Fe3O4 Microspheres Research Articles

Synthesis and electrocatalytic properties of AgxAuy/Fe3O4 composite microspheres and nanoparticles

Two synthetic projects were designed to prepare AgxAuy/Fe3O4 composite microspheres and nanoparticles via one-step hydrothermal method. The as-prepared samples were characterized by using XRD, XPS, TEM and SEM techniques, respectively. The AgxAuy/Fe3O4 composite microspheres had the uniform size with 110 nm or so. The size of AgxAuy/Fe3O4 composite nanoparticles was not uniform and Ag and Au nanoparticles were dispersed in Fe3O4. The AgxAuy/Fe3O4 composite microspheres and nanoparticles were modified on glassy carbon electrodes and their electrocatalytic performances for p-nitrophenol reduction in a base medium were investigated. The results show that Fe3O4 microspheres and nanoparticles mingled with Au showed higher electrocatalytic activity than the pure Fe3O4. As Fe3O4 was loaded with Ag and Au, the electrocatalytic activity of AgxAuy/Fe3O4 composite microspheres increased first then decreased with increasing Ag content, but the activity of AgxAuy/Fe3O4 composite nanoparticles increased with increasing Ag content.

Enhanced reduction and in-situ stabilization of Cr(VI) by Fe3O4@polydopamine magnetic microspheres embedded in sludge-based carbonaceous matrix

In this study, well-defined sludge-based magnetic polydopamine (SMP) was synthesized by a facile and green approach. Pristine activated sludge (PAS) was recycled to be a carbonaceous matrix, represented as sludge-based support (SBS) and used to support bare magnetic Fe3O4 microspheres (BM), which finally gave sludge-based magnetic Fe3O4 microspheres (SM). A lot of BM were further transformed to core–shell structured magnetic Fe3O4@polydopamine microspheres (MP) by polymerization of dopamine. The specific surface areas of SMP were 30.9 m2 g−1, far larger than those of the BM (5.5 m2 g−1) and SBS (2.1 m2 g−1). The maximum adsorption capacity was calculated to be 118 mg g−1 at 323 K. More significantly, reduction-stabilization process of Cr(VI) was found to occur on the surface nanolayered coating. Specifically, after being protonated, the nitrogen atoms contained in SMP were confirmed to attract negatively charged Cr(VI) by electrostatic attraction. The redox system promoted electron transfer from polydopamine (PDA) to Cr(VI), and then the non-protonated nitrogen atoms in-situ chelated the reduction product Cr(III) as coordination atoms. In short, BM supported by the SBS and coated by PDA possessed excellent capability for magnetic separation and reduction–stabilization of Cr(VI), and proved to be a stable and green adsorbent.

Construction of copper (II) affinity- DTPA functionalized magnetic composite for efficient adsorption and specific separation of bovine hemoglobin from bovine serum

In this work, the copper (II) affinity-DTPA (Diethylene triamine pentacetate acid) functionalized magnetic composite was prepared and as an outstanding separation platform to isolate specific bovine hemoglobin (BHb) from bovine serum. Firstly, the Fe3O4 microspheres were prepared via solvothermal method, followed by silanization with TEOS (Tetrathoxysilane) and coating with APTMS (3-Aminopropyl trimethoxysilane). Then incorporating the DTPA ligands via the amino/anhydride reaction. Finally, the target adsorbents (Fe3O4@SiO2@NH2@DTPA@Cu2+ microspheres) were obtained via charging with copper ions. The resulting materials could selectively and specifically isolate BHb with a high maximum capture capacity of 911.3 mg g−1. The absorbed BHb was easily eluted with a recovery of 82.4% by using 0.1 M of Na2CO3-Histidine as eluent. And the real sample analysis of Fe3O4@SiO2@NH2@DTPA@Cu2+ microspheres was also tested using bovine serum, which was identified using MALDI-TOF Ms and SDS-PAGE analysis. The excellent results demonstrate that Fe3O4@SiO2@NH2@DTPA@Cu2+ microspheres would be a good bioseparation material for biomacromolecules like histidine-tagged proteins.

Green production of diosgenin from alcoholysis of dioscorea zingiberensis C. H. wright by a magnetic solid acid

A new method of the catalytic alcoholysis of Dioscorea zingiberensis C. H. Wright into diosgenin by magnetic solid acid in a Teflon-lined stainless-steel autoclave for the first time. The magnetic solid acid, Fe3O4@SiO2–SO3H, was prepared by the connecting the –SO3H groups on the surface of SiO2 encapsulated Fe3O4 microspheres. The synthesized catalysts were systematically analyzed by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analyzer (TGA), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), temperature programmed desorption of ammonia (NH3-TPD), scanning electron microscope (SEM), transmission electron microscope (TEM) and transmission electron microscope-mapping(TEM-mapping). To obtain the best conditions for the alcoholysis of Dioscorea zingiberensis C. H. Wright, single factor test was first utilized to determine the range of optimal conditions and optimized by response surface method. A three-level-three-factor Box-Behnken design was adopted to illustrate the effect of solid acid mass, solvent volume, reaction time and temperature on the yield of diosgenin. The optimum conditions obtained by response surface methodology were: 0.42 g Fe3O4@SiO2–SO3H, 4.38 mL solvent of ethanol, the reaction temperature at 100 °C and 6.09 h reaction time. At the optimal conditions, this method can reach the highest yield 2.64% from Dioscorea zingiberensis C. H. Wright. The yield of the new method was 21.66% higher than conventional sulfuric acid hydrolysis based on the analysis results of UV and HPLC. Importantly, the catalysts and solvents used in the alcoholysis process by the solid acid can be recovered, which is green and environmentally friendly, indicating that the catalytic alcoholysis with magnetic solid acid under hydrothermal conditions had a broad application prospect in diosgenin production.

Fabrication of novel magnetic core-shell chelating adsorbent for rapid and highly efficient adsorption of heavy metal ions from aqueous solution

A novel magnetic core-shell Fe3O4@[epichlorohydrin-co-triethylenetetramine]n-graft-CSSNa microspheres (Fe3O4@[ECH-co-TETA]n-g-CSSNa) was successfully fabricated through adhesion and subsequent crosslinking of poly(epichlorohydrin-co-triethylenetetramine) copolymer ([ECH-co-TETA]n) on Fe3O4 microspheres and then grafting with dithiocarbamate (−CSS−). The as-prepared Fe3O4@[ECH-co-TETA]n-g-CSSNa microspheres presented an uniform core-layer architecture with approximately 600 nm of particle sizes and 50 nm of coating layer. The −CSS− content of Fe3O4@[ECH-co-TETA]n-g-CSSNa was 1.9257 mmol g−1, and its measured magnetization saturation value was 50.51 emu g−1. Benefiting from its unique microstructure, the resulting adsorbent exhibited high adsorption efficiencies of 293.85, 256.69, 277.93, and 225.07 mg g−1 for Pb2+, Cd2+, Cu2+, and Zn2+ in the pH range of 5.00–8.00 at 293 K, respectively, and rapid adsorption speed of reaching equilibrium within 10 min. Meanwhile, the resulting adsorbent could be easily regenerated at least five cycles with a little capacity loss and exhibited excellent magnetic separation performance. The adsorption data fitted the Langmuir and pseudo-second-order models well, and the adsorption activation energies for Pb2+, Cd2+, Cu2+, and Zn2+ were 26.6359, 15.6302, 26.5152, and 21.1095 kJ mol−1, respectively. All adsorption were spontaneous endothermic processes featuring an entropy increase, involving electrostatic attraction, physisorption, and chemisorption (especially ion exchange and surface complexing adsorption). In chemisorption, S, N, and O in the active layer of Fe3O4@[ECH-co-TETA]n-g-CSSNa were all involved in the formation of a coordination bond and particularly formed a symmetrical S-coordinated four-membered ring of (–CSS−)2M2+. Our work suggests a promising strategy for the rapid and highly efficient removal of heavy metal ions from wastewater.

Core-double shell templated Fe/Co anchored carbon nanospheres for oxygen reduction

Propelled by the demand of cost-effective and sustainable electrocatalysts, non-precious catalysts are beginning to spark tremendous interest. Among them, carbon-based materials are able to load various active sites ranging from metallic (Ni, Fe, Co, and Mn) andnon-metallicelements (B, P, S, and N). In this study, a novel reactive core-double shell template strategy was exquisitely designed to synthesize Fe-C and Co-C hybrids anchored on Nitrogen-doped hollow carbon nanospheres (Fe/Co@NDHC). Fe3O4 microsphere plays as the core, and polyaniline (PANI) and zeolitic imidazolate framework-67 (ZIF-67) is the inner and outer shell, respectively. Thanks to the synergistic effect between interconnected multiple active sites and unique porous hollow structure, the as-prepared Fe/Co@NDHC exhibited an outstanding Oxygen Reduction Reaction (ORR) performance with a half-wave potential (E1/2) of 0.918 V in alkaline media, as well as a superior tolerance to methanol and a long-term stability. The synergetic effects of Fe-C, Co-C and pyridinic-N active sites were further confirmed by density functional theory calculations. This reactive templated method offers a new way to fabricate heteroatom doped materials with a controlled morphology for diverse energy-related applications.

Microwave absorption enhancement of e-Fe3O4@C microspheres by core surface modification

Abstract Magnetic particles can be combined with carbon materials to prepare core-shell microwave absorbers and the proper core/shell weight ratio yields the optimal absorption effects. However, few studies have focused on the influence of core surface modification on the microwave absorption performance. In this work, e-Fe3O4@C composite microspheres are synthesized by surface etching of core Fe3O4 microspheres in HCl followed by polymerization/carbonization. Core surface modification improves the microwave absorption capability of the e-Fe3O4@C microsphere films. The minimal reflection loss (RLmin) is −54.38 dB at 12.4 GHz for a film thickness of 2.6 mm and the maximum effective bandwidth is extended to 4.1 GHz (3 mm). Etching of the Fe3O4 core surface increases the interfacial contact area consequently enhancing interface polarization and defects created by surface etching produce additional dipole polarization to further increase the dielectric loss. The underlying mechanism is investigated and described. The results reveal a novel and effective strategy to enhance the properties of core-shell microwave absorption materials.

Electroactive magnetic microparticles for the selective elimination of cesium ions in the wastewater

To improve operability as well as the removal efficiency for cesium ions in the wastewater treatment, a novel electrochemically switched ion exchange (ESIX) technique by using electroactive Prussian-blue(PB)-based magnetic microparticles (PB@Fe3O4 microparticle) with different uniform particle sizes in the range of 300–900 nm as the adsorption materials was developed. The obtained PB@Fe3O4 microparticle were characterized by Scanning electron microscopy (SEM), Transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and Thermogravimetric analysis (TGA). It is found that the PB can be well coated on the surface of Fe3O4 microsphere, which can be easily adsorbed on the magnetic electrode substrate for the electrochemical adsorption of Cs+ ions. Electrochemical adsorption of 97% Cs+ on PB/Fe3O4 was achieved in less than 10 min, and the maximum adsorption capacity was 16.13 mg/g, and the distribution coefficient (KD) of Cs+ ions reached as high as 3938. In addition, the electrochemical adsorption behavior of PB@Fe3O4 microparticle fitted well with the Freundlich adsorption isotherm and the Pseudo-second-order kinetic models. It is expected that such an ESIX technique using PB@Fe3O4 microparticle can be applied for the separation and recovery of dilute Cs+ ions from cesium-contaminated solution in a practical process.

Evaluation of Different Blood Circulating miRNAs for Hepatocellular Carcinoma Diagnosis.

The current study was conducted to investigate the potential of three circulating miRNAs (miR-21, miR-16 and miR-100) as HCC diagnostic marker in the population living in Guangdong province, China. First, the Fe₃O₄ and Fe₃O₄@SiO₂ magnetic microsphere were prepared. Fe₃O₄@SiO₂ microspheres were further used for total RNA purification from serum. After that, the real-time qPCR was conducted for the detecting the miRNA in the serum of HCC patients and healthy volunteers. Scanning electron microscope and transmission electron microscope images showed that monodisperse Fe₃O₄ and Fe₃O₄@SiO₂ microspheres were successfully synthesized with a mean diameter of about 500 nm and 600 nm, respectively. The microsphere was spherical in shape with good state of dispersion. The characteristic peak at 1088.8 cm-1 in FTIR spectra belonged to the asymmetry stretching vibration of Si-O-Si, which confirmed the SiO₂ coating on Fe₃O₄ microspheres. The successful amplification of miRNAs in qPCR verified that the total RNA extracted using the Fe₃O₄@SiO₂ microspheres retained high quality. The real time PCR results showed that miR-21 was differentially expressed in the serum of HCC patients and healthy volunteers. miR-21 and alpha-fetoprotein (AFP) together could be potentially used as HCC diagnostic marker in Guangdong province population in China.

Manganese-Promoted Fe3O4 Microsphere for Efficient Conversion of CO2 to Light Olefins

In this work, manganese well-dispersed on Fe3O4 microsphere (Mn–Fe3O4) catalyst was synthesized. It exhibited excellent catalytic performance for the direct conversion of carbon dioxide (CO2) into light olefins. A CO2 conversion of 44.7% with high selectivity of light olefin (46.2%, yield of 18.7%), high O/P ratio (6.5), and low selectivity of CO (9.4%) was obtained over the 10Mn–Fe3O4 catalyst. The Mn–Fe3O4 catalyst was studied by XRD, SEM, (HR)TEM, STEM–EDS, H2-TPR, and CO2-TPD. The result indicated that the manganese promoter could facilitate the adsorption of CO2 and the activation of C═O bonds as well as inhibit the secondary hydrogenation. This work offered a novel Fe-based catalyst system to the utilization of CO2 and an understanding in promoting C═O bond activation in the first step of CO2 hydrogenation to hydrocarbon reaction.

Construction of hierarchical SnO2@Fe3O4 nanostructures for efficient microwave absorption

A hierarchical sea-urchin-like SnO2@Fe3O4 nanostructure was synthesized via a simple two-step liquid-phase method. The SnO2 nanorod epitaxially grew in the radial direction on the surfaces of Fe3O4 microspheres. The microwave absorbing properties of the hierarchical SnO2@Fe3O4 nanostructure were studied. The hierarchical SnO2@Fe3O4 nanostructure showed enhanced microwave absorbing properties compared to those of the primary Fe3O4 microspheres. The maximal refection loss (RL) of the hierarchical SnO2@Fe3O4 nanostructures was −20.0 dB at 14.5 GHz with an absorber thickness of 8 mm. These results demonstrate an efficient method for designing new types of microwave-absorbing materials with high performances.

Removal and recovery of phosphate and fluoride from water with reusable mesoporous Fe3O4@mSiO2@mLDH composites as sorbents

Three core/shell/shell MgAl-LDH composites using Fe3O4 microspheres as the core, a SiO2 matrix as the inner layer and a MgAl-LDH layer as the outer shell have been synthesized for the removal and recovery of phosphate and fluoride from water by a magnetic separation technique. The synthetic mesoporous MgAl-LDH composites show good magnetic separability, well-defined pore distributions, and have specific surface areas of 73 m2 g−1, 168 m2 g−1, and 137 m2 g−1 for Fe3O4@SiO2@LDH350, Fe3O4@SiO2@mLDH350, and Fe3O4@mSiO2@mLDH350, respectively. The adsorption isotherms of both phosphate and fluoride on these MgAl-LDH composites can be well fitted with the Langmuir model. The maximum adsorption capacities of 57.07 mg g−1 and 28.51 mg g−1 were obtained on Fe3O4@mSiO2@mLDH350 for phosphate and fluoride, respectively, much higher than those of other LDH-type materials. The adsorbed phosphate and fluoride could be successfully recovered by NaNO3-NaOH solution, and the regenerated MgAl-LDH composites could be reused for phosphate and fluoride removal. Owing to their high adsorption capacities of both phosphate and fluoride, easy magnetic separation from solution, and good reusability, the mesoporous MgAl-LDH composites are expected to have potential applications in removal or recovery of fluoride or phosphate from water.

One-pot formation of magnetic layered double hydroxide based on electrostatic self-assembly to remove Cr(VI) from wastewater

Magnetic ZnAl-LDH composite materials (Fe3O4@LDH) based on the electrostatic attraction was manufactured by self-assembly method to remove Cr(VI) from wastewater simultaneously. Fe3O4 microspheres with suitable size can be surrounded by the LDH layers in the formation process to separate easily and reduce the dosage of Fe3O4. The removal behaviors of Cr(VI) from wastewater were investigated and the obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopic (TEM) and molecular simulation. Equilibrium studies indicated that the experimental data was well described by Langmuir models and the removal was a charge-limited process. Compared with other reported papers, the removal capacity for Cr(VI) by this method was larger, revealing a maximum utilization of charges on LDH. By molecular simulation, the relationship among chemical bond, electron transfer and energy was explained microscopically and the removal mechanism was proved that Cr(VI) trapped onto Fe3O4@LDH involved ion electrostatic interaction. The reusability of Fe3O4@LDH composite was tested and illustrated that it can be reused for several times.

Integration of Fe3O4@UiO-66-NH2@MON core-shell structured adsorbents for specific preconcentration and sensitive determination of aflatoxins against complex sample matrix

Aflatoxins have been a hot topic in the field related into public health and ecosystem protection, and great effort has been made in developing of adsorptive materials for effective probing the target aflatoxins. Conventional materials, like metal-organic frameworks (MOFs) showed promising application in separation science. However, the cumbersome separation process, competitive adsorption are also major challenges. Regarding this, a novel magnetic micro-composite denoted as Fe3O4@UiO-66-NH2@MON with core-shell structure was constructed. The core of Fe3O4 microspheres was coated with MOFs crystals, and then microporous organic network (MON) was introduced onto the surface of Fe3O4@UiO-66-NH2 through a sonogashira coupling reaction. It exhibited good magnetic separation ability, which effectively simplified the pre-treatment steps. The proposed method possessed excellent selectivity and sensitivity, with detection limits in the range of 0.15-0.87 μg L−1 combination with HPLC analysis. More importantly, the MON coating significantly improved the hydro-stability of whole adsorbents, thus enhancing the adsorption efficiency and favoring the practical application of the materials. The developed Fe3O4@UiO-66-NH2@MON-based solid extraction method has been well-applied for real sample analysis, with the recovery of 87.3%–101.8%. We believe the newly-constructed hybrid nano-adsorbents hold great potential in further application in various analytical methods for different target analytes.

Enhanced removal of fluoride and arsenate ions from aqueous solution by magnetic Mg–Al composite oxides (Fe3O4@Mg–Al–O)

Herein, magnetic Mg–Al composite oxides (Fe3O4@Mg–Al–O) as an effective adsorbent were successfully prepared. And the magnetic Fe3O4 microspheres could improve the separability and removal ability, which were loaded onto the surface of Mg–Al–O. The adsorption behaviors of Fe3O4@Mg–Al–O for fluoride (F−) and arsenate ions [As (V)] were studied by static adsorption experiments, such as initial pH, contact time, co-existing ions, and so on. The equilibrium isotherms and kinetics data for F− and As (V) adsorption were best fitted with Freundlich isotherm and pseudo-second-order kinetic. The maximum adsorption capacity for F− and As (V) were 170.02 mg·g−1 and 146.22 mg·g−1, respectively, showing the perfect absorption capability of an adsorbent. Fe3O4@Mg–Al–O showed better adsorption performance for F− and As (V) at optimum pH of 4.0-9.0. Moreover, the removal mechanism of F− and As (V) was the surface hydroxyl groups (M-OH) exchanged with the F− and As (V).

Facile fabrication of Au/Fe3O4 nanocomposites as excellent nanocatalyst for ultrafast recyclable reduction of 4-nitropheol

A highly efficient Au/Fe3O4 nanocatalyst is fabricated by using a seed deposition method, and is characterized by XRD, TEM, EDS, XPS, UV–vis and VSM, respectively. TEM image shows that small Au nanoparticles are immobilized onto Fe3O4 surface uniformly and densely. After immersion treatment by NaBH4, the Au/Fe3O4 nanocatalyst exhibits high catalytic efficiency in reducing 4-nitrophenol to 4-aminophenol. The 4-nitrophenol could be fully degraded in less than one minute. The Au/Fe3O4 nanocatalyst demonstrate good magnetic recoverability and high conversion in 1 min (>98%) after 8 successive cycles. The reaction rate constant k of the catalyst with volume Au sol/mass Fe3O4 microspheres ratio 3 (Au/FeO-3) is 13.8 min−1, which is 4.7 times larger than that of Au/FeO-1. The catalytic mechanisms were discussed. This work provides a simple and environmentally friendly method for preparing magnetic noble nanocatalyst used for 4-nitrophenol reduction.

Conductive-network enhanced microwave absorption performance from carbon coated defect-rich Fe2O3 anchored on multi-wall carbon nanotubes

Electron conduction capability plays an extremely important role in the field of electromagnetic wave energy conversion. Herein, a novel dual-conductive-network hybrid material was successfully synthesized, where carbon coated defecr-rich Fe2O3 anchored on multi-wall carbon nanotubes (MWCNTs). The entangled MWCNTs serve as a carbon skeleton to support the porous Fe2O3 particle, coating by the ligand-derived conductive carbon. Decorated carbon layer not only acts as a link to connect the Fe2O3 and MWCNTs, but also furnish a new electronic transmission path. Related electromagnetic parameters and electron transportation behavior can be effectively adjusted and controlled via tuning carbon substrate content. Meanwhile, the typical defects and charge density distribution in this C@Fe2O3@MWCNTs system were proved by geometric phase analysis and electron holography technology. This ternary composite can be a potential excellent microwave absorber with a special conductive-netlike structure and multi-interface architecture, benefiting to the conductivity loss and interfacial polarization between porous Fe2O3 microspheres with carbon materials. The optimal reflection value of microwave loss is −49.9 dB at 10.0 GHz with the absorber thickness of 2.0 mm. The as-prepared C@Fe2O3@MWCNTs composites exhibit high-performance microwave absorption and cater to the highly efficient attenuation capability, thin thickness, and lightweight requirements for modern microwave absorption materials.

Facile synthesis of hierarchically structured flower-like Fe3O4 microspheres for high-performance magnetorheological fluids

In this study, flower-like Fe3O4 microspheres with hierarchical structure were prepared by a one-step solvothermal method, and the obtained flower-like Fe3O4 microspheres were adopted as a new magnetorheological (MR) material to prepare a uniform MR suspension with high performances. The synthesized samples were systematically examined using FE-SEM, TEM, TGA, XRD, XPS, BET and VSM. The prepared flower-like Fe3O4 microspheres-based MR fluid indicated typical MR properties, as evidenced by the fact that shear stress, yield stress, viscoelastic storage modulus and loss modulus of MR fluid strongly depended on magnetic field strengths. Specifically, the resultant MR fluid showed good sedimentation stability with sedimentation ratio of 86.5% in the settling period. The excellent sedimentation stability could be attributed to the unique flower-like hierarchical structure, high specific surface area and the reduced particle-fluid density mismatch.

A rapid and efficient method for N-termini analysis in short-lived proteins

A rapid and efficient method to isolate global N-termini is presented. Utilizing laser-assisted proteolysis and Fe3O4 microsphere, protein N-termini could be isolated in 4 h. The amino-blocked protein was digested by trypsin assisted by laser radiation, shortening the digest time from overnight to 40 s. Non-N-terminal peptides were characterized by a tryptic free amino in their N-term, which could be derived with sulfhydryl by traut’ s reagent efficiently and then coupled with Fe3O4 microspheres nearly completely in less than 4 h. The rapid method was beneficial for the identification of unstable N-termini in short-lived proteins. Human serum albumin was studied as a model. The N-terminus was successfully isolated from the digest within 4 h. Also, 2011 N-terminal peptides out of 936 proteins in mouse liver proteome sample were identified using liquid chromatography-tandem mass spectrometer (LC-MS/MS). This method was demonstrated as a facile and efficient N-termini enrichment method for targeted protein N-termini analysis, especially those with short half-life.

Hollow Fe3O4 microspheres/graphene composites with adjustable electromagnetic absorption properties

Fe3O4@rGO composites, consisting of monodisperse hollow Fe3O4 microspheres with an average particle size of 320 nm and reduced graphene oxide, were prepared by using a facile and efficient two-step solvothermal method. Compositions, microstructure and electromagnetic properties of the Fe3O4@rGO composites were systematically studied by using various analytical techniques. Compared with the hollow Fe3O4 and bare rGO, the Fe3O4@rGO composites have significantly higher electromagnetic absorption performances. A maximum reflection loss (RL) of −49.8 dB was achieved at 8.48 GHz, with a wide bandwidth of 3.3 GHz from 6.6 GHz to 9.9 GHz, when the Fe3O4@rGO composites with a Fe3O4 to rGO mass ratio of 2:1 were synthesized at 200 °C for 7 h by using ethylene glycol as the hydrothermal solvent. The absorption covered the mid-low frequency X-band, while the optimum match thickness was 3.0 mm. The peak position of the minimum reflectance of the Fe3O4@rGO composites shifted to lower frequencies with increasing content of Fe3O4. The electromagnetic absorption properties of the Fe3O4@rGO composites could be adjusted by controlling the mass ratio of the two components, reaction time and the sample thickness. SuchhHollow Fe3O4 microspheres/graphene composites could be used as light-weight microwave absorption materials at the mid-low frequency bands.