Fe3O4 Core Research Articles

Hydrogen adsorption and interactions in self-reducing shell hosted palladium nanoparticles on magnetite support

The nanoparticles (NP), consisting of hydrazine grafted organo-silica with PdNPs embedded shell on the Fe3O4 core, were prepared to study the adsorption and interactions of hydrogen in PdNPs and their support matrix. This material is expected to find the applications in the hydrogen technology including catalysis. The PdNPs were formed spontaneously in the organo-silica shell on magnetite nanoparticles by the reduction of Pd2+ ions with grafted hydrazine in the organo-silica shell. Thus formed NPs, termed as Fe3O4-GTEOS@PdNPs, were also thermally treated at 1033 K in Ar atmosphere to convert organic components to carbon. The chemical composition, physical structure, and magnetic properties were studied by high resolution transmission electron microscopy, X-rays diffraction, Mössbauer spectroscopy and X-ray photoelectron spectroscopy for the characterizations of physical, chemical and magnetic changes occurred in the Fe3O4-GTEOS@PdNPs after hydrogen adsorption-desorption at varying temperatures with respect to that in unused one. The hydrogen adsorption pressure-composition (PC) isotherms in Fe3O4-GTEOS@PdNPs followed the expected trend from 173 to 303 K as expected from PdNPs. However, thermally treated Fe3O4-GTEOS@PdNPs were found to adsorb lower amount of hydrogen due to oxidation of Pd0 to PdO and morphological changes during heating in Ar atmosphere. The comparison of nH/nPd value (0.49) obtained for the PdNPs in Fe3O4-GTEOS@PdNPs with the values those reported in the literature for different Pd materials showed the decrease in nH/nPd value with decrease in the size of Pd particles. This was attributed to stronger Pd–H bond in a nanoscale palladium, which prevented hydrogen transfer to interior matrix as compared to bigger Pd particles. The hydrogen adsorption PC isotherm at 373 K in Fe3O4-GTEOS@PdNPs could not be obtained as the unknown chemical reaction happened in the sample during the experiment. The considerably higher H2 consumption in the Fe3O4-GTEOS@PdNPs occurred at 373 K than that expected from the hydrogen adsorption in the PdNPs alone.

KBH4 Modification of Fe3O4 Core Shell Carbon Microspheres Promoted Persulfate Activation for Organic Contaminants degradation: Factors and Mechanism

KBH4 Modification of Fe3O4 Core Shell Carbon Microspheres Promoted Persulfate Activation for Organic Contaminants degradation: Factors and Mechanism

Surface physicochemical characteristics for sodium ion removal with sodium silicate modified magnetite core-shell nanoparticles and activation of their plasmid DNA purification ability

In this study, it is investigated the elimination of residual sodium ions from sodium silicate (Na2SiO3) modified Fe3O4@SiO2 nanoparticles, via the additional acidic treatment. Residual sodium ions are generated from the Na2SiO3 precursor during the titration for the fabrication of the Fe3O4@SiO2 core-shell structure; however, they were entirely removed after the in situ additional titration at pH 3 using a 1 M of hydrochloric acid (HCl). The thickness of the SiO2 shell layer of each nanoparticle was measured to 10 nm and the morphology of SiO2 shell on the Fe3O4 core were not significantly different after acid treatment to remove the residual sodium ions. However, the absolute zeta potential of the Na2SiO3-modified Fe3O4@SiO2 was decreased about 20% after HCl treatment (−52.5 ± 3.0 mV). In addition, the mean particle size of the Na2SiO3-modified Fe3O4@SiO2 was increased (363.98 nm) and the polydispersity index, which indicates dispersibility was increased (0.23) since residual sodium ions were eliminated by the acid treatment. It is assumed that the reducing anions in the diffuse layer of the particle due to the elimination of the residual sodium, as the counter ion, decreased the surface charge, thereby reducing the repulsive force between the Fe3O4@SiO2 nanoparticles. Then Fe3O4@SiO2 nanoparticles were utilized for separating plasmid DNA and separated plasmid DNA was measured with agarose gel electrophoresis and the absorbance monitoring. The efficiency of the DNA purification of the Na2SiO3-modified Fe3O4@SiO2 measured to 43.3 ± 5.2 ng/μl which was 58% increased after acid treatment. As a result, the dispersion/magnetic properties and DNA purification efficiency of the Na2SiO3-modified Fe3O4 became equivalent to the characteristics of the TEOS-modified Fe3O4@SiO2 using the additional acid treatment for sodium ions removal.

Accelerated and simplified synthesis of magnetic mesoporous nanoparticles in a continuous multistep microfluidic system

Here a fully continuous flow strategy for the preparation of Fe3O4@nSiO2@mSiO2 nanocomposites starting from ferrous and ferric ions was established for the first time. The three synthetic steps for Fe3O4 core, nonporous silica middle shell and mesoporous silica outer shell were connected and integrated into a single flow sequence with a total residence time of approximately 3 min. Moreover, the multistep continuous flow system was simplified with smaller footprint and increased safety by feeding all the ammonia needed by the three synthetic steps only once at the starting point of the system. The final product Fe3O4@nSiO2@mSiO2 nanoparticles with a specific surface area 378 m2 g−1 and saturation magnetization 19.3 emu g−1 showed great potential as a catalyst support with easy and excellent recyclability. Proved to be capable of achieving fast and accurate parameter optimization, the uninterrupted continuous flow system proposed in this work holds great prospects to mediate multistep synthesis of complex nanoparticles with hierarchical structures in an efficient and controllable manner.

PH and Magnetism Dual-Responsive Pickering Emulsion Stabilized by Dynamic Covalent Fe3O4 Nanoparticles.

Herein, we describe pH and magnetism dual-responsive liquid paraffin-in-water Pickering emulsion stabilized by dynamic covalent Fe3O4 (DC-Fe3O4) nanoparticles. On one hand, the Pickerinfigureg emulsions are sensitive to pH variations, and efficient demulsification can be achieved by regulating the pH between 10 and 2 within 30 min. The dynamic imine bond in DC-Fe3O4 can be reversibly formed and decomposed, resulting in a pH-controlled amphiphilicity. The Pickering emulsion can be reversibly switched between stable and unstable states by pH at least three times. On the other hand, the magnetic Fe3O4 core of DC-Fe3O4 allowed rapid separation of the oil droplets from Pickering emulsions under an external magnetic field within 40 s, which was a good extraction system for purifying the aqueous solution contaminated by rhodamine B. The dual responsiveness enables Pickering emulsions to have better control of their stability and to be applied more broadly.

Preparation and spectral studies of boronate ester modified magnetite iron nanoparticles (Fe3O4@APTES-B) as a new type of biological agents

We have designed two novel magnetite targeting biological agents (Fe3O4@APTES-B(1,2)) with a core of Fe3O4 and a shell made of boronate esters (APTES-B) to improve the biological effectiveness of magnetite Fe3O4 nanoparticles (MNPs). Initially, two boronate esters (B1) and (B2) have been prepared by 3,4-dihydroxybenzaldehyde and phenylboronic acid and/or butylboronic acid using a Dean-Stark apparatus to remove the water formed during the esterification reactions. Then, the APTES-B1,2 compounds have been synthesized via boronate esters and APTES in the presence of 1–2 drops of formic acid as catalyst. Finally, magnetite Fe3O4 NPs were added to APTES-B1,2 compounds to afford boronate ester modified magnetite iron nanoparticles (Fe3O4@APTES-B1,2) at ambient temperature, respectively. The boronate esters (B1) and (B2), APTES-B1,2 compounds, and boronate ester modified magnetite iron nanoparticles (Fe3O4@APTES-B1,2) were characterized using a combination of NMR (1H, 13C, and 11B), FT-IR, UV–Vis, LC-MS/MS, elemental analysis (CHN), XRD, SEM-EDX, EDX mapping, BET, and TG-DTA). Then, the antioxidant, antimicrobial and DNA binding activities of newly synthesized target compounds were tested. These results suggest that all compounds are also one of the propitious drug candidates and are worthy of further investigation.

Remarkable Magnetic Exchange Coupling via Constructing Bi‐Magnetic Interface for Broadband Lower‐Frequency Microwave Absorption

AbstractSevere lower‐frequency (2–8 GHz) microwave pollution caused by the rapid development of 5th generation (5G) communication posts significance on cutting‐edge microwave absorbers. However, the intensely coupled wave‐impedance and microwave dissipating ability dramatically hinder their performance in the exact lower‐frequency range. The rationally designed heterostructure of hard/soft ferrite composite provides an efficient solution to address the issue. In this context, core‐shell structured hard/soft BaFe(12‐x)CoxO19@Fe3O4 with abundant heterointerface is created using facile spray‐drying and subsequent solvothermal approach, where hard magnetic BaFe(12‐x)CoxO19 serves as the core and soft magnetic Fe3O4 serves as the shell, respectively. The unique core‐shell integration contributes sufficient magnetic exchange coupling interaction for strong magnetic loss beyond Snoek's limitation, which considerably boosts a lower‐frequency microwave absorption. Accordingly, the minimum reflection loss (RLmin) of typical BaFe11.6Co0.4O19@Fe3O4 microcomposite reaches −48.9 dB at the thickness of 3.5 mm, its bandwidth of reflection loss < −10 dB can cover almost all the S and C bands (2.6–8 GHz). Generally, an easy and controllable pathway is conveyed in this work to encourage improved magnetic loss ability as well as decouple the wave‐impedance and microwave dissipating ability in magnetic composites, which widens the road to the development of advanced lower‐frequency magnetic absorbers.

Highly Effective Lead Ion Adsorption by Manganese-Dioxide-Supported Core-Shell Structured Magnetite

In this research, a magnetic core-shell composite, consisting of a Fe3O4 core and a silica shell (called Fe3O4@SiO2), was developed and then functionalized via MnO2 grafting at different MnO2 deposition levels (termed Fe3O4@SiO2-MnO2). The resulting materials were characterized by X-ray fluorescence, X-ray diffraction, a vibration sample magnetometer, transmission electron microscopy, N2 adsorption-desorption, zeta-potential studies and X-ray photoelectron spectroscopy. Visualizations showed that Fe3O4@SiO2-MnO2 had a magnetite core with size of 100 nm, overlaid by a rough silica shell and a relatively loose MnO2 deposition. The Pb(II) adsorption onto the composites was also assessed. It was found that MnO2 deposition on the Fe3O4@SiO2 surface enhanced Pb(II) adsorption, and the Pb(II) adsorption amount was highly correlated to the MnO2 deposition level. The adsorption kinetics of Pb(II) followed pseudo-second-order kinetics, and the adsorption rate could be decreased by increasing the initial concentration of Pb(II). A higher pH resulted in enhanced Pb(II) adsorption, which slightly increased with the coexistence of Na+ and Ca2+, along with the presence of dissolved humic acid. The adsorbent could easily be separated and recovered under the action of the external magnetic component and it displayed stable adsorption behaviour over four adsorption-desorption periods. The results emphasize the high potential of Fe3O4@SiO2-MnO2 materials for the adsorptive removal of Pb(II) in water.

Generating strongly basic sites on magnetic nano-stirring bars: Multifunctional integrated catalysts for transesterification reaction

Mass transfer and catalyst recovery are two crucial issues in solid base catalysis, while the cumbersome operation steps and the associated time and energy penalties are still inevitable for conventional catalysts. Achieving the technical upgrades through catalyst design is desirable but challenging because of the difficulty in satisfying diverse demands of different steps. In this work, a magnetically responsive solid base catalyst with the rod-like nanostructure was developed. The rod-like solid base catalysts are composed of Fe3O4 cores, silica shells and calcium oxide active sites. The functions of magnetic recovery and stirring were integrated into the catalyst, which applies in both the general catalytic processes and microchannel reactors given their nanoscales. When applied to the synthesis of dimethyl carbonate by one-step transesterification of methanol and ethylene carbonate, an apparent enhancement on turnover frequency value (33.1 h−1) was observed for nano-stirring compared with that tested without stirring (12.1 h−1) within 30 min. The present catalysts may open up new avenues in the development of advanced solid base catalysts.

Preparation and characterization of magnetic molecularly imprinted polymer for specific adsorption of wheat gliadin

In this study, a magnetic molecularly imprinted polymers (MIPs) was successfully synthesized by surface imprinting technology for the specific recognition of wheat gliadin (GLI). MIPs showed an obvious hierarchical characteristic by investigations of micromorphology, the magnetic Fe3O4 core were wrapped with SiO2 layer (approximately 40 nm) and imprinted layer (approximately 10 nm). The results of vibrating sample magnetometer (VSM) proved the superparamagnetism of MIPs, which was contributed to the rapid magnetic separation. Furthermore, MIPs displayed excellent selective adsorption ability for GLI through adsorption kinetic model, adsorption isotherm model and adsorption selectivity experiment. The saturated adsorption capacity of MIPs to GLI was 73.55 mg/g under the optimized conditions and the imprinting factor was 3.10. The high performance liquid chromatography (HPLC) manifested that the MIPs were successfully applied to separate template GLI from gluten, reflecting the excellent adsorption specificity of MIPs. Therefore, this research provided a promising method for rapidly separation and specific adsorption of GLI.

Tunable random lasing in Au@Fe3O4, Fe3O4@Au core shell nanoparticles under external magnetic field

This work aims to control the random laser performance using magneto-plasmonic Fe3O4@Au and Au@Fe3O4 core shell nanoparticles as scatterer points in Rh6G dye. For this purpose, nanoparticles were produced via laser ablation in liquid method and mixed together in a dye medium. After characterizing samples through transmission electron microscopy and florescence spectra in the visible region, the samples were pumped via second harmonic generation of Nd: YAG laser and random lasing action were gathered by spectrometer. These measurements were performed with and without external magnetic field in four different magnetic field strengths of 1.08, 2.35, 17.7, and 20.7 mT. Our results revealed good full width at half maximum of laser efficiency in the samples exposed to the external magnetic field. In addition, using the external magnetic field, the samples with larger Fe3O4 core NPs and smaller shell thicknesses indicated a better ability to achieve a tunable random lasing under the external magnetic field.

Magnetic Field-Assisted Fast Assembly of Microgel Colloidal Crystals.

Compared with the colloidal crystals (CCs) of hard spheres, large-scale, high-quality CCs of soft microgel spheres are easier to be assembled because they are more tolerant to defects. However, to assemble microgel CCs, a microgel dispersion should first be concentrated and then allowed to crystallize, which is tedious and time-consuming. Herein, we demonstrated that a magnetic poly(N-isopropylacrylamide) (PNIPAM) microgel with an Fe3O4 core and a PNIPAM shell can be assembled into CCs quickly by simply applying an external magnetic field to the diluted microgel dispersions. The resulting CCs are highly ordered as revealed by their iridescent color, laser diffraction pattern, and confocal characterization. They display a sharp Bragg peak on their reflection spectra, which shifts to lower wavelength when heated because of the thermosensitivity of the PNIPAM shell. The magnetic assembly is not only simple and fast but also allows control of the CC structure in both horizontal and vertical directions. Using spatially varying magnetic fields, patterned microgel CCs were facilely assembled. More importantly, magnetic microgel spheres with different sizes can be assembled in a layer-by-layer manner by adding them sequentially, and the thickness of each layer can be simply controlled by the amount of spheres added.

Use of polyaniline coating on magnetic MoO3 and its effects on material stability and visible-light photocatalysis of tetracycline

A semiconducting material (polyaniline-coated magnetic MoO3) with photodegradative properties and low solubility was synthesized and assessed in the degradation of tetracycline (TC) to address the rising concern of antibiotics in water systems. Polyaniline (PANI) provided a protective coating, significantly reducing MoO3 dissolution across a wide pH range, while the Fe3O4 core facilitated photocatalyst extraction from water. Uncoated MoO3@Fe3O4 dissolution significantly increased with increasing pH (dissolved Mo percentage of 2.9% at pH 3 and 22.9% at pH 10). With the PANI coating, dissolution was reduced to 1.6% at pH 3 and 5.6% at pH 10. The TC removal by PANI@MoO3@Fe3O4 was 8.2 mg TC/g photocatalyst in visible light and 6.5 mg/g in dark within 35 min under optimum conditions. The degradative properties of PANI@MoO3@Fe3O4 toward TC were facilitated by reactive species produced from water oxidation by photogenerated holes (h+). This initial assessment of PANI@MoO3@Fe3O4 as a photocatalyst for pharmaceutical contaminant degradation indicates PANI@MoO3@Fe3O4 is a promising material useful for wider environmental applications.

Porous core–shell Fe3O4@CuSiO3 microsphere as effective catalyst for styrene epoxidation

The porous core–shell Fe3O4@CuSiO3 catalyst were synthesized via a multi-step preparation method including StÖber method and hydrothermal process. The morphological, magnetic and physicochemical studies demonstrated a successful fabrication of the targeted material. This catalyst possessed a spherical morphology with a magnetic core and protective porous shell. The Fe3O4 core not only offered a convenient way for magnetic recycling, but also worked as an electron donor to increase the electron density on the CuSiO3 shell. The catalytic performance of the synthesized material was investigated in the styrene epoxidation with tert-butyl hydroperoxide as oxidant. On account of the synergy effect between Fe3O4 and CuSiO3, the porous core–shell Fe3O4@CuSiO3 catalyst showed styrene conversion significantly higher compared to those of pure Fe3O4, pure CuSiO3 and physically mixed catalyst (Fe3O4 + CuSiO3). In particularly, the catalytic activity of the Fe3O4@CuSiO3 was retained after the recyclability test and re-calcination, which confirmed that the Fe3O4@CuSiO3 catalyst was easily separated, highly stable and could be used six times without significantly affecting its structural order. Moreover, the kinetic study revealed the activation energy of Fe3O4@CuSiO3 in styrene epoxidation was 45.4 kJ/mol. The possible free radical mechanism for the styrene epoxidation based on the Fe3O4@CuSiO3 catalyst was proposed.

Magnetically separable Fe3O4/mZrO2/Ag nanocomposites: Fabrication and photocatalytic activity

In this study, a facile and efficient approach was proposed for fabricating magnetically separable core-shell structured nanocomposites consisting of a magnetic Fe3O4 core, a mesoporous ZrO2 (mZrO2) interlayer and an outer Ag nanoparticles shell using a sol-gel process and a wet chemistry method at ambient condition, and the hydrothermal treatment. The resulting Fe3O4/mZrO2/Ag nanocomposites were analyzed by TEM and SEM images, XPS, EDX and XRD spectra. Their photocatalytic activity was examined for the degradation of methylene blue under UV light. The effect of initial concentration, catalyst dosage and pH value was investigated and the results were discussed. Fe3O4/mZrO2/Ag nanocomposites showed higher photocatalytic activity, compared with Fe3O4/mZrO2 composites. The PL analysis revealed Fe3O4/mZrO2 composites possessed the enhanced separation efficiency of electron-hole pairs in comparison with Fe3O4/mZrO2. Moreover, the Fe3O4/mZrO2/Ag nanocomposites can be easily separated and recycled with an external magnetic field, and so they present remarkable reusability.

Oxidation of ferumoxytol by ionizing radiation releases iron. An electron paramagnetic resonance study.

Ferumoxytol (FMX) is an iron oxide nanoparticle that is FDA approved for the treatment of iron deficiency anemia. FMX contains an Fe3O4 core. Currently, the redox chemistry of Fe3O4 nanoparticles remains relatively unexplored. FMX has recently gained interest as an anti-cancer agent. Ionizing radiation (IR) is a treatment modality employed to treat several types of cancer. Utilizing electron paramagnetic resonance (EPR) spectroscopy, we found that the products produced from the radiolysis of water can oxidize the Fe3O4 core of FMX. Because of the limited diffusion of the HO2• and HO• produced, these highly oxidizing species have little direct effect on FMX oxidation. We have determined that H2O2 is the primary oxidant of FMX. In the presence of labile Fe2+, we found that reducing species generated from the radiolysis of H2O are able to reduce the Fe3+ sites of the Fe3O4 core. Importantly, we also have shown that IR stimulates the release of ferric iron from FMX. Because of its release of iron, FMX may serve as an adjuvant to enhance radiotherapy.

In situ reduction of Ag on magnetic nanoparticles with gallic acid: effect of the synthesis parameters on morphology.

Aim: Synthesis of Fe3O4-Ag composite nanoparticles (NPs) by a new in situ reduction of Ag NPs on the surface of Fe3O4 NPs using gallic acid as a reducing agent. Materials & methods: The influence of process parameters on NP morphology and functionalization was evaluated by means of field-emission scanning/scanning transmission electron microscopy and Fourier-transform IR spectroscopy. Results & conclusion: The synthesis conditions affected the morphology of the obtained NPs, evidence of the formation of polydispersed aggregates, nanoflower-like or nanodumbbell nanocomposites. In particular, well-defined nanodumbbells were obtained in aqueous media, with an NP/gallic acid ratio of 10:1, while the presence of a silica shell did not improve the morphology of Ag NPs nucleated on the Fe3O4 core.

Carbon Double Coated Fe3O4@C@C Nanoparticles: Morphology Features, Magnetic Properties, Dye Adsorption.

This work is devoted to the study of magnetic Fe3O4 nanoparticles doubly coated with carbon. First, Fe3O4@C nanoparticles were synthesized by thermal decomposition. Then these synthesized nanoparticles, 20–30 nm in size were processed in a solution of glucose at 200 °C during 12 h. The morphology and features of the magnetic properties of the obtained hybrid nanoparticles were characterized by transmission electron microscopy, differential thermo-gravimetric analysis, vibrating sample magnetometer, magnetic circular dichroism and Mössbauer spectroscopy. It was shown that the magnetic core of Fe3O4@C nanoparticles was nano-crystalline, corresponding to the Fe3O4 phase. The Fe3O4@C@C nanoparticles presumably contain Fe3O4 phase (80%) with admixture of maghemite (20%), the thickness of the carbon shell in the first case was of about 2–4 nm. The formation of very large nanoparticle conglomerates with a linear size up to 300 nm and of the same regular shape is a remarkable peculiarity of the Fe3O4@C@C nanoparticles. Adsorption of organic dyes from water by the studied nanoparticles was also studied. The best candidates for the removal of dyes were Fe3O4@C@C nanoparticles. The kinetic data showed that the adsorption processes were associated with the pseudo-second order mechanism for cationic dye methylene blue (MB) and anionic dye Congo red (CR). The equilibrium data were more consistent with the Langmuir isotherm and were perfectly described by the Langmuir–Freundlich model.

Versatile core–shell magnetic fluorescent mesoporous microspheres for multilevel latent fingerprints magneto‐optic information recognition

AbstractLatent fingerprints are extremely vital for personal identification and criminal investigation, and potential information recognition techniques have been widely used in the fields of information and communication electronics. Although physical powder dusting methods have been frequently employed to develop latent fingerprints and most of them are carried out by using single component powders of micron‐sized fluorescent particles, magnetic powders, or metal particles, there is still an enormous challenge in producing high‐resolution image of latent fingerprints at different backgrounds or substrates. Herein, a novel and effective nanoimpregnation method is developed to synthesize bifunctional magnetic fluorescent mesoporous microspheres for latent fingerprints visualization by growth of mesoporous silica (mesoSiO2) on magical Fe3O4 core and then deposition of fluorescent YVO4:Eu3+ nanoparticles in the mesopores. The obtained Fe3O4@mesoSiO2@YVO4:Eu3+ microspheres possess spatially isolated magnetic core and fluorescent shell which were insulated by mesoporous silica layer. Due to their small particle size of submicrometer scale, high magnetization and low magnetic remanence as well as the combined magnetic and fluorescent properties, the microspheres show superior performance in visual latent fingerprint recognition with high contrast, high anti‐interference, and sensitivity as well as good retention on multifarious substrates regardless of surface permeability, roughness, refraction, colorfulness, and background fluorescence interference, and it makes them ideal candidates for practical application in fingerprint visualization and even magneto‐optic information storage.image

Adsorptive remediation of organic pollutant and arsenic (V) ions from water using Fe3O4-MnO2 nanocomposite

The presence of various pollutants in water poses a threat to human health. In this study, we focused on the removal of organic pollutant methylene blue (MB) and As(V) from the water by using Fe3O4-MnO 2 nanocomposite. The surface area of the as-prepared nanocomposite was found to be 237.39 m2/g. The nanocomposite was further characterized by using analytical techniques like powder XRD, SEM, VSM and transmission electron microscope. The results of the transmission electron microscope (TEM) showed Fe3O4 cores coated by a MnO 2 shell. VSM analysis showed that the Fe3O4-MnO 2 nanocomposite has ferromagnetic behavior. The efficiency of Fe3O4-MnO 2 nanocomposite for the removal of methylene blue (MB) and As(V) from the water was studied by varying the pollutant concentration and contact time. The results showed a maximum adsorption capacity of 146.1 mg/g for MB and 16.6 mg/g for As(V). The sorption equilibrium data fitted to Langmuir adsorption model for both MB and As(V) adsorption. The nanocomposite was magnetically separable and tested for five consecutive adsorption–desorption cycles. The Fe3O4-MnO 2 nanocomposite retained 70% of its adsorption capacity over five consecutive cycles of regeneration for MB as well as As(V). The result obtained suggest that Fe3O4-MnO 2 nanocomposite can be a promising adsorbent for the removal of methylene blue and As(V) present in water.