Cobalt Ferrite Nanocomposites Research Articles

A novel, sensitive and selective nanosensor based on graphene nanoribbon–cobalt ferrite nanocomposite and 1-methyl-3-butylimidazolium bromide for detection of vanillin in real food samples

A novel, sensitive and selective nanosensor based on graphene nanoribbon–cobalt ferrite nanocomposite and 1-methyl-3-butylimidazolium bromide for detection of vanillin in real food samples

A Facile Synthesis of Bi2O3/CoFe2O4 Nanocomposite with Improved Synergistic Photocatalytic Potential for Dye Degradation

Semiconductor-based photocatalysis is a probable approach to overcoming many pollution problems and eradicating toxic organic materials from wastewater. This research endeavor aimed to explore the synergistic potential of different semiconductor nanocomposites for photocatalytic degradation of organic pollutants in contaminated water. A facile hydrothermal approach was employed to synthesize bismuth oxide and cobalt ferrite nanoparticles from their precursors—bismuth nitrate pentahydrate, ferric chloride hexahydrate and cobalt chloride hexahydrate—with various concentrations and conditions to optimize the product. Subsequently, nanocomposites of bismuth oxide and cobalt ferrite were prepared by solid-state mixing in varying concentrations followed by calcination. UV/visible diffuse reflectance spectroscopy, X-ray diffraction, scanning electron microscopy and elemental dispersive X-ray spectroscopic techniques have corroborated the successful synthesis of nanocomposites. The energy gaps of bismuth oxide and cobalt ferrite nanocomposites were computed in the range of 1.58–1.62 eV by Tauc plots. These nanocomposite materials were ascertained for photocatalytic potential to degrade methyl orange organic dye in water. A nanocomposite with equiquantic proportions has shown the best photocatalytic degradation activity, which may be attributed to the type-II band configuration and a synergistic effect, because Bi2O3 acts as an electron sink. This synergism has reduced the cogent band gap, hindered electron hole recombination and increased electron hole availabilities for photodegradation reactions, thus ensuing an efficient photodegradation co-work of Bi2O3/CoFe2O4 nanocomposites.

Effect of Graphene Concentration on the Electrochemical Properties of Cobalt Ferrite Nanocomposite Materials.

A two-step process was applied to synthesize the cobalt ferrite-graphene composite materials in a one-pot hydrothermal reaction process. Graphene Oxide (GO) was synthesized by a modified Hummer’s method. The synthesized composite materials were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). The XRD and FTIR results were in good agreement with the TGA/DTG observations. SEM and TEM disclosed the spherical shape of the nanoparticles in 4–10 nm. The optimized CoFe2O4-G (1–5 wt.%) composite materials samples were tried for their conductivity, supercapacity, and corrosion properties. The CV results demonstrated a distinctive behavior of the supercapacitor, while the modified CoFe2O4-G (5 wt.%) electrode demonstrated a strong reduction in the Rct value (~94 Ω). The highest corrosion current density valves and corrosion rates were attained in the CoFe2O4-G (5 wt.%) composite materials as 5.53 and 0.20, respectively. The high conductivity of graphene that initiated the poor corrosion rate of the CoFe2O4-graphene composite materials could be accredited to the high conductivity and reactivity.

Bisphenol A degradation by peroxymonosulfate photo-activation coupled with carbon-based cobalt ferrite nanocomposite: Performance, upgrading synergy and mechanistic pathway

Cobalt ferrite (CoFe2O4, CF) nanoparticles were anchored on the multiwalled carbon nanotube (MWCNT) for synthesis of CF@MWCNT nanocomposite and enhancing the catalytic activity of CF. After well characterization, it was applied as a catalyst towards photo-activation peroxymonosulfate (PMS) for degradation of bisphenol A (BPA). Based on the identified intermediates, a possible degradation pathway was proposed for BPA. CF@MWCNT coupled with PMS and UV (i.e., CF@MWCNT/PMS/UV) exhibited a better performance than homogeneous UV-assisted PMS processes under Fe and Co ions. A significant synergy on the degradation of BPA was observed in the simultaneous application of catalyst, UV light and PMS. Under optimum conditions, the removal efficiencies of 100 and 72.6% were attained respectively for BPA and TOC by CF@MWCNT/PMS/UV within 60 min reaction. These efficiencies were decreased to 88 and 61% after five times use of catalyst, respectively. The leaching of metal ions dissolved from the catalyst was slight during cyclic utilization of catalyst, confirming high stability of CF@MWCNT. In this process, the participation of radical mechanisms was approximately 60%, which SO4•– and HO• species contributed as predominant oxidizing reactive species. It also showed the excellent catalytic performance towards decomposition of persulfate and hydrogen peroxide. Overall, UV-assisted PMS catalyzed by CF@MWCNT exhibited a good catalytic performance and so it can be potentially introduced as a promising method for efficient treatment of water contaminated by BPA.

Observation of Room‐Temperature Low‐Field Magnetoresistance in Reduced Graphene Oxide/CoFe2O4 Nanocomposites

The considerable spin diffusion length and high electron mobility of graphene at room temperature makes it a suitable candidate to improve the spin transport properties of magnetic semiconductors when incorporated in a suitable stoichiometry. Herein, an observation of room‐temperature magnetoresistance (MR) properties of reduced graphene oxide (rGO)/cobalt ferrite (CFO) nanocomposites, which are synthesized by chemical methods followed by mixing in different mass ratios, is reported. The magnetic field‐dependent electrical resistivity shows a decrease in resistivity with the increase in magnetic field from 0 to 0.5 T, representing a negative MR in our samples. The highest MR of around −1.4% is observed in the 1:1 ratio CFO and rGO nanocomposite, whereas the samples with 2:1 and 3:1 ratio show the MR of ≈−1%. In the CFO–rGO nanocomposite, the charge transport takes place mainly through the rGO layers due to the insulating nature of the CFO nanoparticles. However, the ferromagnetic moments of the CFO nanoparticles induce electron‐spin scattering during the charge transport. The reduction in electron‐spin scattering results due to the parallel alignment of the magnetic moments. The alignment of ferromagnetic moments under the external magnetic field has been further confirmed from the magnetocapacitance effect of CFO nanoparticles.

Green synthesis of reduced graphene oxide-CoFe2O4 nanocomposite as a highly efficient visible-light-driven catalyst in photocatalysis and photo Fenton-like reaction

In this study, reduced graphene oxide (rGO)-cobalt ferrite (CoFe2O4) nanocomposite was synthesized by green mechano-thermal methods. The synthesized material was characterized using XRD, FTIR, SEM, TGA, UV–vis, VSM, and XPS. The as-prepared rGO-CoFe2O4 with a suitable band gap of 1.89 eV was explored as a photoactive material in visible-light degradation of two basic dyes namely, basic red 46 (BR46) and basic red 18 (BR18). In photocatalysis, BR46 and BR18 were degraded up to 76 and 79%, with apparent rate constants of 0.0051 and 0.0045 min−1, respectively. In the photo Fenton-like reaction, the efficiency and the rate constant were enhanced compared to photocatalysis and found to be 88% and 0.0088 min−1 for BR46 and 90% and 0.0093 min−1 for BR18. The hydroxyl radicals were the main active species responsible in the visible/rGO-CoFe2O4/H2O2 system. The in vitro study on human umbilical vein endothelial cells (HUVEC) suggested the non-cytotoxicity of as-prepared nanocomposite.

Magnetic properties and kinetic roughening study of prepared polyaniline: lead ferrite, cobalt ferrite and nickel ferrite nanocomposites electrodeposited thin films

The purpose of this study is preparation of polyaniline–lead ferrite, polyaniline–cobalt ferrite and polyaniline/nickel ferrite thin layers. The electromagnetic pollution is a serious problem in the world that can be solved by electromagnetic interference (EMI) shielding. The EMI layers can be synthesized by conductive layer composed by magnetic particles. Crystallite size of samples was studied by (XRD) analyze via Debye–Scherrer and Williamson–Hall equations. The X-ray diffraction XRD patterns confirm the crystalline structure of the samples. The surface morphology of the composite layers was investigated by scanning electron microscopy (SEM) and the effect of thickness and different composed particles was investigated. The percentage of the constituents and purity of samples was studied by energy dispersive X-ray analysis (EDX) analysis. Also, surface roughness and kinetic roughening of thin films was investigated using atomic force microscopy (AFM). Hysteresis loop of the magnetic samples were analyzed by vibrating sample magnetometer (VSM). These new easy prepared nanocomposites introduce a suitable and effective coating for electromagnetic interference (EMI) shielding.

Review on Recent Advances of Synthesis, Magnetic Properties, and Water Treatment Applications of Cobalt Ferrite Nanoparticles and Nanocomposites

Nowadays, CoFe2O4 (cobalt ferrite) nanoparticles have fascinated numerous researcher’s consideration because of their latent implementation in water treatment. CoFe2O4 nanoparticles are cost-efficient magnetic materials and are stable under diverse environments. Therefore, they are effortlessly removed from purified water by means of an external magnetic field and reclaimed for quite a lot of cycles. In this analysis, the focus was given on learning the influences of some aspects including calcination temperature, crystalline size, pH, synthesis method, and dopant type on the magnetic properties of CoFe2O4 nanocomposites and nanoparticles. The implementation of CoFe2O4 nanoparticles in water purification and its capability to be united with various nanoparticles for adsorption and photocatalysis were entirely conferred. The chance of retrieval and reprocess of CoFe2O4 nanoparticles and its nanocomposites were discussed. Finally, the holes which are still not built up for study in the modification of physical properties and further magnetic properties of CoFe2O4 nanoparticles for its complete usage in water treatment were delineated. Henceforth, using CoFe2O4 nanoparticles and its nanocomposites at trade scale for water treatment will definitely reduce the expenses of water as it uses visible light as the energy source and because of its capability to be recycled numerous times.

The photocatalytic performance and structural characteristics of nickel cobalt ferrite nanocomposites after doping with bismuth

Here, a novel bismuth-doped nickel-cobalt ferrite (Ni0.5Co0.5Bi0.1Fe1.9O4) was synthesized using a sol-gel auto-combustion approach. The impact of bismuth substitution on the nickel-cobalt ferrite structural characteristics was investigated relative to the nickel-cobalt ferrite without bismuth substitution (Ni0.5Co0.5Fe2O4) based on diverse technical options (e.g., scanning electron microscopy-equipped with an energy dispersive X-ray spectrometer, X-ray diffraction, physisorption, and Fourier-transform infrared spectroscopy). Bismuth doping increased the surface area without affecting pore size. The X-ray diffraction pattern confirmed a nano-ferrite cubic spinel structure of the catalyst. Photodegradation of Congo red (CR) was tested using these nickel-cobalt ferrite catalysts under visible light across varying reaction parameters (e.g., pH, catalyst loading, dye concentration, and reaction time). The photo-degradation efficiency for CR in aqueous medium was the highest (98%) at pH 3 with 0.2 g catalyst loading in 100 mL under visible irradiation to reinforce the role of nanostructures as a potent photocatalyst (QY = 2.79 × 10−7 molecule photon−1). The kinetic reaction rate of Bi-doped spinel ferrite (3.5 µmol g−1 h−1) was1.25 times higher than those undoped materials. This study experimentally proved that the bismuth-doped nickel-cobalt ferrite photocatalyst is an effective option for removing industrial dyes.

Polymer-wrapped reduced graphene oxide/nickel cobalt ferrite nanocomposites as tertiary hybrid supercapacitors: insights from experiment and simulation

The tertiary hybrid supercapacitor consisting of PEDOT:PSS wrapped reduced graphene oxide/Ni 0.5 Co 0.5 Fe 2 O 4 (PGNC) was developed and its supercapacitance performance has been compared with that of the reduced graphene oxide (rGO)/Ni 0.5 Co 0.5 Fe 2 O 4 (GNC), carbon nanotube (CNT)/Ni 0.5 Co 0.5 Fe 2 O 4 (CNC) and carbon nanotube/reduced graphene oxide/Ni 0.5 Co 0.5 Fe 2 O 4 (CGNC). Among all, PGNC exhibits an excellent specific capacitance of 1286 Fg −1 with a capacitance retention of 95% over 6000 cycles at a current density of 0.5 Ag −1 . The synergetic effects between rGO, Ni 0.5 Co 0.5 Fe 2 O 4 and the PEDOT:PSS polymer result in an increase in the specific surface area and the pore volume, making PGNC an excellent hybrid supercapacitor for energy storage. The enhancement in the specific capacitance of the PGNC nanocomposite is further validated through first-principles density functional theory calculations, which predict an increment in the density of states at the Fermi level of the GNC and CNC nanocomposites compared to the isolated Ni 0.5 Co 0.5 Fe 2 O 4 material. The supercapacitance performance of the PGNC nanocomposite is reported for different electrolytes, different stoichiometric ratios of Ni and Co in Ni x Co 1-x Fe 2 O 4 and on different substrates. • PGNC hybrid supercapacitor showed more specific capacitance than other supercapacitors. • The enhanced density of states and specific surface area reveals the more specific capacitance of PGNC. • The increase in specific surface area of PGNC was further corroborated by positron annihilation studies. • The effect of electrolyte and substrate on specific capacitance of PGNC was also studied.

Structural, fabrication and enhanced electromagnetic wave absorption properties of reduced graphene oxide (rGO)/zirconium substituted cobalt ferrite (Co0·5Zr0·5Fe2O4) nanocomposites

In this work, zirconium (Zr) substituted cobalt ferrite, Co0·5Zr0·5Fe2O4 (CoZrFe) and its composite with reduced graphene oxide (rGO) were synthesized by a two-step process. The structural and surface analysis of the composites were investigated by powder XRD, Raman analysis, TEM, and XPS. The magnetic properties of rGO/Co0·5Zr0·5Fe2O4 (rGO-CoZrFe) nanocomposites (NCs) were also studied by using VSM analysis. The rGO-CoZrFe NCs results showed that the Zr doped CoFe2O4 NPs were formed and uniformly wrapped on the surfaces of rGO. Microwave adsorption studies of rGO-CoZrFe NCs were performed using a vector network analyzer in 2–18 GHz frequency range. Minimum Reflection Loss (RL) of the prepared rGO-CoZrFe NCs were reached −31.89 dB at 4.2 GHz frequency range for the thickness of 5 mm pellet, the effective absorption bandwidth (RL less than −10 dB) is up to 4.0 GHz with very small thickness of 1 mm. This result indicates that these novel rGO-CoZrFe NCs will be potential candidates for efficient material in the electromagnetic wave adsorption filed.

Effect of heat treatment on the microstructural properties of silica embedded cobalt ferrite nanocomposites

Silica coated cobalt ferrite (CoFe2O4:SiO2) nanocomposites were synthesized by co-precipitation technique using metal nitrates as precursors. The as-prepared samples were heat treated at different temperatures of 250, 500 and 750 °C for 24 h. Structural, thermal, and morphological behavior of nanocomposites are investigated by XRD, FTIR, TGA-DTG, and SEM characterization results, useful in biomedical applications. With increasing calcinations temperature from 250 to 500 °C and 750 °C an increase in crystallite size of CoFe2O4:SiO2 nanocomposites has been determined from 20.26 to 28.95 nm and 38.76 nm by Williamson–Hall method, respectively. Furthermore, by increasing the temperature from 250 to 750 °C the lattice parameter and strain values have been found to increase from 8.0321 to 8.0691 Å and 1.01 × 10−2 to 3.75 × 10−3, respectively. Analysis of TGA results found no weight loss when the sample was heated beyond 700 °C and thus complete decomposition of precursors has led to the formation of stable nanocomposite structures at high temperatures. SEM analysis of synthesized samples at 750 °C revealed well developed nanoparticles of CoFe2O4: SiO2 with inter-granular porosity.

Dynamic modelling of Alginate - Cobalt ferrite nanocomposite for removal of binary dyes from textile effluent

The performance of Alginate - Cobalt ferrite (ACF) in a fixed bed column was assessed for the simultaneous removal of binary dyes from textile effluent. The binary dye effluent containing 32.5 mg/L of reactive red 195 (RR195) and 21 mg/L of reactive yellow 145 (RY145) was used for the study. The effect of various parameters like bed depth (3, 6, 9 and 12 cm) and flow rate of influent (5, 7.5 and 10 mL/min) for the binary adsorption using ACF was studied. The results revealed that ACF bed capacity and maximum adsorption capacity showed an increasing trend with an increased bed depth and decreased flow rate. Dynamic modeling such as Yoon - Nelson model, Thomas model and Bed Depth Service Time model (BDST) were evaluated with the experimental data. Comparatively, Yoon - Nelson and Thomas model presented better fitness for the elimination of RR195 and RY145 dye. The experimental data from dynamic studies revealed ACF's effectiveness for the sequestration of binary dyes from textile effluent.

Structural, ferromagnetic, electrical, and dielectric relaxor properties of BaTiO3 and CoFe2O4 bulk, nanoparticles, and nanocomposites materials for electronic devices

Barium titanate (BaTiO3, BTO) and cobalt ferrite (CoFe2O4, CFO) nanoparticles, bulk, and nanocomposites samples were synthesized at optimized parameters using the chemical route. Structural studies revealed that all the samples showed a single-phase structure. The value of activation energy in the case of nanocomposites was 975 meV, while it was 1.58 eV and 1.0 eV for BTO and CFO-nanoparticles, respectively. We observed that the saturation magnetization and remanence of the CFO-nano sample were three times greater than the 0.3CFO–0.7BTO nanocomposite. At 10 kHz, the dielectric constants are measured 4500 (BTO-bulk), 1550 (BTO-nano), 820 (CFO-bulk), 275 (CFO-nano), and 375 (BTO–CFO nanocomposites) for a various sample of series. We found at 10 kHz, the transition from ferroelectric to paraelectric in the case of BTO-nano (Tc = 363 °C) and CFO-nano (Tc = 212 °C), while nanocomposite BTO–CFO initial change phases from ferroelectric to anti-ferroelectric (relaxor behavior) at Td = 312 °C and then from anti-ferroelectric to paraelectric (Tm > 400 °C). Similarly, in the case of CFO-bulk, we noticed Tm = 204 °C (ferroelectric to anti-ferroelectric) and Tm = 314 °C (anti-ferroelectric to paraelectric). Overall, we concluded from these studies and data that nanocomposite 0.7BaTiO3–0.3CoFe2O4 and CFO-bulk sample showed relaxor behavior as well along with the transformation change from ferroelectric to paraelectric. While BTO-nano and CFO-nano and BTO-bulk showed their transformation direct from ferroelectric to paraelectric. These simultaneous ferromagnetic and ferroelectric (dielectric) measurements confirmed the presence of multiferroic properties in our nanocomposite as well as CFO-nano and CFO-bulk systems. These proposed materials may be useful for ferroelectric and data storage devices.

Fabrication of magnetic cobalt ferrite nanocomposites: an advanced method of removal of toxic dichromate ions from electroplating wastewater

Magnetic cobalt ferrites (CoFe2O4) were synthesized by sol-gel method. These nanoparticles were ultra-sonicated with surface modified multi-walled carbon nanotubes (SM-MWCNTs) to form CoFe2O4/SM-MWCNTs nanocomposites. The as-prepared materials were used as an adsorbent for the removal of hexavalent chromium (Cr(VI)) arising from the presence of dichromate ions (Cr2O72− ) in the electroplating effluent. The synthesized nanocomposites were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-Ray diffraction (XRD), Fourier transmission infrared spectroscopy (FT-IR), raman spectroscopy, thermo-gravimetric analysis (TGA), and zeta analyzer. The effect of the environmental chemistry of the solution on the adsorption has been discussed. The adsorption isotherm of Cr(VI) adsorption onto the as-synthesized CoFe2O4/SM-MWCNTs best fitted the Langmuir Adsorption Isotherm model. The high adsorption capacity of 100mg/g was achieved at 40°C under optimized conditions. Besides, the magnetic properties of synthesized CoFe2O4/SM-MWCNTs nanocomposites allow them to separate from the aqueous solution by magnetization easily. Even after seven consecutive adsorption-desorption cycles, the CoFe2O4/SM-MWCNTs nanocomposites presented an efficiency loss of less than 20% for the removal of Cr(VI) ions. This study clearly shows that cobalt nanocomposites are promising candidates in environmental applications.

Faujasite zeolite decorated with cobalt ferrite nanoparticles for improving removal and reuse in Pb2+ ions adsorption

Water pollution caused by heavy metals ions has been gaining attention in recent years, increasing the interest in the development of methodologies for their efficient removal focusing on the adsorption process for these purposes. The current challenge faced by adsorption processes is the adequate adsorbent immobilization for removal and reuse. Thus, the present work aimed at producing a faujasite zeolite nanocomposite decorated with cobalt ferrite nanoparticles for Pb2+ ions adsorption in an aqueous medium improving magnetic removal and reuse. As a result, a high surface area (434.4 m2·g−1) for the nanocomposite and an 18.93 emu·g−1 saturation magnetization value were obtained, indicating magnetic removal in a promising material for adsorption process. The nanocomposite regeneration capacity evaluated by magnetic recovery after 24 h suspension presented a high Pb2+ ion adsorptive capacity (98.4%) in the first cycle. Around 98% of the Pb2+ ions were adsorbed in the second cycle. In this way, the synthesized faujasite:cobalt ferrite nanocomposite reveals itself as a promising alternative in adsorption processes, aiming at a synergic effect of FAU zeolite high adsorptive activity and the cobalt ferrite nanoparticles magnetic activity, allowing for adsorbent recovery from the aqueous medium via magnetic force and successive adsorptive cycles.

La(OH)3-modified magnetic CoFe2O4 nanocomposites: A novel adsorbent with highly efficient activity and reusability for phosphate removal

Eutrophication of water bodies caused by excessive phosphate discharge has become a serious environmental issue. In order to develop a easily separable adsorbent to effectively remove phosphate from water, La(OH)3-modified magnetic cobalt ferrite (CoFe2O4) nanocomposites (Lax-CF) were synthesized by coprecipitation assisted hydrothermal method. The La2-CF with the mass ratio of La(OH)3 to CoFe2O4 of 2:1 exhibited the largest adsorption capacity of 104.01 mg P/g and prominent magnetic properties. Batch experiments showed that pseudo second-order model and Langmuir model matched well adsorption kinetic and isotherm, respectively. Moreover, the excellent adsorption performance of La2-CF can be attributed to the following mechanism: (i) protonated and positively charged adsorbent adsorbed the phosphate by electrostatic attraction; (ii) the ligand exchange between the hydroxyl group and the phosphate resulted in the formation of an inner sphere complex, thereby enhancing the adsorption capacity for phosphate. It was worth noting that La2-CF exhibited high stability and optimal adsorption selectivity to phosphate when the competitive anions were added with the pH in the range of 3.0–9.0. Besides, the adsorption efficiency decreased slightly and remained above 80% after 6 cycles, suggesting excellent reusability of this adsorbent. This work provided a remarkable reference for the research of phosphate adsorption materials with high selectivity and stability.

Chitosan supported CoFe2O4 for the removal of anthraquinone dyes: kinetics, equilibrium and thermodynamics studies

Chitosan supported cobalt ferrite nanocomposite (Cs–CoFe2O4) was synthesized and characterized. The synthesized Cs–CoFe2O4 was used for the removal of Anthraquinone dyes (Methylene Green, MG and Reactive blue 4, RB4) from aqueous solution in batch processes. Kinetics data were subjected to pseudo-first-order and pseudo-second-order, Elovich and intra-particle diffusion models, while the equilibrium data were evaluated with Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The results of characterizations revealed that CoFe2O4 was successfully incorporated into the Cs, with resulting composite retaining its magnetic properties and the functional group in the Cs. Considering the closeness Qe(exp) and Qe(cal.), also the values of R2 and %SSE, the MG adsorption followed pseudo-second-order with average rate constants of 8.3 × 10−3 min−1 while the adsorption kinetic of RB4 is best described by pseudo-first-order model with average rate constant of 2.91 × 10−2 min−1. Langmuir adsorption isotherm fits gave R2 > 0.9 for both dyes with maximum adsorption capacities of 63.34 and 35.05 mg/g obtained MG and RB4 respectively. The thermodynamic parameters showed revealed spontaneous adsorption processes. The results indicated that the prepared Cs–CoFe2O4 is an efficient recyclable adsorbent for the MG and RB4 dye without losing the original activity and stability for water treatment applications.

Synthesis and Characterization of CoFe2O4/MWCNTs Nanocomposites and High-Frequency Analysis of Their Dielectric Properties

Nanoparticles of CoFe2O4 were synthesized by chemical co-precipitation method. The CoFe2O4/MWCNT nanocomposites were synthesized with increasing contents of MWCNTs, i.e., 0.0, 2.0, 3.0, and 5.0% by weight via ultrasonication method in a dispersive medium using ortho-xylene. The synthesized cobalt ferrite nanoparticles and their nanocomposites were characterized by impedance analyzer, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and x-ray diffraction (XRD) techniques. The XRD indexed patterns confirmed the face-centered cubic structure of CoFe2O4/MWCNT nanocomposites. The average crystallite size in all the samples was in the range of 15 to 35 nm. The decorations of CoFe2O4 on MWCNTs were confirmed by SEM images. The FTIR results showed two vibrational bands. With the increasing contents of multi-walled carbon nanotubes in the cobalt ferrite/MWCNT nanocomposites, the dielectric properties were also enhanced. At 1 MHz, dielectric constant, dielectric loss, and tangent loss factor were increased from 26, 15.1, and 0.580 for pure cobalt ferrite to 47, 28.9, and 0.614 for loading of 5% MWCNTs, respectively. At 1 GHz, dielectric constant, dielectric loss, and tangent loss factor were increased from 11.6, 0.33, and 0.028 for pure cobalt ferrite to 19.4, 0.61, and 0.031 for loading of 5% MWCNTs, respectively. Such a huge increase in the dielectric properties of cobalt ferrite and multi-walled carbon nanocomposites exploited their applications at high frequency.

MIL-101(Cr)-cobalt ferrite magnetic nanocomposite: synthesis, characterization and applications for the sonocatalytic degradation of organic dye pollutants.

In this study, for the first time, a novel magnetically recyclable MIL-101(Cr)/CoFe2O4 nanocomposite was prepared via a facile solvothermal method. The morphology, structural, magnetic and optical properties of the nanocomposite were characterized via field emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), UV-visible spectroscopy (UV-visible) and BET surface area analysis. Furthermore, the sonocatalytic activity of the MIL-101(Cr)-based magnetic nanocomposite was explored for the degradation of organic dye pollutants such as Rhodamine B (RhB) and methyl orange (MO) under ultrasound irradiation in the presence of H2O2. Under optimized conditions, the degradation efficiency reached 96% for RhB and 88% for MO. The sonocatalytic activity of MIL-101(Cr)/CoFe2O4 was almost 12 and 4 times higher than that of the raw MIL-101(Cr) and pure CoFe2O4, respectively. The improved sonocatalytic performance of the as-prepared binary nanocomposite can be attributed to the relatively high specific surface area of MIL-101(Cr) and magnetic property of CoFe2O4, as well as the fast generation and separation of charge carriers (electrons and holes) in MIL-101(Cr) and CoFe2O4. In addition, the trapping tests demonstrated that ·OH radicals are the main active species in the dye degradation process. Moreover, the most influencing factors on the sonocatalytic activity such as the H2O2 amount, initial dye concentration and catalyst dosage were investigated. Finally, the nanocomposite was magnetically separated and reused without any observable change in its structure and performance even after four consecutive runs.