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This investigation is motivated by the surge of interest in materials, combining high spontaneous magnetization and pseudocapacitance at room temperature. Ferrimagnetic MnFe 2 O 4 offers benefits of high magnetization. However, the non-pseudocapacitive behavior, low capacitance and high resistance of MnFe 2 O 4 are limiting factors for its applications in magnetic pseudocapacitive devices. This investigation demonstrates that nearly ideal pseudocapacitive behavior can be achieved for MnFe 2 O 4 electrodes in Na 2 SO 4 electrolyte. High pseudocapacitance is observed in positive and negative potential ranges and two different charging mechanisms are proposed. High capacitance is achieved at a low impedance. The ability to achieve comparable and high areal capacitances in the positive and negative potential ranges facilitates the fabrication of a symmetric pseudocapacitive device, containing ferrimagnetic MnFe 2 O 4 as cathode and anode material for operation in enlarged voltage window of 1.6 V. The symmetric device shows capacitance of 0.92 F cm−2 at a current density of 3 mA cm−2. The individual electrodes and device show good cycling stability. The approach is based on the use of murexide and gallocyanine as redox-active dispersants and charge transfer mediators. The analysis of testing results provides an insight into the influence of chemical structure, charge and redox properties of the dispersants on the capacitive behavior. The ability to fabricate a pseudocapacitive device, containing two ferrimagnetic electrodes is promising for energy storage, water purification and novel applications based on magnetocapacitive effects. [ABSTRACT FROM AUTHOR]

A series of MnFe2–xYbxO4 powder nanoparticles (for x = 0, 0.025, 0.075, 0.1, and 0.2) of different crystallite sizes were synthesised using the co-precipitation method. The effect of Yb3+ dopant on the properties of manganese ferrite was characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman measurements, and photoluminescence spectroscopy (PL). The crystallite size and density of the samples have a cubic structure with an Fd3m space group. Their sizes and densities were found to be in the range of 24.8–34.7 nm and 5.07–5.49 g/cm3. FT-IR analysis indicates the presence of two absorption bands in the range 400–600 cm–1, which is a fingerprint region of ferrites. The v2 band (Fe–O stretching mode of the octahedral site) shifts towards the lower wavenumber, which confirms the occupancy of larger-size Yb3+ ions at the octahedral site. The Raman peaks were noted at 228, 295, 405, 502, and 634 cm–1 for undoped manganese ferrite. Based on Raman observations, it has been observed that Mn2+ ions exhibit a preference for occupying octahedral (B) sites by substituting Fe3+ ions. Additionally, rare earth ions have been preferentially observed to occupy octahedral sites. The primary cause for the displacement of Raman bands was ascribed predominantly to the greater radii of rare earth ions in comparison with Fe3+ and Mn2+ ions, and the shifting of the peaks indicates the presence of Yb3+ at the octahedral site. The PL spectrum shows emission at 560 nm with a rise in intensity with an increase in dopant Yb3+, which could be because of the incorporation of Yb3+ in the spinel structure, leading to radiative recombination in the yellow region of the electromagnetic spectrum. [ABSTRACT FROM AUTHOR]

For photocatalysis technology to be applied industrially, there has been a significant increase in the need for visible-light-driven photocatalysts that possess exceptional superparamagnetic characteristics to facilitate easy separation. Hence, in this study, rare earth elements (RE) (Sm, Yb, Dy, Er, and Ho) were systematically doped into manganese ferrite (MF) using the coprecipitation method to serve two purposes, namely, reducing the photogenerated electron-hole recombination during photocatalysis and modifying the magnetic properties of MF to become superparamagnetic. The synthesised Re-doped MF was found to be visible light active, as evidenced by the transient photocurrent response and the obtained band gaps, which were in the range of 1.84–1.93 eV. From the cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization plots, it was evident that different RE element dopants have different effects on improving the electrochemical properties of MF. Overall, fast electron transfer of the synthesised materials was found to decrease in the following order: Sm-MF > Dy-MF > Ho-MF > MF > Er-MF > Yb-MF. The g-factor and peak-to-peak line width were found to be in the range of (2.221–2.317) and (93.17–149.85 mT), respectively. The resonance field and hysteresis loop (H c) were found to be in the range of (289.2–301.86 mT) and (8.24–32.61 mT), respectively. Overall, the synthesised RE-doped MF exhibits ferromagnetic properties, and the obtained small H c values hint at these particles exhibiting superparamagnetic properties. In summary, doping MF with Sm, Dy, and Ho is more desirable as it alters the magnetic properties towards superparamagnetic and improves its electrochemical properties. Thus, this study is of importance in advancing the field of photocatalysis in water treatment and material science. • RE (Sm, Dy, Ho, Er, and Yb) were successfully incorporated into the MF spinel structure. • Sm, Dy and Ho dopants improved the electrochemical and optical properties of MF. • The magnetic properties of MF were improved. • The produced photocatalysts were visible light active. [ABSTRACT FROM AUTHOR]

Magnetoelectric nanoparticles (NPs) present an important class of nanomaterials with a wide interest in piezocatalytic and biomedical applications. Herein, the results of magnetoelectric and magnetization measurements performed on core–shell NPs having magnetic core (MnFe2O4, MFO) and ferroelectric shell (Ba0.85Ca0.15Ti0.5Zr0.5O3, BCZT) synthesized by the microwave hydrothermal method are reported. Magnetic results are compared with the measurements on reference MFO NPs prepared under identical conditions. Detailed SQUID magnetometer measurements of the magnetization hysteresis loops M(H) down to 2 K reveal the existence of a clear exchange bias effect in pure MFO NPs attributed to the coexistence of ferromagnetic and antiferromagnetic short‐range interactions. When the magnetic core is covered by the thin ferroelectric BCZT shell, it is observed that 1) the shell suppresses the apparent bias effect and 2) induces an “extra” ferromagnetic magnetization at T < 20 K. The results indicate that this “extra” ferromagnetism has a 2D character and it is most likely related to the interface interactions between the MFO core and BCZT shell. Ferroelectric properties and strong magnetoelectric effect in core–shell NPs are revealed via piezoresponse force microscopy under magnetic field. The mechanisms of the observed effects are discussed. [ABSTRACT FROM AUTHOR]

This study used the sol-gel auto-combustion approach to successfully synthesise manganese ferrite (MnFe2O4) and cobalt-manganese ferrite (CoMnFe2O4) nanoparticles. Energy dispersive X-ray (EDX) analysis verifies the sample's chemical stoichiometry. The X-ray diffraction (XRD) method was used to verify the structure of the prepared ferrite. The particle size range determined by field emission scanning electron microscopy (FE-SEM) falls within the 42 to 99 nano meter range. The magnetic characteristics of nanostructures were assessed utilising vibrating-sample magnetometry (VSM). [ABSTRACT FROM AUTHOR]

The development of ozone-decomposition catalysts with high efficiency and exceptional resistance to humidity is a significant challenge, as ozone is a primary air pollutant. This study successfully synthesized a series of MnxFe3–xO4 catalysts with varying crystal structures by adjusting the Mn/Fe molar ratios through a coprecipitation method with inorganic salt precursors. Compared to crystalline Mn3O4 and Fe2O3, the obtained amorphous MnFe2O4(MnFe-1) nanocatalyst exhibited an optimal ozone conversion rate of 99.9% for 50 ppm O3 with a space velocity (SV) of 600 L g–1 h–1 in dry gas and 77.4% for 50 ppm O3 with a SV of 600 L g–1 h–1 under a relative humidity (RH) of 60%. The superior performance of the amorphous sample can be attributed not only to its smaller size and larger surface area but also to the presence of Mn3+ as the active site, a higher number of oxygen vacancies and acid sites, and the synergistic effect between iron and manganese. This research offers a universally applicable preparation method for nanosized spinel oxides and provides an in-depth exploration of the ozone-decomposition mechanism. [ABSTRACT FROM AUTHOR]

Background: Superparamagnetic properties and excitation independence have been incorporated into carbon-decorated manganese ferrite nanodots (MnFe@C) to introduce an economical and safer multimodal agent for use in both T1-T2 MRI and fluorescence-based imaging to replace the conventional highly toxic heavy metal contrast agents. Methods: The surface conjugation of 8-anilino-1-naphthalenesulfonate (ANS) to MnFe@C nanodots (ANS-MnFe@C) enhances both longitudinal and transverse MRI relaxation, improves fluorescence for optical imaging, and increases protein detection sensitivity, showing higher multimodal efficacy in terms of molar relaxivity, radiant efficiencies, and fluorescence sensitivity compared to MnFe@C. Results: The band gap energy was determined using Tauc’s equation to be 3.32 eV, while a 72% quantum yield demonstrated that ANS-MnFe@C was highly fluorescent, with the linear range and association constant calculated using the Stern–Volmer relation. The synthesized ANS-MnFe@C demonstrated excellent selectivity and sensitivity for bovine serum albumin (BSA), with a nanomolar detection limit of 367.09 nM and a broad linear range from 0.015 to 0.225 mM. Conclusions: In conclusion, ANS-MnFe@C holds ease of fabrication, good biocompatibility, as assessed in A375 cells, and an effective pH-sensitive doxorubicin release profile to establish anticancer activity in lung cancer cell line (A549), highlighting its potential as an affordable therapeutic agent for multimodal imaging, drug delivery, and protein sensing.

Herein, thermodynamic assessment is proposed to screen suitable precursors for the solid-state synthesis of manganese ferrite, by mechanosynthesis at room temperature or by subsequent calcination at relatively low temperatures, and the main findings are validated by experimental results for the representative precursor mixtures MnO + FeO3, MnO2 + Fe2O3, and MnO2 +2FeCO3. Thermodynamic guidelines are provided for the synthesis of manganese ferrite from (i) oxide and/or metallic precursors; (ii) carbonate + carbonate or carbonate + oxide powder mixtures; (iii) other precursors. It is also shown that synthesis from metallic precursors (Mn + 2Fe) requires a controlled oxygen supply in limited redox conditions, which is hardly achieved by reducing gases H2/H2O or CO/CO2. Oxide mixtures with an overall oxygen balance, such as MnO + Fe2O3, act as self-redox buffers and offer prospects for mechanosynthesis for a sufficient time (>9 h) at room temperature. On the contrary, the fully oxidised oxide mixture MnO2 + Fe2O3 requires partial reduction, which prevents synthesis at room temperature and requires subsequent calcination at temperatures above 1100 °C in air or in nominally inert atmospheres above 750 °C. Oxide + carbonate mixtures, such as MnO2 +2FeCO3, also yield suitable oxygen balance by the decomposition of the carbonate precursor and offer prospects for mechanosynthesis at room temperature, and residual fractions of reactants could be converted by firing at relatively low temperatures (≥650 °C). [ABSTRACT FROM AUTHOR]

A low-cost and high-efficiency solid reaction method has been reported as an effective technology to synthesize manganese ferrite MnFe2O4 with a spinel crystal structure. This work clarified the underlying reason for the influence mechanism of SiO2 and Al2O3 on the synthesis of MnFe2O4. Synthetic MnFe2O4 polyhedral microparticles with a saturated magnetization of 71.19 emu/g, a ratio of saturation magnetization to residual magnetization (Ms/Mr) of 0.062 and a coercivity (Hc) of 6.50 Oe were successfully obtained at an oxidization roasting temperature of 1100 °C for 60 min. The experimental results indicate that the tetrahedral Mn2+ ions and octahedral Mn3+ ions in the crystal structure of manganese ferrite MnFe2O4 were replaced by tetrahedral Si2+ ions and octahedral Al3+ ions from (Mn2+)x(Fe2+)y(Si2+)1−x−y[Fe3+]2O4 and (Mn2+)[Fe3+]2−x[Al3+]xO4, respectively. In addition, hercynite FexMn1−xAl2O4 with a spinel crystal structure and olivine MnxFe2−xSiO4 with an orthorhombic crystal structure were partially formed in the synthesis of manganese ferrite MnFe2O4, in which some Fe2+ ions were easily replaced by Mn2+ ions to form stable hercynite MnAl2O4 and olivine Mn2SiO4 in these crystal structures. The current research work provides comprehensive insights for synthesizing manganese ferrite MnFe2O4 and continuously advances its technical progress. [ABSTRACT FROM AUTHOR]

The novel co-precipitation technique has been employed to create the manganese ferrite nanoparticle. The prepared sample was annealed for various temperatures 400 °C, 600 °C and 700 °C. Based on TG/DT analysis the optimal temperature was found to be 700 °C and further additional analysis was performed for the sample annealed at 700 °C. Their morphology and properties were determined using SEM, HR-TEM, EDX, FTIR, XPS, BET, and CV techniques. Using the X-ray diffraction technique, the prepared sample's structural characteristics were demonstrated. The SEM as well as HR-TEM images showed the nanoparticles had a roughly spherical shape. The EDX analysis confirmed the presence of the elements Fe, O, and Mn in the sample; there was no evidence of contamination by other elements. The specific surface area of the nanoparticles was estimated by BET analysis, which provides details of the material's porosity and surface area. The binding energy of the sample was estimated using XPS measurements, which provide details on the composition and chemical states of the individual elements. By using cyclic voltammetry, the nanoparticles' electrochemical characteristics were evaluated. For a reduced scan rate of 2 mVs−1, the specific capacitance value was discovered to be 341 Fg-1, confirming their suitability for super capacitor applications.

In this study, we investigated the benefit of combining Chlorella sorokiniana with manganese-containing ferrite nanoparticles (NPs) for heavy metal removal and cell harvesting. Our results demonstrate that the combination of non-toxic nanoparticles significantly enhances the heavy metal removal capacity of C. sorokiniana without affecting its growth. The microalgae combined with NPs was able to sequester Cr6+, Co2+, and Ni2+ from aqueous solutions and could remove these metals at a higher adsorption capacity and within a relatively short time than their individual counterparts, indicating a synergistic effect between the algal cells and the nanomaterials, where bioadsorption and chemisorption were the main players. Both biosorption and chemisorption capacities were found to be the highest for single-metal systems and decreased when coexisting ions were present in the solution. The adsorption of the heavy metals evaluated was better described by the pseudo-second order model than the pseudo-first order model, indicating that chemisorption dominated over physisorption. These characteristics suggest that the combination of biosorbents with nanosorbents is a promising approach for the treatment of water contaminated with heavy metals making this process more efficient, economical, sustainable, and clean.

Due to the coupled transformations between metal ions with variable valence states, manganese ferrite (MnFe2O4) is regarded as an efficient catalyst in a heterogeneous Fenton-like system for the degradation of organic contaminants. In this work, the magnetic nanoscale MnFe2O4 was synthesized via a simple hydrothermal method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM). Results on the degradation tests indicated a high catalytic ability of MnFe2O4 nanocrystals to activate hydrogen dioxide (H2O2) to degrade active dye rhodamine B (RhB). Moreover, the RhB degradation process in the MnFe2O4-H2O2 Fenton-like system followed a Behnajady–Modirshahla–Ghanbery (BMG) kinetic model. The catalytic conditions, including catalyst dosage, RhB concentration, H2O2 dosage, solution pH and reaction temperature, had essential effects on RhB degradation efficiency and BMG kinetic parameters. The process optimization of RhB degradation was designed by central composite design (CCD) under response surface methodology (RSM). A mathematic model of the quadratic polynomial was established for the fitting analysis of RhB degradation, which was significant and reliable by the analysis of variance (ANOVA). Based on the programmed prediction, the optimum parameters for RhB degradation in the MnFe2O4–H2O2 system were determined as 2 of solution pH, 19.6 mmol·L−1 of H2O2 dosage, 2.0 g·L−1 of catalyst dosage and 180 min of reaction time. Under these optimum conditions, the predicted and experimental values of RhB degradation efficiency were 99.42% and 98.17%, respectively. [ABSTRACT FROM AUTHOR]

Currently, researchers are struggling with the development of energy storage systems, like high energy density supercapacitors, with cheap cost and high stability. Herein research we present a facile preparation and evaluation of the manganese ferrite/graphene oxide (MnFe 2 O 4 /GO) nanocomposite electrochemical behavior as active electrode material in supercapacitors. The chemical composition and morphology were specified with different physicochemical characterization techniques. The TEM and FESEM images exhibit MnFe 2 O 4 semi-spherical nanoparticles on GO plates. The prepared electrodes performance were proceeded with charge-discharge galvanostatic measurement (GCD), electrochemical impedance (EIS), and cyclic voltammetry (CV). The specific capacity value of MnFe 2 O 4 /GO new composite determined 298 F g−1 in 1 A/g current density. Also MnFe 2 O 4 /GO electrodic composite shows acceptable GCD stability, by maintaining its original capacity of 92% at 500 cycles. The EIS analysis also displays low internal resistance of MnFe 2 O 4 /GO compared to other electrodes in the same conditions. In addition to experimental analysis, density functional theory was also used to get a more accurate understanding of the electrochemical behavior of electrode materials. The theoretical results showed that with the formation of MnFe 2 O 4 /GO nanocomposite, the electron conductivity is improved (energy gap decreases to 0.019 eV) and leads to an increase in supercapacitor performance, which is in agreement with the experimental results. • MnFe 2 O 4 /GO nanocomposite shows acceptable stability (92% at 500 cycles). • The MnFe 2 O 4 /GO showed improved performance as supercapacitor electrode. • The attraction of charge density from MnFe 2 O 4 to GO enhance the charge storage. • Density functional theory calculation results were in good with experimental results. [ABSTRACT FROM AUTHOR]

Functional magnetic loofah (FMC) was prepared by a chemical graft of magnetic nanoparticles MnFe2O4 onto the loofah (ML) after being pretreated and carbonized by NaOH, and its adsorption properties as adsorbent for uranium-containing wastewater were studied. The results show that the equilibrium adsorption capacity of FMC for uranyl ions is 270.95 mg/g. The adsorption process is spontaneous and exothermic. Langmuir's isothermal model and the quasi-second order model are both suitable for describing the process of adsorption. The adsorption mechanism shows that the rich oxygen-containing functional groups and amino groups on the surface of FMC bind to U(VI) through complexation, and the MnFe2O4 in FMC reacts with U(VI) to remove U(VI) from the aqueous solution. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

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In this work, the MnFe2O4/BGA (boron-doped graphene aerogel) composite prepared via the solvothermal method is applied as a photocatalyst to the degradation of tetracycline in the presence of peroxymonosulfate. The composite's phase composition, morphology, valence state of elements, defect and pore structure were analyzed by XRD, SEM/TEM, XPS, Raman scattering and N2 adsorption–desorption isotherms, respectively. Under the radiation of visible light, the experimental parameters, including the ratio of BGA to MnFe2O4, the dosages of MnFe2O4/BGA and PMS, and the initial pH and tetracycline concentration were optimized in line with the degradation of tetracycline. Under the optimized conditions, the degradation rate of tetracycline reached 92.15% within 60 min, whereas the degradation rate constant on MnFe2O4/BGA remained 4.1 × 10−2 min−1, which was 1.93 and 1.56 times of those on BGA and MnFe2O4, respectively. The largely enhanced photocatalytic activity of the MnFe2O4/BGA composite over MnFe2O4 and BGA could be ascribed to the formation of type I heterojunction on the interfaces of BGA and MnFe2O4, which leads to the efficient transfer and separation of photogenerated charge carriers. Transient photocurrent response and electrochemical impedance spectroscopy tests offered solid support to this assumption. In line with the active species trapping experiments, SO4•− and O2•− radicals are confirmed to play crucial roles in the rapid and efficient degradation of tetracycline, and accordingly, a photodegradation mechanism for the degradation of tetracycline on MnFe2O4/BGA is proposed. [ABSTRACT FROM AUTHOR]

The manganese ferrite has been processed by mechanosynthesis, using reactive siderite and MnO 2 powder mixtures, with and without subsequent heat treatment. Taguchi planning was used to assess the impact of milling conditions (rotational speed and time) and subsequent calcination temperature on conversion of precursors, based on integrated intensities of the main XRD peaks of precursor phases FeCO 3 (104) and MnO 2 (110), and spinel phase (311), using Ni as internal pattern. Thermogravimetry provided additional information on the residual contents of reactants in the as-milled samples. The best conditions for complete conversion to spinel phase of as-milled samples were obtained by milling at 650 rpm, for 6 h ( I 311 , s p / I 111 , N i = 2.41) , and for calcined samples were obtained after milling at 650 rpm, for 3 h, and calcination at 650 °C (I 311 , s p / I 111 , N i = 2.35). The impact of processing conditions on structural features of the spinel phase was accounted by the contributions to variance of intensity of its (311) reflection, which were 90% ascribed to rotational speed and only 4% ascribed to milling time, for as-milled samples, or 58%, 15% and 16% ascribed to rotational speed, milling time and calcination temperature, for calcined samples. Readier conversion of FeCO 3 relative to MnO 2 occurred during the milling stage, at low or intermediate rotational speed, with impact on M n : F e ratio in the spinel phase, as revealed by changes in lattice parameter of as-milled samples, in the range of 0.8424–0.8464 nm. Subsequent calcination minimized or eliminated traces of secondary phases. The incorporation of magnesium oxide and possibly other secondary components of the siderite precursor also induced structural changes in the resulting spinel phase, mainly in calcined samples (a o = 0.8370–0.8434 nm). Partial oxidation also contributed to structural changes in calcined samples, as revealed by differences between samples calcined in inert and oxidising atmospheres. [ABSTRACT FROM AUTHOR]

In this work, stabilized ionotropic hydrogels were designed using sodium carboxymethyl cellulose (CMC) and assessed as inexpensive sorbents for hazardous chemicals (e.g., Methylene Blue, MB) from contaminated wastewaters. In order to increase the adsorption capacity of the hydrogelated matrix and facilitate its magnetic separation from aqueous solutions, sodium dodecyl sulfate (SDS) and manganese ferrite (MnFe2O4) were introduced into the polymer framework. The morphological, structural, elemental, and magnetic properties of the adsorbents (in the form of beads) were assessed using scanning electron microscopy (SEM), energy-dispersive X-ray analysis, Fourier-transform infrared spectroscopy (FTIR), and a vibrating-sample magnetometer (VSM). The magnetic beads with the best adsorption performance were subjected to kinetic and isotherm studies. The PFO model best describes the adsorption kinetics. A homogeneous monolayer adsorption system was predicted by the Langmuir isotherm model, registering a maximum adsorption capacity of 234 mg/g at 300 K. The calculated thermodynamic parameter values indicated that the investigated adsorption processes were both spontaneous (ΔG < 0) and exothermic (ΔH < 0). The used sorbent can be recovered after immersion in acetone (93% desorption efficiency) and re-used for MB adsorption. In addition, the molecular docking simulations disclosed aspects of the mechanism of intermolecular interaction between CMC and MB by detailing the contributions of the van der Waals (physical) and Coulomb (electrostatic) forces. [ABSTRACT FROM AUTHOR]

This paper describes the structural and magnetic properties of MnFe 2 O 4 , which is currently widely used and is considered to be one of the promising materials. Although these features of our subject of study have been considered before us, we wanted to confirm the accuracy of these characteristics for our future purposes. In the study of the structural feature, the analysis of Raman spectroscopy was considered and the high purity of nanosized particles was revealed. The magnetic properties were analyzed by electron paramagnetic resonance (EPR) and the presence of unpaired electrons was detected, and the linewidth between the peaks (Δ H PP = 1 2 8 7 G) and the g -factor (2282) was measured. [ABSTRACT FROM AUTHOR]

In this research, manganese ferrite (MnFe2O4) thin film and spherical nanoparticles were synthesized using the e-beam evaporation type of PVD and sol-gel method, respectively. Also, the effect of morphology on the structural, linear, and nonlinear optical properties of samples was investigated. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to assess the surface morphology of the specimens. The nonlinear optical (NLO) properties were also explored by the Z-scan technique utilizing CW laser at 532 nm. Different incident powers of laser were evaluated during nonlinearity assessments. In this research, MnFe2O4 nanoparticles showed higher nonlinear responses than MnFe2O4 thin film. The nonlinear refractive (NLR) indices and nonlinear absorption (NLA) coefficient of MnFe2O4 nanoparticles were 10−4 cm2/W and 10 W/cm, respectively. The obtained optical nonlinearity can be assigned to the two-photon absorption and the self-focusing effect. In addition, thermal nonlinearity explains the changes in the value of β and n2 for MnFe2O4 nanoparticles and thin films. The higher nonlinearity in the nanoparticle sample than thin film can be due to nanoparticle clusters in solution of MnFe2O4. The good nonlinear optical properties of MnFe2O4 indicate that this material can be the promising potential in nonlinear photonic devices. [ABSTRACT FROM AUTHOR]

Mixed magnetic composites of manganese ferrite and cristobalite (MnFe 2 O 4 –SiO 2) were produced by the solid-state reaction method, using as starting materials in natura ores found in the state of Rio Grande do Norte – Brazil. Based on the stoichiometric proportions of the precursor ores, various composites in the form of powders and pellets were synthesized at a temperature of 1200 °C/12h under ambient atmosphere. Samples in the form of pellets were made at compression pressures of 370 and 740 MPa to investigate the effect of pressure on the physicochemical, and dielectric properties of the material. Structural, morphological and magnetic analyses were studied for the series of samples. X-ray diffractogram (XRD) results confirmed the formation of the mixed spinel phase MnFe 2 O 4 with cubic symmetry and space group Fd-3m:1, together with peaks corresponding to SiO 2 –cristobalite. The Rietveld refinements identified a predominance of about 90% of the MnFe 2 O 4 phase with crystallite variations of 130–190 nm due to the effect of compaction pressure. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electronic microscopy (TEM) mappings show clusters of triangular crystals in the pellets series. Magnetic hysteresis cycles at room temperature show a fast magnetization saturation (M S) response in a field of ∼4 kOe, with parameters dependent on the size and shape of the crystallites. The magnetically soft ferrites exhibited very low coercive field values. The hysteretic curves measured at 5 K showed a significant gain in the M S of ∼30 emu/g. Analyzes of magnetization as a function of temperature identified a blocked regime with a maximum ∼97 K (powder) and ∼170 K (pellets), and an irreversibility of the ZFC–FC curves up to room temperature. An indication of a spin-glass (SG) like state close to 20 K can also be seen in these results. Dielectric characterization of the pellets was performed from 1.0 to 8.5 GHz, and presented well-defined behavior, where real permittivity can be highly related to Rietveld refinement of XRD, and SEM/EDS results. This research suggests the feasibility of producing manganese ferrite composites directly from minerals, without the use of high-purity chemical reagents, allowing their obtainment on a large scale for commercial use. [ABSTRACT FROM AUTHOR]

The transformations of low-grade manganese ore were investigated during roasting in the air at different temperatures up to 1200°C. The transformations were followed up by XRD and TGA-DTA. Moreover, the morphology and magnetic properties were determined by SEM and VSM. It was observed that MnO2 transformed to the lower oxide Mn5O8 at 500°C and then to bixbyite (Mn2O3) at 600°C. Finally, the bixbyite decomposed to hausmannite (Mn3O4) at 800°C. Increasing the roasting temperature to 900°C induced a reaction between hematite and hausmannite and led to the formation of a small amount of solid solution of the ferrite spinel MnFe2O4. Further increase in temperature to 1000°C led to the formation of a solid solution of braunite (Mn7SiO12) which decomposed to rhodonite (MnSiO3) at 1200°C. The magnetic susceptibility of the original ore gradually increased with the roasting temperature, from 0.119 × 10−3 at ambient temperature to a maximum value of 80 × 10−3 at 1200°C. [ABSTRACT FROM AUTHOR]

The work emplaced in this research is the synthesis of cobalt ferrite nanoparticles (CFNPs) doped with manganese and magnesium for antibacterial activities by sol-gel protocol. The physicochemical properties of CFNPs, Mg_CFNPs and Mn_CFNPs as described by the characterization techniques shows good results. Cubic spinel structures of CFNPs, Mg_CFNPs and Mn_CFNPs were observed by the X-ray diffraction (XRD) technique. The transmission electron microscope (TEM) established the spherical shape of the samples. The functional groups embedded in the sample were observed using FTIR and complimented by the Raman analysis. The formulated sample was used against four pathogenic strains S. epidermidis; B. subtilis; E. coli and K. pneumoniae. Higher susceptibility against E. coli was observed with Mg_CFNPs compared to the pristine (CFNPs) and Mn_CFNPs. Hence, the formulated Mg_CFNPs are highly significant and propitious for antibacterial activities.

Highlights Satisfactory p-ASA degradation was achieved in a wide pH range. Simultaneous removal of p-ASA and the released arsenic was achieved in biochar supported MnFe2O4/persulfate system. Generation abundant reactive oxygen species via redox cycles between Mn and Fe.

In this research, we introduced the manganese ferrite/tungsten disulfide as novel catalyst by modification of MnFe2O4 with WS2 for the first time. The desired catalyst identified by different techniques and was used in the photocatalytic reduction reaction of a wide range of nitroaromatic compounds using N2H4.H2O at 25 °C. The results of the catalytic photoreduction reaction of nitrobenzene, 1,2-dinitrobenzene and 1,4-dinitrobenzene were superb and showed 100% efficiency within 10 min. This novel photocatalyst represented high magnetic recycling and reusability performance for the reduction reactions even after 20 times of reuse.

Simple Summary: Magnetic ferrite nanocomposite has drawn huge interest in nanomedicine in areas related to thermotherapy, cell labeling-tracking and magnetic resonance imaging. Manganese ferrite spinel is an interesting magnetic nanocomposite due to its superparamagnetic nature, strong T2 MRI contrast, low synthesis cost, and eco-friendliness. The present study investigated the suitability of two different nanocarriers: one with a silica base (MnFe2O4/silica), and another with a carbon base (MnFe2O4/Graphene oxide) for targeted cancer therapy. The phase, textural and morphological variation of the two different nanoformulations was examined using various physico-chemical techniques. Pegylated and as-such nanoformulations were studied in drug delivery and in vitro using cancerous and non-cancerous cell lines. Density functional theory was used to calculate the binding energies between cisplatin on single-silica or multi-layered graphene oxide. Immunofluorescence images were captured using c-caspase 3/7 and TEM analysis. MnFe2O4/silica/cisplatin nanocomposites was found be a better chemotherapeutic drug delivery option than MnFe2O4/GO/cisplatin nanocomposites. In nanotherapeutics, gaining insight about the drug interaction with the pore architecture and surface functional groups of nanocarriers is crucial to aid in the development of targeted drug delivery. Manganese ferrite impregnated graphene oxide (MnFe2O4/GO) with a two-dimensional sheet and spherical silica with a three-dimensional interconnected porous structure (MnFe2O4/silica) were evaluated for cisplatin release and cytotoxic effects. Characterization studies revealed the presence of Mn2+ species with a variable spinel cubic phase and superparamagnetic effect. We used first principles calculations to study the physisorption of cisplatin on monodispersed silica and on single- and multi-layered GO. The binding energy of cisplatin on silica and single-layer GO was ~1.5 eV, while it was about double that value for the multilayer GO structure. Moreover, we treated MCF-7 (breast cancer cells) and HFF-1 (human foreskin fibroblast) with our nanocomposites and used the cell viability assay MTT. Both nanocomposites significantly reduced the cell viability. Pt4+ species of cisplatin on the spinel ferrite/silica nanocomposite had a better effect on the cytotoxic capability when compared to GO. The EC50 for MnFe2O4/silica/cisplatin and MnFe2O4/GO/cisplatin on MCF-7 was: 48.43 µg/mL and 85.36 µg/mL, respectively. The EC50 for the same conditions on HFF was: 102.92 µg/mL and 102.21 µg/mL, respectively. In addition, immunofluorescence images using c-caspase 3/7, and TEM analysis indicated that treating cells with these nanocomposites resulted in apoptosis as the major mechanism of cell death. [ABSTRACT FROM AUTHOR]

Carbon-decorated ferrite nanodots (MNF@Cs) have been enhanced with superparamagnetism and higher fluorescence quantum yield by encapsulation with an alginate derivative to create a cost-effective and less toxic multimodal contrast agent for replacing the conventional heavy metal Gd-containing contrast agent used in MR imaging. The novel surface-engineered particles (MNF@C-OSAs), devoid of labels, can simultaneously provide both longitudinal and transverse relaxation-based magnetic resonance imaging (MRI) and fluorescence emission. According to the findings of in vitro studies, the calculated molar relaxivities and the molar radiant efficiencies are indicative of the multimodal efficacy of MNF@C-OSA as compared with MNF@C particles and conventional contrast agents used in medical imaging. MNF@C-OSAs were shown to be significantly biocompatible and negligibly toxic when assessed against A549 cells and zebrafish embryos, indicating their potential for use as theranostic agents. [ABSTRACT FROM AUTHOR]

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The development of nanocomposites for environmental demands is a challenge due to numerous precautions, including tailoring recyclable agents. In this work, bentonite clay (B. Clay)/manganese ferrite (MnFe2O4) nanocomposites have been fabricated via a solid-state technique that is green, efficient, and scalable. The obtained composites have been characterized using FTIR, SEM, and TEM. From the results, MnFe2O4 was configured in spherical shape during the interaction with B. Clay, reflecting the quality of applications. The studied average maximum height of the roughness (Rtm) changes from 151.7 to 107.3 and increases to 141.5 for pure B. Clay, MnFe2O4, and the nanocomposite, respectively. The surface area for the nanocomposite was around 85.45 m2/g compared with 57. 46 m2/g for MnFe2O4. The magnetic domain has been enhanced exponentially to be 19.93 emu/g after solid synthesis of MnFe2O4 with B. Clay. The adsorption property was more significant in the case of MnFe2O4/B. clay to reach 71.6% decolorization of methylene blue (MB). Otherwise, under light illumination, the phytoremediation Fe3+ is reduced to Fe2+, accelerating switching on/off Fe3+/Fe2+ cycle stability to exhibit strong hydroxyl radicals able to destroy MB within 8 min. Also, at 100 μg/ml concentration, the prepared MnFe2O4/B. Clay was aggressive against Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli.

Abstract Background The study of symbiotic nitrogen fixation between (SNF) legumes and rhizobia has always been a hot frontier in scientific research. Nanotechnology provides a new strategy for biological nitrogen fixation research. However, how to construct abiotic nano-structure-biological system, using the special properties of nanomaterials, to realize the self-enhancement of biological nitrogen fixation capacity is important. Results In order to construct a more efficient SNF system, in this study, we applied manganese ferrite nanoparticles (MF-NPs) with sustainable diatomic catalysis to produce reactive oxygen species (ROS), thus regulating the nodulation pathway and increasing the number of nodules in soybean (Glycine max), eventually enhancing symbiotic nitrogen fixation. Symbiosis cultivation of MF-NPs and soybean plants resulted in 50.85% and 61.4% increase in nodule weight and number, respectively, thus inducing a 151.36% nitrogen fixation efficiency increase, finally leading to a 25.70% biomass accumulation increase despite no substantial effect on the nitrogenase activity per unit. Transcriptome sequencing analysis showed that of 36 differentially expressed genes (DEGs), 31 DEGs related to soybean nodulation were upregulated in late rhizobium inoculation stage (12 d), indicating that the increase of nodules was derived from nodule-related genes (Nod-R) continuous inductions by MF-NPs. Conclusions Our results indicated that the nodule number could be effectively increased by extending the nodulation period without threatening the vegetative growth of plants or triggering the autoregulation of nodulation (AON) pathway. This study provides an effective strategy for induction of super-conventional nodulation. Graphical Abstract

[Display omitted] • Investigating reduce graphene oxide/manganese ferrite nanocomposite: synthesis, characterization and carbon monoxide oxidation. • Effect of pretreatment on the (%) CO conversion by 1 wt% rGO/MnFe 2 O 4. • Effect of GHSV on CO conversion CO/O 2. • Characterization and catalytic performance of rGO-enhanced MnFe 2 O 4 nanocomposites in CO oxidation. • Investigating mechanism of CO oxidation. In this work, different weight ratio of reduce graphene oxide (rGO) incorporated manganese ferrite (MnFe 2 O 4) is successfully prepared using reduction photolysis method. To have good spacing of layer, expanded graphite was employed for synthesis of graphene oxide by Hummer modified method. The synthesized rGO/MnFe 2 O 4 nanocomposite was characterized by FTIR, EDX, Raman, XRD, BET, XPS, TGA, TPR and FESEM, while the magnetic properties are investigated employing VSM technique. The catalytic results demonstrated that the MnO 2 and Fe 2 O 3 have low catalytic activity and it is not active at temperature lower than 130 °C. The highest efficiency was noted for the MnFe 2 O 4 nanocomposite. The demonstrated results appeared that the doped of rGO inter MnFe 2 O 4 considerably improved the efficiency for oxidation of CO. On the other hand, the highest conversion was obtained for the 1 wt% rGO doped MnFe 2 O 4 and it displayed a CO conversion of 100 % at 80 °C. 1 wt% rGO/MnFe 2 O 4 with conversion 98% CO demonstrated higher activity compared with Fe 2 O 3 and MnFe 2 O 4. On the other hand, the results exhibited that the 1 wt% rGO/MnFe 2 O 4 pretreated under oxidizing conditions appeared higher activity compared with synthesized catalyst dealt under reductive conditions, which assign to the higher adsorption capacity of O 2 , as well as, the results also appeared that the catalyst showed high stability under wet and dry conditions. [ABSTRACT FROM AUTHOR]

• MFO dispersed on AC were prepared by simple gel combustion from low-cost precursors. • Paramagnetic MFC can be recovered from solution by applying an external magnet. • AC supports limited particle agglomeration and enhanced photocatalytic activity of MFO. • MFC (E g = 2.02 eV) efficiently removed ≥90 % of PCP within 2.5 h under mild conditions. • Study on active species and degradation mechanism showed crucial roles of e¯ and •OH. Magnetically recoverable spinel manganese ferrite (MFO) nanoparticles (NPs) supported on activated carbon (AC) (MFC), a promising photocatalyst, were prepared by simple and cost-effective gel combustion. AC supports prevented particle agglomeration and functioned as electron acceptors to promote charge separation on MFO. MFC samples demonstrated significant surface area, paramagnetic characteristics, and visible-light absorption bandgap of 2.02 eV. Pentachlorophenol (PCP) photodegradation using MFC showed degradation efficiency of at least 90 % after 150 min at pH 6.0 with the catalyst dose and PCP concentration of no more than 10 mg. L −1 and 9.0 ppm, respectively. MFC exhibited durability and recyclability with approximately 4 % decrease in degradation efficiency after five reuses while maintaining its material structure. The crucial roles of photo-generated electrons and hydroxyl radicals related to dechlorination and hydroxylation during PCP photodegradation were also highlighted in active species investigations with appropriate scavengers. Subsequently, a plausible PCP photodegradation mechanism with intermediates was proposed. The MnFe 2 O 4 nanoparticles with cubic spinel structure dispersed on activated carbon were prepared by the gel-combustion method from low-cost precursors and used as a magnetically recoverable photocatalyst for the degradation of persistent organic pollutants in wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • MnFe 2 O 4 /Biochar (MFB) synergistically enhances pollutant degradation in water. • Stable and recyclable MFB-1:2 degraded tetracycline (TC) despite interferents. • O 2 –•,·1O 2 , IO 3 •, and •OH promoted TC degradation in MFB-1:2/periodate system. • Ecotoxicity of degradation intermediates was assessed by T.E.S.T. • MFB-1:2/periodate is efficient for removing organic matter from freshwater. The periodate (PI)-based advanced oxidation process (AOP) is an economical and energy-saving method for remediating water by degrading pollutants. An efficient system for PI activation was developed by loading manganese ferrite spinel (MnFe 2 O 4) on biochar (BC) through a facile method, affording a metal-oxide MnFe 2 O 4 /BC composite catalyst. The developed system demonstrated significant effectiveness in eliminating various organic pollutants, particularly achieving high removal (5.26 and 2.83 times that of biochar and MnFe 2 O 4 , respectively) and mineralization (49.7 %) of the model pollutant tetracycline hydrochloride (TC) within 30 min. The system exhibited outstanding catalytic performance under various environmental conditions (pH, inorganic salts, humic acid, and real water bodies), as evidenced by quenching experiments and electron paramagnetic resonance (EPR) studies, proving that superoxide radicals (O 2 •-) are the main reactive species for TC degradation in the reaction system, in addition to singlet oxygen (1O 2), iodyl radicals (IO 3 •) and hydroxyl radicals (•OH). Potential pathways for TC degradation in this system were revealed based on density functional theory (DFT) and the ecological toxicity of the intermediates was analyzed through quantitative structure–activity relationship (QSAR) assessment. Analysis of the magnetic hysteresis and cycling stability demonstrated that the composites were stable and could be recycled by applying a magnetic field. This work opens a new pathway for designing efficient PI activators for the selective oxidation of organic pollutants and highlights the potential application of this system in practical wastewater treatment. [ABSTRACT FROM AUTHOR]

A low-cost and high-efficiency solid reaction method has been reported as an effective technology to synthesize manganese ferrite MnFe2O4 with a spinel crystal structure. This work clarified the underlying reason for the influence mechanism of SiO2 and Al2O3 on the synthesis of MnFe2O4. Synthetic MnFe2O4 polyhedral microparticles with a saturated magnetization of 71.19 emu/g, a ratio of saturation magnetization to residual magnetization (Ms/Mr) of 0.062 and a coercivity (Hc) of 6.50 Oe were successfully obtained at an oxidization roasting temperature of 1100 °C for 60 min. The experimental results indicate that the tetrahedral Mn2+ ions and octahedral Mn3+ ions in the crystal structure of manganese ferrite MnFe2O4 were replaced by tetrahedral Si2+ ions and octahedral Al3+ ions from (Mn2+)x(Fe2+)y(Si2+)1−x−y[Fe3+]2O4 and (Mn2+)[Fe3+]2−x[Al3+]xO4, respectively. In addition, hercynite FexMn1−xAl2O4 with a spinel crystal structure and olivine MnxFe2−xSiO4 with an orthorhombic crystal structure were partially formed in the synthesis of manganese ferrite MnFe2O4, in which some Fe2+ ions were easily replaced by Mn2+ ions to form stable hercynite MnAl2O4 and olivine Mn2SiO4 in these crystal structures. The current research work provides comprehensive insights for synthesizing manganese ferrite MnFe2O4 and continuously advances its technical progress.

Emerging pollutants (EPs) are unchecked pollutants with inherent negative potentials present in the environment. There are heightened concerns about the availability and fate of these pollutants in the ecosystem because they cannot be removed by conventional wastewater treatment methods. Adsorption, a facile and scalable technique, is a method which can be used for the removal of emerging contaminants. Ketoprofen and benzophenone were used as representative EPs to investigate their sorption from aqueous solutions. Manganese ferrite biochar (MnFe2O4@BC) prepared via co-precipitation route was used as adsorbent. The MnFe2O4/biochar magnetic nanocomposite was octagonally shaped with an average particle size of 42.64 nm. The specific surface area (SBET) analysis revealed that the nanocomposite was mesoporous with a surface area of 197.64 m2/g. The maximum adsorption capacity (Qo) of ketoprofen and benzophenone was 8.09 and 7.02 mg/g at 20 °C. Thermodynamic investigation revealed that the uptake of ketoprofen was spontaneous while adsorption studies revealed that Langmuir and Freundlich isotherm fitted the adsorption data of ketoprofen and benzophenone. The positive heat of reaction shows that the adsorption process was endothermic. Fourier transform infrared (FTIR) data suggests that the uptake of adsorbates was by physisorption. The used nanocomposite could easily be recovered with water and reused while recyclability studies indicate the magnetic nanocomposites adsorbent could be reused up to five consecutive cycles.

Algal biofuel is a promising green energy for the future, but harvesting algae remains a major challenge. To overcome this obstacle, magnetic separation using magnetic nanoparticles is proposed as a simple, highly efficient yet cost-effective method to collect microalgae. Magnetite (Fe3O4) nanoparticles are the typical materials of choice, but their performance varies depending on the pH of the water, furthermore, they can be toxic to algal cells. Hence, a more stable and non-toxic alternative replacement for Fe3O4 is needed. In this work, we explore the use of biocompatible manganese-containing magnetic ferrite nanoparticles (NPs) to harvest Chlorella sorokiniana and Scenedesmus obliquus microalgae. Using this novel NP, we achieved a harvesting efficiency of roughly 90% for Chlorella sorokiniana and 80% for Scenedesmus obliquus up to three cycles consistently throughout a wide pH range of 2–12. This was due to the high stability and reversible attachment of the NPs to the algal cells. Surface analysis of the NPs-Algae by Fourier transformed infrared (FTIR), the microbial adhesion to hydrocarbons (MATH), zeta potential, and the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory indicated acid-base interactions and hydrophobicity effects are the driven forces for NPs-algae interaction instead of simple electrostatic attraction. Overall, our study provided a more efficient magnetic harvesting approach for algae and a more in-depth understanding of the separation mechanisms to improve and advance the algae biofuel industry.

In this study, a composite of zinc oxide and manganese ferrite was synthesized using co-precipitation and hydrothermal routes, to be used as photocatalysts in reactions with UV/Vis light source. The synthesized materials were characterized by FTIR, XRD, and SEM, where it was possible to verify the efficiency of the syntheses performed, through the identification of the resulting phases, the evaluation of the structural morphology of the particles, and the analysis of the detachments of the main vibration bonds present in these materials. The composite ZnO/MnFe2O4 was used in photodegradation reactions of the antibiotic rifampicin, with catalyst dosage of 0.20; 0.40, and 0.60 g and 10 ppm of rifampicin, reactions using pure ZnO as a catalyst were also performed as a comparative parameter of the influence of MnFe2O4 in this system. The composite ZnO/MnFe2O4 showed a maximum percentage of rifampicin decontamination of 94.72% and ZnO, 74.20%using 0.20 g of photocatalyst after 90 min, which indicates a positive influence on this process. The solution treated with ZnO/MnFe2O4 was subjected to magnetic field induction for attraction and consequently accelerated removal of the solids present, successfully, compacting for the application of ZnO/MnFe2O4 to be presented as a promising material for decontamination of emerging pollutants through photocatalytic reactions. [ABSTRACT FROM AUTHOR]

In the present work, sulfur-doped manganese ferrites S@Mn(Fe2O4) nanoparticles were prepared by using the sol-gel and citrate method. The concentration of sulfur varied from 1 to 7% by adding Na2S. The samples were characterized by performing Fourier Transformed Infrared Spectroscopy (FTIR), Energy Dispersive X-ray (EDX), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Ultraviolet–Visible spectroscopy (UV–Visible). The synthesized sulfur-doped manganese ferrites were applied to evaluate the photocatalytic degradation of the dyes. Further, the degradation studies revealed that the nanoparticles successfully degraded the methylene blue dye by adding a 0.006 g dose under the sunlight. The sulfur-doped manganese ferrite nanoparticles containing 3% sulfur completely degraded the dye in 2 h and 15 min in aqueous medium. Thus, the ferrite nanoparticles were found to be promising photocatalyst materials and could be employed for the degradation of other dyes in the future. [ABSTRACT FROM AUTHOR]

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).

Hexavalent chromium (Cr(VI)) removal from aqueous solution with magnetic manganese ferrite has been demonstrated to be an effective method, however, its wide application is restricted as manganese ferrite was easy to aggregate by magnetism. Meanwhile, the effect of dissolved oxygen on the performance of magnetic manganese ferrite was still unclear. Hence, this study aimed to investigate the influence of ultrasound pretreatment and dissolved oxygen on Cr(VI) removal efficiency with manganese ferrite nanoparticles. The characterization results of pristine manganese ferrite indicated that the prepared nanoparticles were spherical with diameter around 200 nm, and the valence for manganese and iron element were +2 and +3, respectively. Subsequently, we compared the removal percentage of Cr(VI) in the presence or absence of dissolved oxygen with or without ultrasound pretreatment, and the results demonstrated that ultrasound pretreatment and the presence of dissolved oxygen increased the Cr(VI) removal percentage to 100%. Moreover, the high-resolution X-ray photoelectron spectroscopy (HR-XPS) results exhibited that the valence of Mn and Fe element did not changed during the Cr(VI) removal process, suggesting that Cr(VI) was separated from water via adsorption pathway. This deduction could be further verified by the HR-XPS spectra of Cr 2p after the reaction in the Ar and air condition. This research revealed the effect of ultra-sound pretreatment and dissolved oxygen on Cr(VI) removal with manganese ferrite and provided fundamental theory for the wide application of magnetic manganese ferrite for water treatment. [ABSTRACT FROM AUTHOR]

Aniline (AN) is one of the most important compounds in the chemical industry and is prepared by the catalytic hydrogenation of nitrobenzene (NB). The development of novel, multifunctional catalysts which are easily recoverable from the reaction mixture is, therefore, of paramount importance. Compared to conventional filtration, magnetic separation is favored because it is cheaper and more facile. For satisfying these requirements, we developed manganese ferrite (MnFe2O4)–supported, magnetically separable palladium catalysts with high catalytic activity in the hydrogenation of nitrobenzene to aniline. In addition to high NB conversion and AN yield, remarkable aniline selectivity (above 96 n/n%) was achieved. Surprisingly, the magnetic support alone also shows moderate catalytic activity even without noble metals, and thus, up to 94 n/n% nitrobenzene conversion, along with 47 n/n% aniline yield, are attainable. After adding palladium nanoparticles to the support, the combined catalytic activity of the two nanomaterials yielded a fast, efficient, and highly selective catalyst. During the test of the Pd/MnFe2O4 catalyst in NB hydrogenation, no by-products were detected, and consequently, above 96 n/n% aniline yield and 96 n/n% selectivity were achieved. The activity of the Pd/MnFe2O4 catalyst was not particularly sensitive to the hydrogenation temperature, and reuse tests indicate its applicability in at least four cycles without regeneration. The remarkable catalytic activity and other favorable properties can make our catalyst potentially applicable to both NB hydrogenation and other similar or slightly different reactions. [ABSTRACT FROM AUTHOR]

This study is focused on the kinetics and adsorption isotherms of amine-functionalized magnesium ferrite (MgFe2O4) for treating the heavy metals in wastewater. A sol-gel route was adopted to produce MgFe2O4 nanoparticles. The surfaces of the MgFe2O4 nanoparticles were functionalized using primary amine (ethanolamine). The surface morphology, phase formation, and functionality of the MgFe2O4 nano-adsorbents were studied using the SEM, UV-visible, FTIR, and TGA techniques. The characterized nanoparticles were tested on their ability to adsorb the Pb2+, Cu2+, and Zn2+ ions from the wastewater. The kinetic parameters and adsorption isotherms for the adsorption of the metal ions by the amine-functionalized MgFe2O4 were obtained using the pseudo-first-order, pseudo-second-order, Langmuir, and Freundlich models. The pseudo-second order and Langmuir models best described the adsorption kinetics and isotherms, implying strong chemisorption via the formation of coordinative bonds between the amine groups and metal ions. The Langmuir equation revealed the highest adsorption capacity of 0.7 mmol/g for the amine-functionalized MgFe2O4 nano-adsorbents. The adsorption capacity of the nanoadsorbent also changed with the calcination temperature. The MgFe2O4 sample, calcined at 500 °C, removed the most of the Pb2+ (73%), Cu2+ (59%), and Zn2+ (62%) ions from the water. [ABSTRACT FROM AUTHOR]