Magnetic Carbon Nanocomposite Research Articles

The Use of Magnetic Porous Carbon Nanocomposites for the Elimination of Organic Pollutants from Wastewater

One of the most significant challenges the world is currently facing is wastewater treatment. A substantial volume of effluents from diverse sources releases numerous pollutants into the water. Among these contaminants, organic pollutants are particularly concerning due to the associated risk of being released into the environment, garnering significant attention. Rapid advancements in agriculture and industry on a global scale generate vast volumes of hazardous organic compounds, which eventually find their way into natural systems. Recently, the release of industrial wastewater has been increasing, due to the progress of numerous businesses. This poses a danger to humans and the environment, leading to environmental contamination. The application of carbon nanocomposites in applied nanotechnology has recently expanded due to their large surface area, substantial pore volume, low preparation cost, and environmental resilience. Expanding the use of nanomaterials in water treatment is essential, as magnetic carbon nanocomposites consistently demonstrate an efficient elimination of pollutants from water solutions. In the current study, we have highlighted the application of magnetic porous carbon nanocomposites in removing organic pollutants from wastewater.

Modification of magnetic active carbon nanocomposite with SiO2 and Zincon for efficient removal of Pb(II) and 201Pb(II); multivariate optimization and adsorption characterization

This research focuses on the development of a novel surface-modified green magnetic carbon-based nanocomposite as a new adsorbent for the efficient removal of Pb(II) and 201Pb(II) from water sources. The nanocomposite was synthesized using pomegranate peel extract modification, some renewable and sustainable raw material rich in polyphenols and biologically active constituents. Then it was modified by SiO2 and Zincon for enhancement of its selectivity and performance. The prepared nanocomposite was characterized using various analytical techniques, including Fourier-transform infrared spectrophotometry (FTIR), field emission scanning electron microscopy (FESEM) coupled with energy-dispersive spectroscopy (EDS), vibrating sample magnetometer (VSM), Brunauer-Emmett-Teller (BET), and X-ray diffraction (XRD) analyses. To optimize the adsorption process, a multivariate optimization methodology based on the Box-Behnken design was employed. The optimal conditions were found to be: pH 5.4, adsorbent mass 4.0 mg, initial concentration of lead ion 54.0 mg.L-1. Adsorption isotherms and kinetic modeling studies were conducted to understand the adsorption behavior of the nanocomposite. The maximum capacity uptake was 513.5 mg.g−1. The results indicated that the surface-modified green magnetic carbon-based nanocomposite exhibited a high adsorption capacity and rapid adsorption kinetics for both Pb(II) and 201Pb(II). The pseudo-second-order kinetic model provided the best fit to the experimental data, suggesting chemisorption as the predominant adsorption mechanism. Thermodynamic analysis revealed that the adsorption process was spontaneous and exothermic, indicating the favorable nature of the adsorption.

Nanocomposites Based on Multi-Walled Carbon Nanotubes, Magnetite Nanoparticles, and Core–Shell Molecularly Imprinted Polymers in Piezoelectric Sensors for the Determination of Macrolide Antibiotics

A piezoelectric sensor with a recognition layer based on magnetic carbon nanocomposites, including multi-walled carbon nanotubes, magnetic Fe3O4 nanoparticles, and polymer nanospheres with molecular imprints of erythromycin and azithromycin, obtained by the “core–shell” method, is developed. Silicon dioxide particles are used as cores, on the surface of which a shell molecularly imprinted with macrolides is synthesized by free radical polymerization or the sol–gel method. SiO2 particles are obtained by the Stober method by varying the ratio of reagents during the synthesis. The size of the cores and nanoparticles of molecularly imprinted polymers (MIP) is determined by atomic force microscopy, and the density and uniformity of the layer on the surface of magnetic carbon nanocomposites (MCNC) are determined by the piezoelectric quartz crystal microbalance method. The optimal ratio of the reagents (template : functional monomer : cross-monomer) is established by a spectrophotometric method during the synthesis of “core–shell” nanostructures by free radical polymerization. A thin shell of SiO2 with imprints of an antibiotic based on organosilicon compounds used in the synthesis of the core is formed by the sol–gel method on the surface of the silicon dioxide core. The sensor recognition layer is formed under the action of an external magnetic field. The dependence of the analytical signal of the sensor based on MIP@SiO2/MCNC on concentration is linear in the range 5–160 µg/mL for azithromycin and 10–160 µg/mL for erythromycin, and with a recognition layer based on SiO2@SiO2/MCNC, in the concentration range 20–400 µg/mL for erythromycin.

Determination of aristolochic acid using a piezoelectric immunosensor based on magnetic carbon nanocomposites

A technique for the determination of aristolochic acid (AA) in food products using a piezoelectric immunosensor is presented. Magnetic carbon nanocomposites (MCNC) were used as the recognition layer of the sensor, on the surface of which protein conjugates of AA were immobilized. Abstract-Methods for the synthesis of Fe3O4 magnetic nuclei and their attachment to the surface of multi-walled carbon nanotubes (CNTs) have been studied. Using IR spectrometry, it was found that the formation of the recognition layer of the sensor occurs due to the formation of covalent bonds between the amino groups of AA conjugates and carboxyl groups of CNTs. The concentrations of protein conjugates based on ovalbumin (OVA) and bovine serum albumin (BSA) (0.3 and 0.2 mg/ml) and the degree of antibody dilution (0.25) were determined, which provide optimal characteristics of the piezoelectric immunosensor. The metrological characteristics of the method for determining AA have been established. The range of determined concentrations of AA and the limit of detection when using a piezoelectric immunosensor with a recognition layer based on MUNA/AA-OVA and MUNA/AA-BSA are (ng/ml): 50 – 400 and 10; 100 – 300 and 50, respectively. The sensor has been tested in the determination of AA in samples of Chinese herbal tea and dietary supplements for weight loss. No acid was found in tea, and in dietary supplements, the acid content is 3.2 μg/g.

Magnetic Carbon Nanocomposites: Preparation from Cellulose via Chemical Activation with FeCl3 and Characterization

Magnetic Carbon Nanocomposites: Preparation from Cellulose via Chemical Activation with FeCl3 and Characterization

Sodium chloride assisted synthesis of porous magnetic carbon nanocomposites containing cobalt nanoparticles for high-performance electromagnetic wave-absorption

High-performance electromagnetic wave-absorbing materials have attracted much attention owing to their wide application in military stealth, camouflage, and electromagnetic protection. Carbon materials have more advantages in achieving the performance goals of thin, light, wide, and strong absorption. The combination of ferromagnetic components is commonly used to further improve the absorption ability of carbon materials. Herein, porous Co/C nanocomposites attached with different Co content were prepared through the sodium chloride assisted carbonization process of glucose precursor containing cobalt salts. Dipole polarizations and dielectric relaxation in the carbon matrix, as well as interfacial polarizations at the heterogeneous interfaces collectively contributed to the total dielectric loss. Meanwhile, the existence of Co nanoparticles effectively improved the magnetic properties and increased magnetic loss. In addition, the impedance matching performance was also improved. As a result, the prepared Co/C nanocomposites achieved an absorption bandwidth of nearly 6 GHz, covering almost the whole Ku band from 12.1 to 18.0 GHz. And the minimum reflection loss exceeded −60 dB. This work provided a simpler and more effective approach to prepare high-performance absorbing materials.

METHODS FOR TREATING WASTEWATER FROM ORGANIC POLLUTANTS

Water pollution by organic and inorganic compounds, heavy metals, dyes, radioactive and pharmaceutical compounds has a significant impact on its use. Globalization, structural changes, economic development around the world-all this contributes to the release of pollutants that cause water pollution. That is why wastewater treatment and recovery, removing pollutants from wastewater and wastewater, is one of the most important issues. This literature review examines the problems of water pollution, its sources and types of pollutants found in water, and also discusses purification methods, including methods of water purification from pollutants, in particular phenol, in the presence of nanocomposite catalysts. Recently, more and more attention has been paid to applied nanotechnology using magnetic and carbon nanocomposites due to the advantages of production cost, high surface area, pore volume and environmental sustainability. The literature review focuses on magnetic nanocomposite catalysts based on alternating and rare earth metals with advantages such as low cost of preparation for water disinfection, high surface area, pore volume and environmental resistance. Magnetic carbon nanocomposites usually demonstrate excellent adsorption characteristics of pollutants from aqueous solutions, therefore, the expansion of the use of nanotechnology in water purification is of great importance.

Removal of Metal Ions via Adsorption Using Carbon Magnetic Nanocomposites: Optimization through Response Surface Methodology, Kinetic and Thermodynamic Studies

The toxicity of metal ions on ecosystems has led to increasing amounts of research on their removal from wastewater. This paper presents the efficient application of a carbon magnetic nanocomposite as an adsorbent for the elimination of metal ions (copper, lead and zinc) from aqueous solutions. A Box–Behnken factorial design combined with the response surface methodology was conducted to investigate the effect and interactions of three variables on the pollutant removal process. Highly significant (p < 0.001) polynomial models were developed for each metal ion: the correlation coefficient was 0.99 for Cu(II) and Pb(II), and 0.96 for Zn(II) ion removal. The experimental data were in agreement and close to the theoretical results, which supports the applicability of the method. Working at the natural pH of the solutions, with a quantity of carbon magnetic nanocomposite of 1 g/L and a metal ions’ concentration of 10 mg/L, for 240 min, removal efficiencies greater than 75% were obtained. The kinetic study indicated that a combination of kinetic models pseudo-second order and intraparticle diffusion were applied appropriately for copper, lead and zinc ion adsorption on carbon magnetic nanocomposite. The maximum adsorption capacities determined from the Langmuir isotherm model were 81.36, 83.54 and 57.11 mg/g for copper, lead and zinc ions. The average removal efficiency for five adsorption–desorption cycles was 82.21% for Cu(II), 84.50% for Pb(II) and 72.68% for Zn(II). The high adsorption capacities of metal ions, in a short time, as well as the easy separation of the nanocomposite from the solution, support the applicability of the magnetic carbon nanocomposite for wastewater treatment.

N-doped magnetic carbon nanosheets for broad, strong, stable and thin microwave absorption properties

The novel magnetic carbon nanocomposite, in which N-doped onion-like carbon encapsulated FeNi nanoparticles are embedded into N-doped carbon nanosheets, are prepared for realizing “broad, strong, stable and thin” microwave absorption behaviors. Good impedance match between magnetic FeNi nanoparticles and dielectric carbon and the large attenuation capability accompanied with strong dielectric loss ability induced by interfacial polarization loss, defect dipole polarization loss, Debye relaxation loss, conductive loss and magnetic loss originating from natural/exchange resonance and eddy current loss ensure the good microwave absorption ability. This nanocomposite exhibits the minimal reflection loss value of –27.62 dB at 4.72 GHz and the effective absorbing bandwidth of 5.76 GHz (covering 12.24–––18 GHz) at 1.9 mm and the peak of reflection loss basically locates at −21.62 dB- −27.62 dB from 1.7 mm to 5.0 mm.

Polyaniline‐co‐polyindole functionalized magnetic porous carbon derived from MIL‐53(Fe) for separation/enrichment of nitrophenols pollutants before determination with high‐performance liquid chromatography‐ultraviolet detection

Herein, a novel polyaniline-co-polyindole functionalized magnetic porous carbon derived from MIL-53(Fe) was prepared and employed as an excellent nano-adsorbent to preconcentrate trace amounts of nitro-phenols in water and wastewater samples. Briefly, magnetic MIL-53(Fe) was synthesized by the addition of magnetite nanoparticles, terephthalic acid, and FeCl3 to the reaction medium. The magnetic MIL-53(Fe) was pyrolyzed under nitrogen protection to obtain a magnetic porous carbon nanocomposite, and finally, the nanomaterial was functionalized with polyaniline-co-polyindole via oxidation polymerization. The obtained nano-adsorbent was characterized via X-ray diffraction, Fourier-transform infrared spectroscopy, vibrating sample magnetometry, and transmission and scanning electron microscopies. After that, the fabricated nano-material was utilized as an excellent nano-adsorbent for the preconcentration of trace nitro-phenols (2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol) in environmental water, and wastewater samples. The detection limits were obtained from 0.1 to 0.15μg/L after performing the optimization process. The new method was in the range of 0.4-300μg/L. The proposed method exhibited a good precision from 3.2% to 9.6% for within-day assay, and 5.2%-13.2% for between-day assay at three concentration levels (1, 50, and 250μg/L). Eventually, this method was utilized to preconcentrate/determine the target analytes in three water, and wastewater samples, satisfactory (relative standard deviations, 5.4%-9.3%; relative recovery, 88%-109%).

Super magnetic loss induced by tunable damping coefficient through Ni nanoparticles size matching in magnetic carbon

For dielectric-magnetic dual loss absorbers, magnetic loss capacity is the main contributor for improving microwave absorbing performances. Shape anisotropy induced by different morphologies and large out-of-plane anisotropy field in the material system are main common strategies to increase magnetic loss ability. We herein propose a new idea for enhancing magnetic loss capacity induced by tunable damping coefficient through Ni particle-size matching in magnetic carbon nanocomposites. As an example, for annealed magnetic carbon at 700 °C, it delivers imaginary part of permeability up to 0.462 and super magnetic loss of 0.6, resulting in minimal reflection loss of −41.91 dB at absorbing layer thickness of 3.4 mm and efficient absorbing bandwidth of 4.24 GHz at absorbing layer thickness of 2.9 mm. By applying the combination of Gilbert equation and effective medium theory, the effective permeability calculations reveals that the significant enhancement originates from the tunable damping coefficient through Ni particles size matching. The relationship model between damping coefficient and size matching has been proposed, which is well consistent with experimental data. This work is of great significance for understanding the physical process of particle size matching to strengthen electromagnetic loss ability, and provides an alternative for the design of electromagnetic absorbing materials with strong magnetic loss ability.

Pyrolyzed magnetic NiO/carbon-derived nanocomposite from a hierarchical nickel-based metal-organic framework with ultrahigh adsorption capacity

Herein, a simple one-pot solvothermal approach is used to create magnetic porous carbon nanocomposites which obtained from a nickel-based metal-organic framework (Ni-MOF) and examined for their ability to uptake methyl orange (MO) dye. Derived carbons with exceptional porosity and magnetic properties were created during the different pyrolysis temperatures of Ni-MOF (700, 800, and 900 °C) under a nitrogen atmosphere. The black powders were given the names CDM-700, CDM-800, and CDM-900 after they were obtained. A variety of analysis methods, including FESEM, EDS, XRD, FTIR, VSM, and N2 adsorption-desorption were used to characterize as-prepared powders. Furthermore, adsorbent dosage, contact time, pH variation, and initial dye concentration effects was investigated. The maximum adsorption capacities were 307.38, 5976.35, 4992.39, and 2636.54 mg/g for Ni-MOF, CDM-700, CDM-800, and CDM-900, respectively, which show the ultrahigh capacity of the resulted nanocomposites compared to newest materials. The results showed that not only the crystallinity turned but also the specific surface area was increased about four times after pyrolyzing. The results showed that the maximum adsorption capacity of MO dye for CDM-700 was obtained at adsorbent dosage of 0.083 g/L, contact time of 60 min, feed pH of 3, and temperature of 45 °C. The Langmuir model has the best match and suggests the adsorption process as a single layer. According to the results of reaction kinetic studies using well-known models, the pseudo-second-order model (R2 = 0.9989) displayed high agreement with the experimental data. The synthesized nanocomposite is introduced as a promising superadsorbent for eliminating dyes from contaminated water due to strong recycling performance up to the fifth cycle.

Magnetic carbon nanocomposites via the graphitization of glucose and their induction heating

Carbon nanocomposites containing iron-based nanoparticles are attractive materials for the catalyst supports used for magnetic (induction) heating catalysis. The metallic, soft-magnetic iron nanoparticles provide local heating of the support in an alternating magnetic field and ensure rapid magnetic separation of the nanocomposite particles from reaction suspensions. In this work, magnetic carbon nanocomposites were prepared by annealing the precursor particles consisting of iron-oxide nanoparticles dispersed in a carbohydrate matrix. The annealing was conducted at 600 °C and 750 °C in an Ar atmosphere. At both temperatures the carbothermal reduction of iron oxide to Fe/Fe3C was observed; however, at the lower temperature the rate of reduction and the growth of the nanoparticles were considerably slower. The Fe3C was formed in negligible amounts only after a prolonged period of annealing at 600 °C. A detailed structural analysis showed that the Fe/Fe3C nanoparticles catalyze the graphitization of the carbonaceous precursor material already at 600 °C, resulting in the formation of a graphitic shell that surrounds them. This shell is tight enough to prevent the areal oxidation of the encapsulated Fe nanoparticles; their magnetic properties remained unchanged even after 1 year of storage under ambient conditions. At the higher annealing temperature, the growth of the Fe/Fe3C nanoparticles caused bursting of the graphitic shell and thus partially exposed their surfaces to the atmosphere. All the nanocomposites exhibited ferromagnetic behavior in accordance with their compositions. The nanocomposite that was predominantly composed of a graphitic shell, encapsulated Fe nanoparticles and a negligible amount of Fe3C, showed the highest specific absorption rate (760 W/gFe at 274 kHz), even at a relatively low AC-field amplitude (88 mT).

Production, characteristics and use of magnetic biochar nanocomposites as sorbents

Magnetic biochar nanocomposites were obtained by in-situ co-precipitation of magnetite nanoparticles into carbon-based matrixes prepared by three different procedures: i) pyrolysis of sunflower husk (MBCSFH); ii) hydrothermal carbonization (HTC) of sunflower husk (MHCSFH) and iii) HTC of orange juice residue (MHCOR). Besides, two magnetic carbon nanocomposites were obtained in the same way using commercial activated carbon (MAC) and charcoal (MCC). All the materials were widely characterized by elemental analysis, N2 isotherms, FTIR, and Z potential and used in the sorption of malachite green (MG) from water. Kinetic fitting was done using pseudo-first-order and pseudo-second-order kinetic models, where it was found that experimental data fitted well with the second-order kinetic model. MHCSFH and MHCOR exhibited the maximum removal efficiencies (77.00% and 82.18%) compared to their corresponding carbon precursors (63.32% and 34.29%). The post-sorption characterization of MHCOR indicates electrostatic interactions, electron sharing, and п-п interactions and pore filling are the principal interactions between sorbent and MG. In addition to the synthesis and characterization of magnetic biochar nanocomposites, this research demonstrated the capacity of sorbents materials for pollutants removal.

Magnetic porous carbon nanocomposites derived from cactus (Opuntia stricta Haw.) for the removal of toxic dyes: optimization of synthesis conditions using response surface methodology

AbstractBACKGROUNDWater purification of industrial effluents containing toxic organic dyes by low‐cost biomass‐based adsorbents is not only in accordance with environmental remediation policies, but also reduces total treatment costs. The conversion of Opuntia stricta Haw. biowaste, one of the most harmful invasive plants, into absorbents can lessen the ecological problems caused by this plant species as well as create more value‐added products for water decontamination. We report on the fabrication conditions of O. stricta zinc ferrite (ZnFe2O4)‐loaded activated carbon (ZnFe2O4@AC) for the elimination of two types of dyes including Rhodamine B (RhB), methyl orange (MO) and acid yellow17 (AY), with process optimization based on response surface methodology combined with Box–Behnken design. The optimized ZnFe2O4@AC was structurally characterized by scanning electron microscopy and X‐ray diffraction.RESULTSThe optimal ZnFe2O4@AC was attained at a 1.5 ZnFe2O4:OBC ratio, 5 h carbonization time and 519 °C pyrolysis temperature. In removing RhB, MO and AY by optimized ZnFe2O4@AC, remarkable adsorption capacities (53.34–82.8 mg g−1) were achieved via confirmation tests with very low errors (<2%) and high desirability (>95%). Moreover, kinetic results suggested that the Elovich model was the best description for RhB and AY dye adsorption, whereas MO adsorption by ZnFe2O4@AC followed the pseudo‐second‐order model. The maximum adsorption capacities calculated from the Langmuir equation were determined in the order: AY (82.73 mg g−1) < RhB (125.13 mg g−1) < MO (180.51 mg g−1).CONCLUSIONZnFe2O4@AC derived from O. stricta could be recommended as a high‐efficiency bioadsorbent for the elimination of cationic, anionic and neutral dyes. © 2022 Society of Chemical Industry (SCI).

Separation of organic pesticide (insecticide): lambda-cyhalothrin from wastewater using magnetic carbon nanocomposites

Separation of organic pesticide (insecticide): lambda-cyhalothrin from wastewater using magnetic carbon nanocomposites

One-step in-situ sustainable synthesis of magnetic carbon nanocomposite from corn comb (MCCC): agricultural biomass valorisation for pollutant abatement in wastewater.

This study explored a novel, eco-friendly, sustainable, low-cost, and abundantly available corn comb (CC) agricultural biomass waste-derived one-step in-situ synthesis of magnetic carbon (MCCC) as an efficient adsorbent for water decontamination applications. Herein, we developed a robust and easily separable MCCC by carbonization of Fe(NO3)3.9H2O single iron salt-soaked CC at 500°C for 5h. The as-synthesized MCCC was confirmed for their physicochemical properties by various characterization techniques viz. scanning electron microscopy (SEM), high-resolution transmission emission microscopy (HR-TEM), energy dispersive X-ray (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), surface area measurements by Brunauer-Emmett-Teller (BET) study, Raman analysis, and magnetic behavior by VSM analysis. The adsorption properties of MCCC on prototypical pollutant methylene blue (MB) was monitored depending on the effect of pH, adsorbent dose, contact time, and varying concentrations of MB. Especially, the π-π interactions played important role in the adsorption of MB at acidic pH (pH = 4). The MCCC displayed a maximum uptake capacity of 120.73 ± 0.63 mg/g toward MB. The Langmuir, Freundlich, and Temkin adsorption isotherm models were fitted with determined coefficient (R2) values of 0.99, 0.95, and 0.96 respectively. The kinetics of the adsorption process was well fitted with a pseudo-second-order model (R2 = 0.99). Most significantly, the as-designed easily separable, and reusable adsorbent, MCCC was effectively applied for the abatement of pollutants, different kinds of dyes, pesticides, and industrial wastewater samples. The sustainable, affordable, and waste to wealth-based MCCC with a simple synthesis methodology can be fruitfully applicable for environmental remediation and water decontamination.

Using silk-derived magnetic carbon nanocomposites as highly efficient Nanozymes and electromagnetic absorbing agents

Using silk-derived magnetic carbon nanocomposites as highly efficient Nanozymes and electromagnetic absorbing agents

Magnetic Fe/Fe3C@C Nanoadsorbents for Efficient Cr (VI) Removal

Magnetic carbon nanocomposites (α-Fe/Fe3C@C) synthesized employing fructose and Fe3O4 magnetite nanoparticles as the carbon and iron precursors, respectively, are analyzed and applied for the removal of Cr (VI). Initial citric acid-coated magnetite nanoparticles, obtained through the co-precipitation method, were mixed with fructose (weight ratio 1:2) and thermally treated at different annealing temperatures (Tann = 400, 600, 800, and 1000 °C). The thermal decomposition of the carbon matrix and the Fe3O4 reduction was followed by thermogravimetry (TGA) and Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, Raman spectroscopy, SQUID magnetometry, and N2 adsorption-desorption isotherms. A high annealing temperature (Tann = 800 °C) leads to optimum magnetic adsorbents (high magnetization enabling the magnetic separation of the adsorbent from the aqueous media and large specific surface area to enhance the pollutant adsorption process). Cr (VI) adsorption tests, performed under weak acid environments (pH = 6) and low pollutant concentrations (1 mg/L), confirm the Cr removal ability and reusability after consecutive adsorption cycles. Physical adsorption (pseudo-first-order kinetics model) and multilayer adsorption (Freundlich isotherm model) characterize the Cr (VI) absorption phenomena and support the enhanced adsorption capability of the synthesized nanostructures.

Influence of post-pyrolysis treatment on physicochemical properties and acid medium stability of magnetic carbon nanocomposites

AbstractThis study presents the preparation of magnetic carbon nanocomposites (MCNCs) through a two-step procedure: (i) in situ co-precipitation of magnetite (Fe3O4) nanoparticles into four different carbonaceous matrixes and (ii) post-pyrolysis treatment to coat the magnetic core. Four post-pyrolysis MCNCs were obtained: MACP (post-pyrolyzed magnetic activated carbon), MCCP (post-pyrolyzed magnetic charcoal), MHCPOR(post-pyrolyzed magnetic hydrochar from orange residue), and MBCPSFH(post-pyrolyzed magnetic biochar from sunflower husk). These four samples were compared with the starting MCNCs prepared without post-pyrolysis treatment: MAC, MCC, MHCOR, and MBCSFH, respectively. After post-pyrolysis treatment, a thin carbon layer surrounding some of the magnetite nanoparticles was identified by transmission electron microscopy. Post-pyrolysis modified the porous structure and chemical composition of MCNCs. Furthermore, a leaching test with acid sulfuric solution at 90 °C was carried out. The results suggested that the MHCPORand MBCPSFHwere more stable in an acidic medium than MACP and MCCP, indicating that the coat generated during post-pyrolysis of hydrochar and biochar could partially protect the magnetic core by reducing Fe leaching into the aqueous solution. Biochar and the hydrochar-based MCNCs before and after post-pyrolysis treatment exhibit superparamagnetic properties; however, their saturation magnetization (Ms) decreased considerably. These results open the potential application fields of MCNCs obtained by post-pyrolysis of biochar and hydrochar-based materials in acidic mediums.