MnFe2O4 Nanoparticles Research Articles

The modified biochar from wheat straw by the combined composites of MnFe2O4 nanoparticles and chitosan Schiff base for enhanced removal of U(VI) ions from aqueous solutions.

In the last few decades, U(VI) is a significant environmental threat. The innovative and environmentally friendly adsorbent materials for U(VI) removal were urgent. Preparation of the modified biochar from wheat straw by combined composites of MnFe2O4 nanoparticles and chitosan Schiff base (MnFe2O4@CsSB/BC) was characterized, and adsorption experiments were carried out to investigate the performance and interfacial mechanism of U(VI) removal. The results showed that MnFe2O4@CsSB/BC exhibited high adsorption capacity of U(VI) compared with BC. The adsorption process of U(VI) removal by MnFe2O4@CsSB/BC could be ascribed as pseudo-second-order model and Langmuir model. The maximum adsorption capacity of U(VI) removal by MnFe2O4@CsSB/BC reached 19.57mg/g at pH4.0, 30mg/L of U(VI), and 25°C. The possible mechanism was a chemical adsorption process, and it mainly contained electrostatic attraction and surface complexation. Additionally, it also was an economic and environmental friendly adsorbent.

Effect of structural optimization of magnetic MnFe2O4@Bi24O31Br10/Bi5O7I with core-shell structure on its enhanced photocatalytic activity to remove pharmaceuticals

Pharmaceutical contamination spreading across the aquatic environment has resulted in great disturbance to ecosystem and severe menace to human health. Magnetic photocatalysts have achieved great attention due to their magnetic separation capacity, recycling usage and low risk for secondary pollution. However, their practical applications to solve pollution problem are limited due to the insufficient photocatalytic activity, which is caused by their low valence band potentials and fast recombination of photo-generated carriers. In our research, by involvements of layer-structured bismuth-rich oxyhalides (BixOyXz, X = Cl, Br, I), optimizations for the microstructure and band structure of magnetic MnFe2O4 were applied to improve its photocatalytic activity for effectively removing pharmaceuticals residues. With the assistance of Bi24O31Br10 and Bi5O7I, MnFe2O4 nanoparticles (NPs) was gradually optimized to core-discontinuous shell structure of MnFe2O4@Bi24O31Br10 (M@B) and multi-layer entire core-shell structure of MnFe2O4@Bi24O31Br10/Bi5O7I (M@B/B). The optimized microstructures of M@B and M@B/B provide tight contact between components and promote the separation and utilization rates of carriers in photocatalytic process. For ternary M@B/B, tight contact between the components permits the working of optimized band structure, where double-Z scheme is formed and a favorable electron transfer mode is allowed. The production rates of active radicals from CB of Bi5O7I and VB of MnFe2O4 and Bi24O31Br10 are promoted and their redox abilities are strengthened. The synergy of improved utilization rate of carriers and their strengthened redox ability endows M@B/B with superior photocatalytic performance for removing pharmaceuticals with high concentrations. The removal efficiencies of M@B/B are determined to be 93.2%, 95.0% and 87.8% in 100 min for levofloxacin (LVFX, 20 mg L−1), tetracycline (TC, 50 mg L−1) and triclosan (TCS, 100 mg L−1), respectively. Our research provides a novel and effective channel to improve the photocatalytic activity of magnetic materials by involvements of BixOyXz compounds. According to its enhanced photocatalytic performance, suitable magnetic separation capacity and recycling usage, the practical applications of MnFe2O4 magnetic composites to treat real pharmaceuticals wastewater are reasonable and realistic.

Evaluation of structural, optical, and magnetic properties of Gd doped MnFe2O4 nanoparticles

In this study, the MnFe2O4 doped Gd (MnGdxFe2-xO4 with x = 0, 0.125, 0.25, and 0.5) magnetic nanoparticles were successfully synthesized and revealed the significant effect of Gd content on structural, optical, and magnetic properties. The replacement of Fe3+ ions by ion Gd3+ ions changed the crystallite size from 8.2 nm (x = 0) to 13.5 nm (x = 0.5). The band gap of Gd-doped MnFe2O4 increased with an increase of the x value. The magnetic curves showed that saturation magnetization (MS) and magnetic anisotropy (K) decreased simultaneously with the concentration of Gd3+ ions. The MS value reduced from 54.0 emu/g (MnFe2O4) to 35.4 emu/g (MnGd0.5Fe1.5O4). The K value dropped from 50.4 kJ/m3 (MnGd0.125Fe1.875O4) to 12.3 kJ/m3 (MnGd0.5Fe1.5O4). The substantial reliance of magnetic anisotropy on the doping concentration, namely this large change in K with a little change in size (8.2 nm–13.5 nm), demonstrated that doping is a suitable method for modifying the values of magnetic anisotropy of materials.

Multifunctional MnFe2O4/TiO2/Ti3C2Tx composites based on in-situ grown TiO2 for efficient microwave absorption, high hydrophobicity, and heat dissipation properties

Despite the fact that the 2D structure Ti3C2Tx with abundant defects and functional groups contributes to the high microwave absorption (MA) performance, it is difficulty to improve the strength and bandwidth by pursuing higher conductivity or loading more groups due to the limitation of intrinsic properties. Therefore, it is important to ingeniously design efficient Ti3C2Tx based MA composites assembling the features of abundant surface groups, good dispersibility, multiple composition, and precise structure. Inspired by the fact that Ti3C2Tx contains thermodynamically metastable marginal Ti atoms, TiO2 nanoparticles can be grown in-situ on Ti3C2Tx nanosheets uniformly and increase the spacing of Ti3C2Tx layers, and then MnFe2O4 nanoparticles are introduced into the layers of Ti3C2Tx by electrostatic self-assembly method for optimized impedance matching. This designed hierarchical MnFe2O4/TiO2/Ti3C2Tx composites shows excellent MA performance, and the minimum reflection loss (RLmin) reaches −46.91 dB with a thickness of 2.5 mm at frequency of 10.4 GHz. The high MA performance mainly comes from the enhanced interfacial polarization induced by edges location and interface region among TiO2, MnFe2O4, and Ti3C2Tx. In addition, the conduction loss existed in the interior untreated Ti3C2Tx, the dielectric loss generated by multiple composition, the multiple scattering from improved large surface specific area all contribute to the excellent MA performance. Meanwhile, the simple preparation process and good stability storage at room temperature under air atmosphere of the MnFe2O4/TiO2/Ti3C2Tx composites promote its exploration on practical use, and the lab-gown cloth coated with MnFe2O4/TiO2/Ti3C2Tx composites shows better electromagnetic shielding properties, hydrophobicity, and heat transfer ability than pure fabric, showing the potential for practical application.

Enhanced Photocatalytic Performance of g‐C3N4@MnFe2O4 Nanocomposite for Crystal Violet Dye Degradation under Solar Light

AbstractCrystal violet (CV) dye has been used in the textile industry, as printing ink, biological stain, and antimicrobial agent. CV dye persists in water for a long time and poses a serious threat to humans and aquatic life. In this study, g‐C3N4, MnFe2O4 nanoparticles, and g‐C3N4@MnFe2O4 (80 : 20 wt %) nanocomposite were synthesized via thermal decomposition and chemical co‐precipitation routes. The crystallite size was found 36.31 nm and 30 nm for bare MnFe2O4 nanoparticle and g‐C3N4@MnFe2O4 nanocomposite respectively. The optical band gaps of MnFe2O4, g‐C3N4, and g‐C3N4@MnFe2O4 were 1.8 eV, 2.7 eV, and 2.4 eV, respectively. The photoluminescence intensity decreases in the following order: g‐C3N4>g‐C3N4@MnFe2O4 nanocomposite>MnFe2O4. The degradation efficiency of MnFe2O4, g‐C3N4, and g‐C3N4@MnFe2O4 nanocomposite was found to be 25.13 %, 58.11 %, and 98.42 % respectively, and followed first‐order kinetics. The value of the rate constant for g‐C3N4@MnFe2O4 was 0.022 min−1 which was around ten times higher than g‐C3N4 and MnFe2O4. By adding three scavengers, the degradation capacity of nanocomposite was decreased in the order AA (L‐ascorbic acid)>EDTA (ethylenediaminetetraacetic acid)>TBA (t‐butyl alcohol). A slight reduction in degradation efficiency was observed after five consecutive cycles. Thus, this new finding can be applied to the degradation of CV dye‐contaminated industrial wastewater under solar light.

Development of an analytical strategy for the determination of trace lead in hibiscus tea extract by double slotted quartz tube assisted flame atomic absorption spectrometry after manganese ferrite based dispersive solid phase extraction

In this study, a manganese ferrite (MnFe2O4) based dispersive solid phase extraction method (MF-DSPE) was proposed for the determination of lead (Pb) ions in hibiscus tea by double slotted quartz tube flame atomic absorption spectrometry (SQT-FAAS). The MnFe2O4 nanoparticles used as sorbent were produced in high yields using a green and friendly microwave synthesis procedure. The limit of detection (LOD) was found to be 14.2 µg/L under the optimal conditions. Recovery experiments were performed to assess the applicability of the developed method using hibiscus tea as test sample matrix. High recovery results were obtained by applying the matrix matching calibration method. Thanks to the developed MF-DSPE-SQT-FAAS method, the detection sensitivity for lead was improved by about 108-folds according to the comparison of the slopes of the calibration plots of the FAAS and MF-DSPE-SQT-FAAS systems.

Chitosan/Alginate Nanogels Containing Multicore Magnetic Nanoparticles for Delivery of Doxorubicin.

In this study, multicore-like iron oxide (Fe3O4) and manganese ferrite (MnFe2O4) nanoparticles were synthesized and combined with nanogels based on chitosan and alginate to obtain a multimodal drug delivery system. The nanoparticles exhibited crystalline structures and displayed sizes of 20 ± 3 nm (Fe3O4) and 11 ± 2 nm (MnFe2O4). The Fe3O4 nanoparticles showed a higher saturation magnetization and heating efficiency compared with the MnFe2O4 nanoparticles. Functionalization with citrate and bovine serum albumin was found to improve the stability and modified surface properties. The nanoparticles were encapsulated in nanogels, and provided high drug encapsulation efficiencies (~70%) using doxorubicin as a model drug. The nanogels exhibited sustained drug release, with enhanced release under near-infrared (NIR) laser irradiation and acidic pH. The nanogels containing BSA-functionalized nanoparticles displayed improved sustained drug release at physiological pH, and the release kinetics followed a diffusion-controlled mechanism. These results demonstrate the potential of synthesized nanoparticles and nanogels for controlled drug delivery, offering opportunities for targeted and on-demand release in biomedical applications.

A chemodynamic nanoenzyme with highly efficient Fenton reaction for cancer therapy

Chemodynamic therapy (CDT) is a rising technology for cancer therapy by converting intracellular hydrogen peroxide (H2O2) into hydroxyl radical (•OH) via transition-metal-containing nanoparticles (NPs) catalysis reaction (i.e. Fenton reaction) to kill tumor cells. Highly efficient Fenton reaction and favorable delivery of the catalytic NPs ‘nanoenzyme’ are the key for successful treatment of cancer. In this work, we developed a novel nanoenzyme MnFe2O4@GFP for in vitro and in vivo antitumor therapy. A new MnFe2O4 nanoparticle containing two transition-metal-element Fe and Mn was synthesized for enhanced Fenton reaction and used to co-deliver protein with high biocompatibility through post-modification with dopamine polymerization, green fluorescent protein adsorption, and PEG coating. The enrichment of H2O2 and glutathione (GSH) in tumor tissue provided a favorable microenvironment for in situ generation of toxic free radicals. Fe3+ and GSH triggered a redox reaction to produce Fe2+, which in turn catalyzed H2O2 into •OH, with the consumption of antioxidant GSH. By combining Fe3+ with another catalyzer, the catalytic efficiency of the nanoenzyme were greatly improved. Consequently, the nanoenzyme showed efficient antitumor ability both in vitro and in vivo. Thus, the multifunctional CDT nanoenzyme platform shows great promising for antitumor therapy through the combination of catalyzers Fe3+ and Mn2+ and codelivery of protein cargo.

Efficacy of Carbon Nanodots and Manganese Ferrite (MnFe2O4) Nanoparticles in Stimulating Growth and Antioxidant Activity in Drought-Stressed Maize Inbred Lines.

Despite being the third most-consumed crop, maize (Zea mays L.) is highly vulnerable to drought stress. The predominant secondary metabolite in plants is phenolic acids, which scavenge reactive oxygen species to minimize oxidative stress under drought stress. Herein, the effect of carbon nanodots (CND) and manganese ferrite (MnFe2O4) nanoparticles (NP) on the drought stress tolerance of maize has been studied. The experimental results revealed that the highest leaf blade length (54.0 cm) and width (3.9 cm), root length (45.2 cm), stem diameter (11.1 mm), root fresh weight (7.0 g), leaf relative water content (84.8%) and chlorogenic (8.7 µg/mL), caffeic (3.0 µg/mL) and syringic acid (1.0 µg/mL) contents were demonstrated by CND-treated (10 mg L-1) inbred lines (GP5, HW19, HCW2, 17YS6032, HCW3, HCW4, HW7, HCW2, and 16S8068-9, respectively). However, the highest shoot length (71.5 cm), leaf moisture content (83.9%), shoot fresh weight (12.5 g), chlorophyll content (47.3), and DPPH free radical scavenging activity (34.1%) were observed in MnFe2O4 NP-treated (300 mg L-1) HF12, HW15, 11BS8016-7, HW15, HW12, and KW7 lines, respectively. The results indicate that CND and MnFe2O4 NP can mitigate drought stress effects on different accessions of the given population, as corroborated by improvements in growth and physio-biochemical traits among several inbred lines of maize.

Pd-doped flower like magnetic MnFe2O4 spinel ferrit nanoparticles: Synthesis, structural characterization and catalytic performance in the hydrazine-borane methanolysis

MnFe2O4 nanoparticles, an important member of nanostructured transition metal oxides, also known as spinel ferrites, find wide use in many applications, especially medicine and catalysis, due to their fascinating properties. In this research article, MnFe2O4 and MnFe2O4 supported Pd0 nanoparticles were primarily prepared by solvothermal and impregnation/reduction methods, respectively. After the structural and morphological examination of the MnFe2O4 decorated Pd0 nanoparticles (Pd@MnFe2O4), their catalytic activity was tested in the release of hydrogen from the methanolysis of hydrazine-borane. The morphological characterizations of Pd@MnFe2O4 catalyst show that Pd0 nanoparticles were successfully decorated (average particle size ∼2.83 nm) on the flower-like MnFe2O4 spinel ferrite nanoparticles. The Pd@MnFe2O4 catalyst presented high catalytic performance in the H2 production via the methanolysis of hydrazine-borane, and the turn-over frequency value at 298 K was 47.2 min−1, which is the highest catalytic systems in the literature for this purpose. The Pd@MnFe2O4 catalyst displaying good activity in ten consecutive catalytic runs can be considered a good heterogeneous catalyst for the hydrogen production from the methanolysis of hydrazine-borane.

A Strategy for Tuning the Structure, Morphology, and Magnetic Properties of MnFe2O4/SiO2 Ceramic Nanocomposites via Mono-, Di-, and Trivalent Metal Ion Doping and Annealing.

This work presents the effect of monovalent (Ag+, Na+), divalent (Ca2+, Cd2+), and trivalent (La3+) metal ion doping and annealing temperature (500, 800, and 1200 °C) on the structure, morphology, and magnetic properties of MnFe2O4/SiO2 ceramic nanocomposites synthesized via sol-gel method. Fourier-transform infrared spectroscopy confirms the embedding of undoped and doped MnFe2O4 nanoparticles in the SiO2 matrix at all annealing temperatures. In all cases, the X-ray diffraction (XRD) confirms the formation of MnFe2O4. In the case of undoped, di-, and trivalent metal-ion-doped gels annealed at 1200 °C, three crystalline phases (cristobalite, quartz, and tridymite) belonging to the SiO2 matrix are observed. Doping with mono- and trivalent ions enhances the nanocomposite's structure by forming single-phase MnFe2O4 at low annealing temperatures (500 and 800 °C), while doping with divalent ions and high annealing temperature (1200 °C) results in additional crystalline phases. Atomic force microscopy (AFM) reveals spherical ferrite particles coated by an amorphous layer. The AFM images showed spherical particles formed due to the thermal treatment. The structural parameters calculated by XRD (crystallite size, crystallinity, lattice constant, unit cell volume, hopping length, density, and porosity) and AFM (particle size, powder surface area, and thickness of coating layer), as well as the magnetic parameters (saturation magnetization, remanent magnetization, coercivity, and anisotropy constant), are contingent on the doping ion and annealing temperature. By doping, the saturation magnetization and magnetocrystalline anisotropy decrease for gels annealed at 800 °C, but increase for gels annealed at 1200 °C, while the remanent magnetization and coercivity decrease by doping at both annealing temperatures (800 and 1200 °C).

Zn- doped MnFe2O4 nanoparticles for magnetic hyperthermia and their cytotoxicity study in normal and cancer cell lines

To improve magnetic hyperthermia for the treatment of cancer, we prepared Mn1−xZnxFe2O4 (x = 0.1, 0.3, 0.4, & 0.5) magnetic nanoparticles (NPs) using the solvothermal reflux method. The preparation of NPs single phase was confirmed by X-ray diffraction (XRD) investigation. The prepared sample's magnetic properties were greatly improved by the addition of Zn, increasing its magnetization value. The specific loss power (SLP) values in DI water were used to assess the performance of the colloids. Zn0.1Mn0.9Fe2O4 NPs displayed the highest SLP value among the samples, at 1 mg/mL concentration (107.79 W/g) in an alternating magnetic field (AMF) of 35.2 kA/m and 316 kHz. This proved how effectively they could produce heat for magnetic hyperthermia therapy. Through cell cytotoxicity analysis, the cytotoxicity of the Zn-doped MnFe2O4 NPs was evaluated, and the results showed high biocompatibility and negligible cytotoxicity. This shows that the NPs are appropriate for biomedical applications, particularly in the treatment of cancer with magnetic hyperthermia. The better magnetic characteristics and effective heat generation for hyperthermia treatment were obtained through the synthesis of Zn-doped MnFe2O4 NPs. The NPs also showed great biocompatibility, making them viable options for biomedical applications, particularly in the treatment of cancer.

MnFe2O4 nanoparticles coated on one-dimensional carbon nanowires derived from Nitrilotriacetic acid as efficient catalysts to activate peroxymonosulfate for moxifloxacin degradation

Sulfate radical-based advanced oxidation processes (AOPs) are highly reliable for the elimination of recalcitrant contaminants by increasing degradability and reducing toxicity. Here, MnFe2O4 nanowires (MnFe2O4 NWs), composed of abundant MnFe2O4 nanoparticles immobilized on one-dimensional carbon nanowires derived from annealed MnFe-Nitrilotriacetic acid (MnFe-NTA) precursor was successfully synthesized. The MnFe2O4 NWs, which could provide more active sites, were then utilized to activate peroxymonosulfate (PMS) for oxidizing the target pollutant Moxifloxacin (MOX) in an aqueous solution. The MnFe2O4 NWs/PMS system acquired 91.9% removal of MOX and achieved 55.1% chemical oxygen demand (COD) degradation efficiency in 30 min. The results exhibited that the increased catalyst doses and PMS concentration lead to ascending MOX removal rate, which decreased with the participation of co-existing ions. Besides, there is a close relationship between original pH and MOX degradation efficiency. It was found that SO4⋅–, ⋅OH, 1O2, and O2⋅– were involved in the MOX degradation by quenching experiments and electron paramagnetic resonance (EPR) detection. More importantly, the stable magnetism of MnFe2O4 NWs contributed to its convenient recycling. Finally, a reliable mechanism for activating PMS was proposed based on the aforementioned results and previous researches, which could exhibit a novel horizon in effluent treatment.

Removal of nitrobenzene from aqueous solution using manganese ferrite nanoparticles

Magnetic manganese ferrite (MnFe2O4) nanoparticles were successfully synthesized via a chemical co-precipitation route. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopies (SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and N2 adsorption-desorption isotherms. MnFe2O4 nanoparticles showed effective adsorption of nitrobenzene from an aqueous solution. The Langmuir and D-R models were well-described adsorption isotherms. The maximum adsorption capacity (qmax) of nitrobenzene onto MnFe2O4 was found to be 64.37 mg/g. The pseudo-second model was the most suitable for the fitting of the experimental kinetic data. The equilibrium adsorption capacity (qe) of MnFe2O4 was 50 mg/g. Thermodynamics data showed nitrobenzene adsorption was spontaneous, and exothermic, with decreased randomness. The regeneration cycle showed that the prepared sample has 80% adsorption capacity after five times adsorption–desorption cycles. MnFe2O4 nanoparticles can be used as a low-cost alternative to commercial for the adsorption of nitrobenzene from an aqueous solution.

Immobilized acetylcholinesterase in magnetic nanoparticles for in-line inhibition studies using a capillary electrophoresis system

Enzyme assays can be performed with the capillary electrophoresis technique (CE) in many approaches, such as the immobilized enzyme micro-reactor. Acetylcholinesterase is a promising enzyme to be used when pursuing such a method, as it has already been explored in the proposal of similar methods of miniaturizing enzyme assays. The present work proposes a novel enzyme micro-reactor, based on the anchorage of the enzyme on magnetic nanoparticles of MnFe2O4, with chitosan and glutaraldehyde as the cross-linker in the capillary by means of an arrange of neodymium magnets. The calculated Km of the enzyme evaluated by this method was 1.12 mmol L−1, comparable to other studies in the literature that utilizes immobilized enzymes. Also, IC50 for neostigmine was assessed in 3 different micro-reactors, with an average of 29.42 ± 3.88 μmol L−1. In terms of the micro-reactor stability, it was possible to perform at least 25 experiments with assembled micro-reactor. The method was applied to hydroalcoholic extracts of 7 plant species. Plinia cauliflora had the best result, with 42.31 ± 6.81% of enzyme inhibition in a concentration of 100 mg L−1.

Nigella sativa-Manganese Ferrite-Reduced Graphene Oxide-Based Nanomaterial: A Novel Adsorbent for Water Treatment.

In this study, a novel nanohybrid composite was fabricated via the incorporation of manganese ferrite (MnFe2O4) nanoparticles into the integrated surface of reduced graphene oxide (rGO) and black cumin seeds (BC). The nanohybrid composite was prepared by a simple co-precipitation method and characterized by several spectroscopic and microscopic techniques. The characterization analysis revealed that the rGO-BC surface was decorated with the MnFe2O4. The strong chemical interaction (via electrostatic and H-bonding) between the integrated surface of rGO-BC and MnFe2O4 nanoparticles has been reported. The prepared composite was highly porous with a heterogeneous surface. The average size of the prepared composite was reported in the ranges of 2.6-7.0 nm. The specific surface area of the prepared composite was calculated to be 50.3 m2/g with a pore volume of 0.061 cc/g and a half pore width of 8.4 Å. As well, many functional sites on the nanohybrid composite surface were also found. This results in the excellent adsorption properties of nanohybrid composite and the effectual elimination of methylene blue dye from water. The nanohybrid was tested for various linear isotherms, such as Langmuir and Freundlich, for the adsorption of methylene blue dye. The Freundlich isotherm was the well-fitted model, proving the adsorption is multilayer. The maximum Langmuir adsorption capacity of nanohybrid composite for methylene blue was reported to be 74.627 mg/g at 27 °C. The adsorption kinetics followed the pseudo-second-order recommended surface interaction between the dye and nanohybrid composite. The interaction between methylene blue and the nanohybrid composite was also confirmed from the FTIR spectrum of the methylene blue-loaded adsorbent. The rate-determining step for the present study was intraparticle diffusion. Temperature-dependent studies of methylene blue adsorption were also carried out to estimate adsorption's free energy, enthalpy, and entropy. The methylene blue adsorption was feasible, spontaneous, and endothermic. A comparison study revealed that the present materials could be successfully prepared and used for wastewater treatment.

Magnetic properties and self‐heat behaviors of core@shell structured MnFe2O4@Fe3O4 magnetic nanoparticles

AbstractIn this work, a facile solvothermal synthesis of MnFe2O4 nanoparticles is followed by an easy and reproducible process to envelop the synthesized MnFe2O4 nanoparticles with iron oxide nanoparticles using ethanol and ethylene glycol as solvents. All prepared MnFe2O4 nanoparticles show a homogenous distribution of spherical particles with an average particle size between 12 and 16 nm. The encapsulation process of MnFe2O4 nanoparticles does not affect their homogenous distribution with a very thin layer of Fe3O4 on the shell structure. The magnetic properties showed a superparamagnetic character with enhanced magnetic properties of MnFe2O4@Fe3O4 compared to pure MnFe2O4, which has been verified by magnetization and electron spin resonance. The heating efficiency of the prepared samples was evaluated in terms of the specific loss power using the calorimetric method. The synthesized MnFe2O4 nanoparticles show a significantly high value of about 72 W/g, which got doubled in the core@shell structure and reached 140 W/g at 189 kHz and 10kA/m of the magnetic field.

Graphene oxide–MnFe2O4 nanohybrid material as an adsorbent of Congo red dye

The aim of this work is the synthesis and characterization of graphene oxide (GO)–MnFe2O4 nanohybrid material, as well as the study of its performance in the removal of Congo red (CR) dye from aqueous solutions. The GO–MnFe2O4 was prepared via a three-step method. Firstly, GO was produced via a modified Hummers' method, using graphite powder as starting material. Subsequently, GO was functionalized with ionic surfactants, cetyltrimethylammonium bromide and poly(sodium-4-styrenesulfonate). Following this, the functionalized GO was decorated with magnetic MnFe2O4 nanoparticles via an electrostatic self-assembly process using a solvothermal treatment at 200 °C for 12 h. The as-prepared GO–MnFe2O4 nanohybrid material was characterized by several techniques: X-ray diffraction analysis, Fourier-transform infrared spectroscopy, micro-Raman spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, and high-resolution transition electron microscopy with energy-dispersive spectroscopy mapping. The adsorption performance of GO–MnFe2O4 in the removal of CR dye was evaluated at different initial CR concentrations and contact times using an ultraviolet–visible spectrophotometer. In addition, its recyclability performance was investigated for 10 cycles. It is noteworthy that even after the last cycle, the removal efficiency of GO–MnFe2O4 exceeded 65%, indicating that the adsorbent had very good reusability. Finally, the Freundlich isotherm model yielded a better fit for the adsorption data, compared to Langmuir, while adsorption of CR by GO–MnFe2O4 showed pseudo-second-order kinetics.

Effect of post annealing process on structural, magnetic and spin dynamics properties of MnFe2O4 nanoparticles

The present research work focuses on the one-step and cost-effective hydrothermal synthesis and characterization of manganese ferrite (MnFe2O4) magnetic nanoparticles (MNPs). To investigate the effect of different annealing temperatures on the structural, magnetic and spin dynamics properties of the as-synthesized MNPs, samples were annealed at 200°C, 400°C, and 600°C. X-ray diffraction (XRD) analysis showed that all samples had a cubic spinel phase structure with space group Fd-3 m (227), with minor impurities of α-Fe2O3 and α-Mn2O3 phase are present. The average crystallite size of the MNPs increased with increasing annealing temperature, due to grain growth. The molecular dynamics, bond stretching, and cubic spinel phase of all samples were analyzed through IR spectroscopy. Furthermore, the post-annealing process resulted in a decrease in saturation magnetization from 44.04 emu/g to 29.01 emu/g, which increased to 33.79 emu/g as the annealing temperature was raised from 200°C to 400°C and further to 600°C. Ferromagnetic resonance spectroscopy was utilized to validate the magnetic characteristics, unveiling the presence of unpaired electrons and assessing the resonant magnetic field, g-factor and peak-to-peak line width.The broad resonance signal observed in the room temperature spin dynamics indicated a strong dipolar-dipolar interactions interaction between magnetic ions through oxygen ions. The obtained results indicate that the synthesized MnFe2O4 MNPs have the potential to be used in various biomedical applications, including targeted drug delivery and magnetic hyperthermia treatment, owing to their biocompatibility, excellent magnetic properties, and facile synthesis method. This study paves the way for further research on the applications of MnFe2O4 MNPs in the field of nanomedicine.

Magnetic MnFe2O4 nanoparticles anchored on sludge-derived biochar in activating peroxydisulfate for levofloxacin degradation: Mechanism, degradation pathways and cost analysis

The sludge-derived biochar (SBC) was prepared by a low-cost microwave pyrolysis process, and then MnFe2O4 nanoparticles were anchored onto the surface of SBC through a hydrothermal route to construct a magnetic MnFe2O4/SBC composite catalyst. As-obtained MnFe2O4/SBC catalysts were characterized by XRD, FT-IR, Raman, FE-SEM, BET surface area and XPS. The optimized MnFe2O4/SBC(1:3) catalyst showed a higher catalytic activity to activate peroxydisulfate (PDS) for levofloxacin (LVF) degradation than that of SBC, MnFe2O4 and reported magnetic composite catalysts. After 80 min of reaction, 79.5% of LVF in water (10 mg/L) was degraded by MnFe2O4/SBC(1:3) in the presence of PDS (1.5 g/L), and LVF degradation followed the pseudo-second-order kinetics. Calcium carbonate (CaCO3) in SBC participates in PDS activation. XPS analysis, oxidative species capture experiments, EPR and linear sweep voltammetry (LSV) tests confirmed that LVF degradation in MnFe2O4/SBC-PDS oxidation system was achieved through the non-radical (electron transfer, 1O2) and radical (SO4•−, ∙OH and O2•−) pathways, with the former playing a dominant role. The degradation routes of LVF were established based on the degradation intermediates. LVF removal efficiency from real water matrices was improved by means of increasing catalyst dosage and reaction temperature. Cost analysis indicates that MnFe2O4/SBC-PDS oxidation process is a cost-effective method to eliminate the antibiotics in water.