of the adsorbent from the aqueous media and large specific surface area to enhance the pollutant adsorption process). Cr (VI) adsorption tests, performed under weak acid environments (pH = 6) and low pollutant concentrations (1 mg/L), confirm the Cr removal ability and reusability after consecutive adsorption cycles. Physical adsorption (pseudo-first-order kinetics model) and multilayer adsorption (Freundlich isotherm model) characterize the Cr (VI) absorption phenomena and support the enhanced adsorption capability of the synthesized nanostructures.

PAN—Composite Electrospun-Fibers Decorated with Magnetite Nanoparticles

The results of the synthesis of PAN(polyacrylonitrile)-magnetite composite fibers using the electrospinning method are presented. The electrospinning installation included a rotating drum collector for collecting fibers. Magnetite nanoparticles were synthesized using chemical condensation from an iron chloride solution. It was shown that homogeneous Fe3O4 magnetite nanoparticles with particle sizes of 6–16 nm could be synthesized using this method. Magnetite nanoparticles were investigated using X-ray diffraction analyses and transmission electron microscopy. Based on magnetite nanoparticles, composite PAN/magnetite fibers were obtained through electrospinning. The obtained composite fibers were investigated using scanning electron microscopy, X-ray diffraction analyses, and elemental analyses. It was shown that the magnetite nanoparticles were uniformly distributed on the surface of the fibers. A comparison of PAN fibers without any added magnetite to PAN/magnetite fibers showed that the addition of magnetite led to a decrease in the value of the fiber diameter at the same polymer concentration and under the same electrospinning process conditions.

Influence of synthesis conditions on the structure and size of magnetite nanoparticles in coprecipitation method without stabilizer in one system

The unique properties of magnetite (Fe3O4) nanoparticles (MNPs) have promoted a wide range of applications in various fields, but specifying and defining the preparation conditions of MNPs with the desired monodispersed size are still challenges. This paper discusses systematically the influence of synthesis conditions on the structure and size of MNPs in the coprecipitation method without a stabilizer in one system. The ammonium hydroxide (NH4OH)/iron (III) (Fe3+) ratio, iron (III)/iron (II) (Fe2+) ratio, initial concentration of hydrochloric acid (HCl), total concentration of iron ions, reaction temperature, aging time and washing times were investigated. The surface of magnetite crystals was easily oxidized at high ammonium hydroxide/iron (III) ratios, and the high pH value of the reaction system can induce a large crystalline size. The hydrodynamic diameter of MNPs was efficiently controlled by the equilibrium between Derjaguin–Landau–Verwey–Overbeek (DLVO) forces and non-DLVO forces. An appropriate initial concentration of hydrochloric acid and a higher reaction temperature can reduce the crystalline size due to the decelerated nucleation rate. The aging time and the total concentration of iron affected the crystalline size positively. Noticeably, the pH value of the MNP dispersion in distilled water would remarkably reduce after each washing by centrifugation due to surface absorption of the hydroxy group. This research provided fundamental support for the reproducible preparation of MNPs in the coprecipitation method.

Synthesis of Fe3O4/CNT/ACF cathode-based electro-fenton system for efficient mineralization of methylene blue dye: Kinetics and mechanism

Electro-Fenton (EF) is an innovative process to use in situ generated H2O2 and ∙OH to destruct organic contaminants in wastewater. In this study, methylene blue (MB) was degraded using activated-carbon-felt (ACF) composite cathodes (CNT/ACF, Fe3O4/ACF, and Fe3O4/CNT/ACF). Magnetite (Fe3O4) nanoparticles (MNPs) and carbon nanotubes (CNTs) were used as surface modifiers, i.e., Fe3O4, to facilitate easy charge-transfer by forming multilayered channels and CNTs to enhance the thermal and structural strength of the electrode. When Fe3O4/CNT/ACF was used as cathode, the removal efficiency of 93.7% for MB could be obtained within 1 h; the MB degradation followed the pseudo-second-order kinetics with the rate constant of 2.73 × 10−2 M−1 min−1. Based on total organic carbon (TOC) analysis, 57.8% of MB could be mineralized by the cathode system, which was also confirmed by evaluating the mineralization current efficiency (MCE, kWh m–3). When the EF oxidation time was raised to 2.5 h, MB could be completely degraded while mineralization efficiency was 87%. At 2.5-h degradation time, Fe3O4/CNT/ACF exhibited the highest removal efficiency for color and TOC among the three synthesized electrodes, proving that the cathode has an outstanding catalytic oxidation power for MB degradation with high stability. Thus, the overall study provides an insight for an innovative mechanism of integrating well-performing and easily recyclable electrode composites in an EF system for treating recalcitrant organic pollutants existing in wastewater.

Green synthesis of NiO/Fe3O4@chitosan composite catalyst based on graphite for urea electro-oxidation

In this work, we modified the NiO-based graphite electrode by a green synthesis nanoparticles composite of magnetite@chitosan for urea electrooxidation (UEO) in 0.5 M KOH solution. Green magnetite (Fe3O4) nanoparticles were prepared with green tea extract that acts as a reducing agent. The new composite catalyst Fe3O4@Chitosan performs a dual function to improve the catalytic properties of UEO. The magnetite Fe3O4 nanoparticles increase the active sites by accelerating the electron transfer between Fe3+/Fe2+ions, while chitosan enhances urea adsorption on the electrode surface. Three graphite electrodes were prepared with different NiO and Fe3O4@Chitosan catalysts ratios under optimized conditions and denoted by Ni0.85Fe0.15, Ni0.75Fe0.25, and Ni0.65Fe0.35. The excellent catalytic parameters as maximum current density (35.4 mA cm−2), Tafel slope (69 mVdec−1), diffusion coefficient (5.759 × 10−6 cm2 s−1), and onset potential (446 mV vs. Ag/AgCl) were achieved by Ni0.75Fe0.25 electrocatalyst. The modified NiO/Fe3O4@chitosan electrocatalyst was characterized by XRD and SEM/EDEX-elemental mapping techniques characterized its morphology and chemical structures. Moreover, cyclic voltammetry, double-step Choronoamerometery, and electrochemical impedance were employed to detect the electrodes' catalytic performance. The EIS fitting parameters deduced from R(RQ)& (RQ) equivalent circuits were used to explain how the Ni/Fe ratios' can affect the charge transfer process of UOR at the prepared electrocatalysts surfaces under the applied potentials.

Improvement in desulfurization of dibenzothiophene and dibenzothiophene sulfone by Paenibacillus strains using immobilization or nanoparticle coating.

Biodesulfurization of fossil fuels is a promising technology for deep desulfurization. Previously, we have shown that Paenibacillus strains 32O-W and 32O-Y can desulfurize dibenzothiophene (DBT) and DBT sulfone (DBTS) effectively. In this work, improvements in DBT and DBTS desulfurization by these strains were investigated through immobilization and nanoparticle coating of cells. Paenibacillus strains 32O-W and 32O-Y immobilized in alginate gel beads or coated with Fe3 O4 magnetite nanoparticles were grown at various concentrations (0.1-2 mmol l-1 ) of DBT or DBTS for 96 h. The production of 2-hydroxybiphenyl (2-HBP) from the 4S pathway biotransformation of DBT or DBTS was measured. The highest amounts of 2-HBP production occurred at concentrations of 0.1 and 0.5 mmol l-1 . Compared to planktonic cultures maximum 2-HBP production increased by 54% for DBT and 90% for DBTS desulfurization with immobilized strains, and 44% for DBT and 66% for DBTS desulfurization by nanoparticle-coated strains. Nanoparticle-coated and immobilized cells may be of use in efforts to increase the efficiency of biodesulfurization. Alginate immobilization or nanoparticle coating of bacterial cells may be useful approaches for the enhancement of biodesulfurization for eventual use on an industrial scale.