Magnetic Carbon Composites Research Articles

High-performance pinecone-like MOF derivative electromagnetic wave-absorbing composite via in situ anisotropic-oriented growth

Designing multihierarchical electromagnetic wave-absorbing composite with multiphase, multieffective, and multidimensional properties is an effective way to improve absorption performance. Metal–organic frameworks (MOFs) have a high metal content and a stable carbon framework. By adjusting the metal type, organic ligand type, and precursor ratio during the preparation process, MOF materials with different morphologies can be synthesized and transferred into multihierarchical electromagnetic wave-absorbing composites via in situ pyrolysis. Herein, based on the Kirkendall diffusion effect, an in situ anisotropic-oriented growth strategy was advanced during the pyrolysis of Prussian blue, and a new magnetic carbon composite (γ-Fe2O3 @N-rGO/MWCNT) was prepared. The composite has a multihierarchical structure consisting of pinecone-like nanoflowers and a porous carbon framework. The nanoflowers are core-shell structures with γ-Fe2O3 magnetic nanoparticles as cores and nitrogen-doped reduced graphene oxides as shells interspersed in a porous carbon framework that includes intertwined multiwalled carbon nanotubes and amorphous carbon. The minimum reflection loss (RLmin) of the samples can reach up to − 59.2 dB at 5.51 GHz. The in situ anisotropic-oriented growth strategy used in this work shows great promise for the preparation of a variety of multihierarchical structure nanocomposite electromagnetic wave-absorbing materials with abundant absorption effects.

A magnetic sludge carbon combined persulfate-based ISCO system for leachate-contaminated groundwater remediation

Activation of persulfate by a green magnetic Steel Converter Slag-Sludge Carbon composite (SCS@SC) and subsequent remediation of actual leachate wastewater was studied in an intermittent reactor and column system to assess the potential of the persulfate-based in situ chemical oxidation (SR-ISCO) system for combined oxidative-reductive removal of organic contaminants from groundwater. In the batch experiment, an iron leaching concentration of 6942 mg/L, was higher than 223.2 and 124.4 times that of steel converter slag (31.14 mg/L) and sole sludge carbon (55.80 mg/L). In the column experiments, the total organic carbon (TOC) removal was maintained at 41.7 %, the loading rate reached 48.86 % with 15 g SCS@SC and 0.15 M persulfate after 400 min. The persulfate consumption, sulfuric acid generation, free radical generation, and iron ions flow out under acidic conditions, which are consistent with TOC removal. The mechanism of persulfate activation and organic matter removal was discussed and proposed by electron paramagnetic resonance (EPR) and energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and gas chromatography-mass Spectrometry (GC–MS) to characterize the chemistry of solid and aqueous phases. A mechanism for contaminant removal was presented, which involves free radicals of persulfate activation by zero-valent iron (Fe0) and iron carbide (Fe3C) and precipitation removal by iron oxides. According to the findings, a viable alternative method for the inexpensive synthesis of catalysts from solid wastes such as sludge and steel converter slag was developed.

A novel synthesis method of magnetic porous carbon composites for microwave absorption

A novel combined process of sol-gel method and subsequent in-situ pyrolysis was proposed to prepare magnetic porous carbon composites. Wheat flour was used as the raw material to prepare porous carbon matrix, and three composites doped with different magnetic metals (Co, Ni and Fe20Ni80) were prepared through adding different metal salts to wheat flour. The three composites show similar morphologies and are composed of porous carbon matrix and magnetic metal particles embedded in the matrix. Porous carbon matrix optimizes impedance matching and provides dielectric loss and multiple reflection and diffraction loss to incident electromagnetic waves. Magnetic metal particles endow the composites with ferromagnetic characteristics and magnetic loss ability. The three composites all exhibit outstanding microwave absorption performance and have the potential to become microwave absorbing materials.

Production of Mesoporous Magnetic Carbon Materials from Oily Sludge by Combining Thermal Activation and Post-Washing.

In this work, the oily sludge (OS) from a local waste oil recycling plant was reused as a precursor for producing porous magnetic carbon composites (CC) by pyrolysis, followed by carbon dioxide activation. Based on the thermogravimetric analysis (TGA) of the OS feedstock, the preparation experiments were performed at 800–900 °C. From the pore analysis of the CC products, it indicated an increasing trend, as the BET surface area greatly increased from about 1.0 to 44.30 m2/g. In addition, the enhancement effect on the pore properties can be consistently obtained from the acid-washed CC products because the existing and new pores were reformed due to the leaching-out of inorganic minerals. It showed an increase from 32.27 to 94.45 m2/g and 44.30 to 94.52 m2/g at 850 and 900 °C, respectively, showing their mesoporous features. These porous and iron-containing features were also observed by the scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). In addition, the adsorption removal of total organic carbon (TOC) in the raw wastewater, by the CC product, showed its high performance (>80%).

Magnetic porous carbon composites for rapid and highly efficient degradation of organic pollutants in water

A magnetic porous carbon composite (MPC) was prepared from metal−organic frameworks (MOFs) by the one-step calcination method. The MPC was characterized by SEM, TEM, TG, DTG, Raman and XPS. The adsorption and degradation performance of MPC towards four organic dyes were investigated. The maximum adsorption amount of magenta on MPC was 191.94 mg g -1 at 25 °C. Furthermore, the MPC showed remarkable stability for it can be recycled 5 times through the facile magnetic separation without obvious loss of activity. The degradation efficiency of MPC toward four kinds of organic pollutants was nearly 100% within 36 ​min, which was much higher than that previously reported. • Magnetic Porous Carbon Composites is prepared by one step carbonization with excellent adsorption and catalytic degradation performance. • Maximum adsorption capacity of magenta on MPCs is 191.94 ​mg ​g −1 and nearly 100% degradation efficiency within 36 ​min. • Ultra-fine nanocrystalline Fe 3 O 4 nanoparticles embedded in the octahedral structure, are favor of removal and degradation of organic dye pollutants. • Carbon layer in MPCs is beneficial to avoid secondary pollution in degradation and contribute the stability and recyclability of MPCs. • MPCs possesses potential green and effective application of organic pollutants treatment in complex matrix.

Amino-modified magnetic glucose-based carbon composites for efficient Cr(VI) removal

Background: Biomass materials are currently attracting more research interests as pollutant adsorbent attributed to rich sources, low cost, non-toxicity, biodegradability and easy modification.Methods: Herein, a glucose-based carbon material (GC) was fabricated via hydrothermal method and formed pores materials by activation using KOH. Then the amino modified magnetic glucose-based carbon composite (MAGC) was prepared by the co-precipitation method and followed the simple cross-linking reaction.Significant Findings: MAGC had a high nitrogen content of 10.89 wt.% with many active adsorption sites and the magnetic separation process of MAGC was completed within 25 s. The adsorption experiments indicated the superior adsorption capacity of MAGC for water pollutants (several heavy metal ions and anionic dyes). Cr(VI) was selected as the model pollutant, the maximum adsorption capacity (Qmax) of MAGC was 537.63 mg g−1 at pH 2 and 25 °C, which followed the pseudo-second-order model and Langmuir isotherm model. Low concentration (1 mg L−1) cyclic adsorption demonstrated that after 40 cycles without regeneration, the Cr(VI) concentration remained the below 0.05 mg L−1 in 30 min, which was the safe level of drinking water specified by WHO. This design of biomass-based carbon composites may provide a promising absorbent for efficient removal of water pollutants.

Heterogeneous catalytic oxidation of tetracycline hydrochloride based on persulfate activated by Fe3O4/MC composite

In this study, a novel magnetic mesoporous carbon composite (Fe3O4/MC) was prepared by manganese carbonate (MnCO3) as the template to activate persulfate (PS) for tetracycline hydrochloride (TC) degradation. The characterization results showed that Fe3O4 nanoparticles were evenly distributed on the surface of MC, and Fe3O4/MC had the large surface area of 433.88 m2∙g−1. When the initial TC concentration was 50 mg·L−1, Fe3O4/MC dosage was 0.0336 g, PS dosage was 0.0476 g and the reaction temperature was 30 °C, Fe3O4/MC + PS system could degrade 92.9% of TC within 90 min. TC degradation efficiency increased with the increase of Fe3O4/MC dosage and temperature, but decreased with the increase of TC initial concentration and pH value. The increase of PS concentration first improved TC degradation efficiency, and then was not conducive to its degradation. The quenching experiments indicated that the sulfate radical (SO4•−), superoxide radical (•O2–) and singlet oxygen (1O2) in Fe3O4/MC + PS system contributed to TC degradation. Meanwhile, the toxicity evaluation of the degradation products confirmed that the toxicity of TC in Fe3O4/MC + PS system was greatly reduced. Totally, this study systematically investigated the performance of the Fe3O4/MC + PS system for TC removal, laying a theoretical and practical foundation for treatment of potential antibiotic wastewater (ppm range) in the future.

Magnetic Carbon Composites Derived from Coal Hydrogasification Residue for Microwave Absorption

To cut the cost of microwave absorption materials (MAMs) and achieve the recycling of semicoke (SC), the by‐product in coal hydrogasification process, SC was applied to prepare composite MAMs. The facile synthesis process involves liquid‐phase impregnation, and then in situ carbothermal reduction treatment. Champion sample prepared under 800 °C (FeSC800) exhibits the minimum reflection loss (RLmin) of −39.3 dB under a coating thickness of 2.5 mm, and the effective absorption bandwidth (EAB) can reach 3.9 GHz (14.1–18 GHz) at a coating thickness of 1.5 mm. The enhancement of interfacial and dipole polarization, as well as the synergistic effect between the dielectric properties of SC matrix and the magnetic properties of Fe particles, can account for the excellent microwave absorption (MA) performance. In view of the source of SC matrix, the prepared FeSC800 was not only expected to become a candidate in the field of MAMs, but also presented a promising approach for the resource utilization of SC.

Preparation and Characterization of Porous Carbon Composites from Oil-Containing Sludge by a Pyrolysis-Activation Process

Large amounts of oil-containing sludge (OS) are produced in the energy, industry and services sectors. It is mainly composed of residual oil and particulate matter, thus posing an environmental threat and leading to resource depletion if it is improperly handled. In this work, the OS feedstock was thermally treated to produce porously magnetic carbon composites (CC) using a pyrolysis-activation process. Using the data on the thermogravimetric analysis (TGA) of the OS feedstock, the thermal activation experiments were performed at 850 °C as a function of residence time (30, 60 and 90 min). The results of pore analysis for the resulting CC products showed that the Brunauer–Emmett–Teller (BET) surface area greatly decreased from 21.59 to 0.56 m2/g with increasing residence time from 30 to 90 min. This decline could be associated with continuous gasification by CO2, thus causing the removal of limited carbon on the surface of CC for a longer reaction time. Furthermore, the physical properties of the resulting CC products can be enhanced by post acid-washing due to the development of new pores from the leaching-out of inorganic minerals. The BET surface area increased from 21.59 to 40.53 m2/g at the residence time of 30 min. Obviously, the resulting CC products were porous materials with mesopores and macropores that were concurrently formed from the thermal activation treatment. These porous features were also observed by scanning electron microscopy (SEM).

3-D hierarchical urchin-like Fe3O4/CNTs architectures enable efficient electromagnetic microwave absorption

Three-dimensional (3-D) hierarchical urchin-like Fe3O4/CNTs architecture was synthesized through a simple one-pot hydrothermal method. The urchin-like Fe3O4 was assembled from a large number of nanorods with a diameter of ∼10 nm and a length of ∼100 nm. The introduction of CNTs in urchin-like Fe3O4 greatly improves the dielectric properties and impedance matching of architecture. The as-synthesized Fe3O4/CNTs architecture delivered excellent EMW absorption properties with a reflection loss (RL) of −56.8 dB at 11.12 GHz and a thin thickness of 2.15 mm. The excellent EMW absorption performance of hierarchical Fe3O4/CNTs architecture may be attributed to the synergistic effect of interfacial polarization, conduction loss, eddy current loss, natural resonance, and multiple reflection/scattering. This study paves a robust strategy of 3-D hierarchical structure design to effectively enhance the EMW absorption performance of magnetic carbon composite.

Metal–organic framework derived magnetic carbon Ni@C octahedron composite as an excellent microwave absorber

Metal–organic framework (MOF)-derived magnetic carbon composites have become ideal candidates as high-performance microwave-absorbing materials. Herein, the MOF-derived Ni@C octahedron composite was synthesized via a facile solvothermal reaction and annealing treatment, which involved a material transition process from the Ni–MOF into the magnetic Ni@C composite. The structural, morphological, magnetic, and electromagnetic (EM) properties of as-prepared MOF-derived Ni@C materials were determined. Given the MOF template and controlled carbonized treatment, the obtained micro-scale Ni@C octahedron showed adjustable EM parameters and EM wave absorption property by adjusting the addition amount. The optimized reflection loss value of MOF-derived Ni@C reached −51.9 dB at 10.5 GHz at 2.5 mm thickness, and the composite had broadband microwave attenuation and covered 5.6 GHz from 8.9 GHz to 14.5 GHz. Given the good impedance matching, special spatial structure, and synergy effect between magnetic and dielectric losses, this MOF-derived magnetic carbon Ni@C octahedron composite is expected to be a potential EM wave-absorbing material.

Simultaneous analysis of multiple pesticide residues in tobacco by magnetic carbon composite-based QuEChERS method and liquid chromatography coupled to quadrupole time-of-flight mass spectrometry

Magnetic carbon composite (Fe3O4@C) was synthesized and applied as a reversed-dispersive solid-phase extraction sorbent for the simultaneous analysis of 40 pesticide residues in tobacco by ultrahigh-performance liquid chromatography coupled to quadrupole time-of-fight mass spectrometry. Compared to the traditional QuEChERS method, the optimized Fe3O4@C simplified clean-up process and exhibited better clean-up capability than conventional sorbents. The pesticides were qualitatively identified by accurate mass of protonated molecules, fragment ions, isotopic peak clusters, and retention time, and quantitatively determined by matrix-matched external standard method. Good linearity of the proposed method was obtained with R value greater than 0.997 for all target pesticides at concentration levels of 2–200 µg/L. The limit of detection ranged from 0.14 to 2.67 µg/kg. The recoveries and relative standard deviations of all target pesticides at three spiked concentrations of 20, 50 and 200 µg/kg were in the ranges of 80.8%–113.3% and 0.6%–16.3%, respectively. Compared with the reported methods for the analysis of multiple pesticide residues in tobacco, the proposed method has the advantages of simple to operate, high clean-up ability and less time-consuming in clean-up process.

Efficient adsorption removal of organic nitrogen pesticides: Insight into a new hollow NiO/Co@C magnetic nanocomposites derived from metal-organic framework

The removal of pesticides is a prerequisite for reducing potential threat to environmental safety. It is significant to exploit some adsorbents with excellent adsorption performance, facile separation and recovery. Metal-organic framework (MOF)-based magnetic nanocomposites have received extensive attention in terms of pollutant adsorption. Thus, a new hollow NiO/Co@C magnetic nanocomposites derived from MOF was successfully assembled via simple solvothermal reaction, in which cobalt (Co) ions as inducers to conduct the formation of hollow MOFs by regulating the chemical transformation process, and benefiting from its coordination effect, the carbonized bimetallic Ni-Co-MOF were transformed into magnetic-carbon composites by maintaining its initial skeleton without the tedious preparation of Fe3O4. The hollow structure can accelerate the mass transfer efficiency and the magnetism is conducive to rapid and convenient separation. The composite was used as magnetic solid-phase extraction (MSPE) adsorbent and the adsorption removal of organic nitrogen pesticides (ONPs) for the first time. NiO/Co@C contained hollow porous structure, resulting in high pesticides adsorption performance, as high as 62.2 mg g−1. Furthermore, the adsorption properties and mechanisms of ONPs had been discussed in detail including adsorption dynamics and thermodynamics. More importantly, NiO/Co@C could not only realize easy solid–liquid separation, but also demonstrate excellent reusability and stability. After nine cycles and the extraction recovery still retained higher than 90%. Therefore, NiO/Co@C has great promise as an effective adsorbent for pretreatment of aqueous samples and removal of hazardous pollutants.

Facile route for synthesis of Fe0/Fe3C/γ-Fe2O3 carbon composite using hydrothermal carbonization of sugarcane bagasse and its use as effective adsorbent for sulfamethoxazole removal

Non-toxic mesoporous magnetic carbon composite was synthesised from hydrothermal carbonization of sugarcane bagasse with Iron (III) nitrate nonahydrate in two steps along with thermo-chemical oxidation process using sodium hydroxide. IR spectrum exposed the presence of oxygenated functional groups and FeO whereas XRD analysis revealed the availability of Fe0/Fe3C/γ-Fe2O3 at varying intensities. SEM analysis showed the spherical shaped carbon is well encapsulated with iron particles. Textural studies showed that after thermo-chemical activation intensified the surface area on composites to about 491.474 m2 g−1 thereby, promoting improved porosity on the carbon matrix. The fabricated composite showed magnetization of 32.84 emu g−1 and SMX adsorption capacity as 169.49 mg g−1. Kinetics and isotherm studies revealed that removal of SMX fitted well in Pseudo-second order and Langmuir models. The mode of interaction of SMX on magnetic carbon composites with respect to different pH was studied showing that π-π electron donor interaction (EDA), hydrophobic interaction, charge assisted hydrogen bond formation were responsible for SMX removal. The selectivity nature of magnetic composite with respect to SMX was studied in the presence of multiple pollutant. Use of magnetic carbon helps in industrialising the material to high level due to their unique property in separation and recycling. Application of hydrothermal carbonization is found to be applicable for wet solid substance thereby evolving structural carbon compound.

Direct upcycling of polyethylene terephthalate (PET) waste bottles into α-Fe2O3 incorporated MIL-53(Al) for the synthesis of Al2O3/Fe3O4-encapsulated magnetic carbon composite and efficient removal of non-steroidal anti-inflammatory drugs

The upcycling of polyethylene terephthalate (PET) waste into high-value-added materials can have a significant contribution to global environmental protection. In this study, considering the unique thermal behaviors of PET and metal salts (i.e., Al and Fe) under similar hydrothermal conditions, we proposed a novel solvent-free one-pot approach for the upcycling of PET. In a one-pot hydrothermal reaction at 220 ℃ under self-generated pressure, PET waste was depolymerized into starting monomers (terephthalic acid and ethylene glycol), Al-based metal–organic frameworks (MIL-53(Al)) were fabricated, and iron oxides (α-Fe2O3) were formed simultaneously. X-ray diffraction measurements clearly demonstrated that α-Fe2O3 incorporated MIL-53(Al) (α-Fe2O3/MIL-53(Al)) was successfully synthesized directly from PET waste bottles via a novel green approach. After the annealing process, the α-Fe2O3/MIL-53(Al) precursor was successfully converted to an Al2O3/Fe3O4-encapsulated magnetic carbon composite (Al/[email protected]). The feasibility test proved that the Al/[email protected] prepared at an annealing temperature of 600 ℃ (Al/[email protected]600) effectively removed four common non-steroidal anti-inflammatory drugs, i.e., ibuprofen (96.31%), diclofenac (66.84%), naproxen (87.83%), and ketoprofen (90.07%). Owing to its low removal rate, diclofenac was selected as the target pollutant, and the adsorption parameters were optimized using response surface methodology. Under the optimized conditions (solution pH = 5.0, adsorbent dosage = 1.21 g/L, and contact time = 15 h), the maximum actual diclofenac removal (92.94%) was obtained, which agreed with the maximum theoretical value (93.15%). In addition, Al/[email protected]600 exhibited excellent reusability (removal rate > 85%) after five repetitive adsorption-regeneration cycles. This study demonstrates the promising opportunities for the upcycling PET waste bottles as efficient adsorbents for the removal of emerging environmental contaminants.

Hydrothermal Synthesis of Biomass-Derived Magnetic Carbon Composites for Adsorption and Catalysis.

The synthesis of magnetic iron–carbon composites (Fe/C) from waste avocado seeds via hydrothermal carbonization (HTC) has been demonstrated for the first time. These materials are shown to be effective in adsorption and catalytic applications, with performances comparable to or higher than materials produced through conventional processing routes. Avocado seeds have been processed in high-temperature water (230 °C) at elevated pressure (30 bar at room temperature) in the presence of iron nitrate and iron sulfate, in a process mimicking natural coalification. Characterization of the synthesized material has been carried out by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES), Fourier-transform infrared spectroscopy (FT-IR), magnetometry, and through surface area measurements. The supported iron particles are observed to be predominately magnetite, with an oxidized hematite surface region. The presence of iron catalyzes the formation of an extended, ordered polymeric structure in the avocado seed-derived carbon. The magnetic Fe/C has been demonstrated as an adsorbent for environmental wastewater treatment using methylene blue and indigo carmine. Kinetic analysis suggests that the adsorbates are chemisorbed, with the positive surface charge of Fe/C being preferential for indigo carmine adsorption (49 mg g–1). Additionally, Fe/C has been evaluated as a heterogeneous catalyst for the hydroalkoxylation of phenylacetylene with ethylene glycol to 2-benzyl-1,3-dioxolane. Product yields of 45% are obtained, with 100% regioselectivity to the formed isomer. The solid catalyst has the advantages of being prepared from a waste material and of easy removal after reaction via magnetic separation. These developments provide opportunities to produce carbon-based materials for a variety of high-value applications, potentially also including energy storage and biopharmaceuticals, from a wide range of lignocellulosic biomass feedstocks.

MIL-101(Fe)-derived magnetic porous carbon as sorbent for stir bar sorptive-dispersive microextraction of sulfonamides.

Using MIL-101(Fe) as the source of carbon and Fe, a magnetic porous carbon (MPC) material with Fe3C nanoparticles encapsulated in porous carbon was prepared through one-pot pyrolysis under N2 atmosphere. With MPC as adsorption material, a stir bar sorptive-dispersive microextraction (SBSDME) method was proposed to extract and preconcentrate sulfonamides (SAs) prior to HPLC-DAD determination. To investigate their extraction ability, different MPC materials were prepared under different carbonization temperatures (600, 700, 800, 900, and 1000°C). The material prepared under 900°C (MPC-900) exhibited the highest extraction ability for SAs. The as-prepared MPC materials were also characterized by Raman spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, zeta potential, and other techniques. The main parameters that affect extraction were systematically studied. Under optimal conditions, favorable linearity (R2≥0.9938) and detection limits (0.02-0.04ngmL-1) of sulfonamides were obtained. The average recoveries for spiked milk and lake water samples ranged from 76.9 to 109% and from 75.4 to 118% with RSDs of 3.10-9.63% and 1.71-11.3%, respectively. Sulfameter and sulfisoxazole were detected in milk sample. Sulfisoxazole was detected in the lake water sample. The MPC-900 material demonstrated excellent reusability. It can be reused 24 times with peak areas having no obvious decline. The method can be applied to extract ultra-trace compounds in complex sample matrices. Schematic presentation of a stir bar sorptive-dispersive microextraction (SBSDME) by using magnetic porous carbon (MPC) composites as sorbent combined with high-performance liquid chromatography for sensitive analysis of sulfonamides in milk and lake water samples.

A sustainable strategy to fabricate porous flower-like magnetic carbon composites for enhanced microwave absorption

The design and fabrication of biomass derived flower-like Co@Co3O4/carbon (Co@Co3O4/C) composites used for high-performance microwave absorbing materials are described. The porous carbon skeleton provides the electronic pathway and the nucleation locus for Co@Co3O4 nanoparticles. Meanwhile, the porous Co@Co3O4/C composites comprising dielectric and magnetic components could also improve impedance matching and be advantageous to electromagnetic energy conversion. Labeled with good impedance matching and strong attenuation characteristics, Co@Co3O4/C composites show excellent microwave response where the minimum reflection loss (RLmin) of −46.4 dB and the maximum effective absorption bandwidth of 11.0 GHz can be achieved. This work not only explores high-performance microwave absorbing materials but also demonstrates that shrimp shell derived materials can be regarded as unexceptionably sustainable resources.

Fabrication of Ni/ZnO/C hollow microspheres decorated graphene composites towards high-efficiency electromagnetic wave absorption in the Ku-band

Developing light-weight, thin thickness and high-efficiency electromagnetic wave (EMW) absorbers is an effective strategy for dealing with the increasingly serious problem of electromagnetic radiation pollution. Herein, nickel/zinc oxide/carbon (Ni/ZnO/C) hollow microspheres decorated graphene composites were facilely prepared through the high-temperature pyrolysis of bimetallic NiZn metal-organic frameworks (MOFs) precursors. Morphological characterization results manifested that the Ni/ZnO/C microspheres with unique hollow structure were almost evenly anchored on the wrinkled surfaces of flake-like graphene. Moreover, the influences of additive amounts of graphene oxide (GO) in the MOFs precursors on the crystal structure, graphitization degree, micromorphology, magnetic properties, electromagnetic parameters and EMW absorption performance were investigated in detail. It was found that the superior EMW absorption performance could be achieved through facilely adjusting the additive amounts of GO in the precursors. As the additive amount of GO was equal to 60 mg, the obtained composite showed the comprehensive excellent EMW absorption performance. Notably, the optimal minimum reflection loss reached −57.5 dB at 16.5 GHz in the Ku-band under an ultrathin matching thickness of merely 1.34 mm, and the broadest effective absorption bandwidth achieved 5.6 GHz (from 12.4 to 18 GHz) when the thickness was 1.5 mm. Furthermore, the underlying EMW absorption mechanisms of as-prepared composites were revealed. It was believed that our results could be valuable for the structural design and EMW absorption performance modulation for MOFs derived magnetic carbon composites.

Sustainable and recoverable waste-based magnetic nanocomposites used for the removal of pharmaceuticals from wastewater

This work aimed at producing easily recoverable magnetic iron-oxide functionalized activated carbons (AC) through environmentally and energetically sustainable methods, evaluating their efficacy towards the removal of the pharmaceuticals diclofenac (DCF) and venlafaxine (VEN) from different aqueous matrices (ultrapure water and wastewater treatment plant effluents). Two AC were prepared by chemical activation of a biomassic industrial waste followed by either conventional (CP) or microwave (MW) pyrolysis. Then, magnetic iron oxide nanoparticles were loaded onto the produced AC. Differences related to the production procedure were not especially remarkable, since both the resulting magnetic composites (MAC-CP and MAC-MW) presented well-developed micropore structures with specific surface areas of 644 and 548 m2 g−1 and saturation magnetization of 32.9 and 22.5 emu g−1, respectively, which conferred them a high adsorptive performance and efficient magnetic recovery from solution. The kinetic data were well described by both pseudo-first and pseudo-second order models. As for the equilibrium data, Langmuir isotherm provided a good fitting, with maximum adsorption capacities ranging between 97 ± 2 and 215 ± 4 µmol g−1 for MAC-CP and between 80 ± 2 and 172 ± 3 µmol g−1 for MAC-MW. Additionally, in binary (DCF and VEN) solutions and wastewater, adsorption onto both MAC was somewhat inhibited due to competitive effects. MW-assisted regeneration of exhausted MAC was effective, as their adsorptive properties and chemical surface features (according to X-Ray photoelectron spectroscopy) remained unchanged. Overall, the produced waste-based magnetic carbon composites simultaneously combine high adsorptive efficiency, easy retrievability and successful regeneration/reutilization.