Characterization of cobalt ferrite-supported activated carbon for removal of chromium and lead ions from tannery wastewater via adsorption equilibrium

In this experiment,cobalt ferrite-supported activated carbon(CF-AC)was developed and characterized via the wet impregnation method for the removal of Cr and Pb(II)ions from tannery wastewater.Batch adsorption was carried out to evaluate the effect of experimental operating conditions(pH of solution,contact time,adsorbent dose,and temperature),and the removal efficiencies of Cr and Pb(II)ions by the developed adsorbents were calculated and recorded for all experimental conditions.These variables were estimated and reported as removal efficiencies of 98.2%for Cr and 96.4%for Pb(II)ions at the optimal conditions of 5,0.8 g,80 min,and 333 K for pH,adsorbent dose,contact time,and temperature,respectively.The equilibrium for the sorption of Cr and Pb(II)ions was studied using four widely used isotherm models(the Langmuir,Freundlich,Dubinin-Radushkevich,and Temkin isotherm models).It was found that the Freundlich isotherm model fit better with the coefficient of determination(R2)of 0.9484 and a small sum of square error of 0.0006.The maximum adsorption capacities(Qm)of Pb(II)and Cr adsorbed onto CF-AC were determined to be 6.27 and 23.6 mg/g,respectively.The adsorption process conformed well to pseudo-second order kinetics as revealed by the high R2 values obtained for both metals.The thermodynamic parameters showed that adsorption of Cr and Pb(II)ions onto CF-AC was spontaneous,feasible,and endothermic under the studied conditions.The mean adsorption energy(E)values revealed that the adsorption mechanism of Cr and Pb(II)by CF-AC is physical in nature.The results of the study showed that adsorbent developed from CF-AC can be efficiently used as an environmentally friendly alternative adsorbent,for removal of Cr and Pb(II)ions in tannery wastewater.

Faujasite zeolite decorated with cobalt ferrite nanoparticles for improving removal and reuse in Pb^2+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 Pb^2+ions adsorption in an aqueous medium improving magnetic removal and reuse.As a result,a high surface area(434.4 m^2·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 Pb^2+ion adsorptive capacity(98.4%)in the first cycle.Around 98%of the Pb^2+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.

Synthesis of intracellular cobalt ferrite nanocrystals by extreme acidophilic archaea Ferroplasma thermophilum

Ferroplasma thermophilum,a sort of extreme acidophilic archaea,which can synthesize intracellular cobalt ferrite nanocrystals,is investigated in this study.The nanocrystals were analyzed with ultrathin sections and transmission electron microscope,with the size of 20−60 nm,the number of more than 30 in each cell at average,which indicated that F.thermophilum can synthesize intracellular nanocrystals and also belongs to high-yield nanocrystals-producing strain.Intriguingly,the nanocrystals contain ferrite and cobalt characterized by EDS X-ray analysis,suggesting that both cobalt and ferrite are potentially contributed to the formation of nanocrystals.Moreover,under the different energy source culture conditions of FeSO4 and CuFeS2,the size and the morphology of the nanocrystals are different.It was also found that the higher initial Fe availability leads to an induced synthesis of larger nanocrystals and the lower oxidation-reduction potential(ORP)leads to an induced effect on the synthesis of nanocrystals with abnormal unhomogeneous size,which suggested that the higher initial Fe availability and the lower oxidation-reduction potential lead to a higher uptake efficiency of iron ions of F.thermophilum by iron and ORP gradient culture.

Synthesis of carbon-coated cobalt ferrite core-shell structure composite:A method for enhancing electromagnetic wave absorption properties by adjusting impedance matching

Cobalt ferrite has problems such as poor impedance matching and high density,which results in unsatisfactory electromagnetic wave(EMW)absorption performance.In this study,the CoFe_(2)O_(4)@C core-shell structure composite was synthesized by a two-step hydrothermal method.X-ray diffraction,transmission electron microscopy,Fourier transform infrared spectroscopy,thermogravimetric analysis,and vector network analysis et al.were used to test the structure and EMW absorption properties of CoFe_(2)O_(4)@C composite.The results show that the reflection loss(RL)of the CoFe_(2)O_(4)@C composite reaches the maximum value of25.66 dB at 13.92 GHz,and the effective absorbing band(EAB)is 4.59 GHz(11.20-15.79 GHz)when the carbon mass content is 6.01%.The RL and EAB of CoFe_(2)O_(4)@C composite are increased by 219.55%and 4.59 GHz respectively,and the density is decreased by 20.78%compared with the cobalt ferrite.Such enhanced EMW absorption properties of CoFe_(2)O_(4)@C composite are attributed to the attenuation caused by the strong natural resonance of the cobalt ferrite,moreover,the carbon coating layer adjusts the impedance matching of the composite,and the introduced dipole polarization and interface polarization can cause multiple Debye relaxation processes.

Synthesis and characterization of carbon-coated cobalt ferrite nanoparticles

Cobalt ferrite nanoparticles（CFNPs） were prepared via a reverse micelle method. The CFNPs were subsequently coated with carbon shells by means of thermal chemical vapor deposition（TCVD）. In this process, acetylene gas（C2H2） was used as a carbon source and the coating was carried out for 1, 2, or 3 h at 750℃. The Ar/C2H2 ratio was 10：1. Heating during the TCVD process resulted in a NP core size that approached 30 nm; the thickness of the shell was less than 10 nm. The composition, structure, and morphology of the fabricated composites were characterized using X-ray diffraction, simultaneous thermal analysis, transmission electron microscopy, high-resolution transmission electron microscopy, and selected-area diffraction. A vibrating sample magnetometer was used to survey the samples＇ magnetic properties. The deposited carbon shell substantially affected the growth and magnetic properties of the CFNPs. Micro-Raman spectroscopy was used to study the carbon coating and revealed that the deposited carbon comprised graphite, multiwalled carbon nanotubes, and diamond-like carbon. With an increase in coating time, the intensity ratio between the amorphous and ordered peaks in the Raman spectra decreased, which indicated an increase in crystallite size.

Magnetic Nano Cobalt Ferrite Catalyzed Synthesis of 4H-Pyrano[3,2-h]quinoline Derivatives under Microwave Irradiation

A microwave irradiated magnetically separable nano cobalt ferrite catalyzed green method for the synthesis of 4-phenyl-4H-pyrano[3,2-h]quinolin-2-amine and 2-amino-4-phenyl-4H-pyrano[3,2-h] quinoline-3-carbonitrile derivatives through cyclization of aromatic aldehyde, acetonitrile/malononitrile and 8-hydoxyquinoline is developed and presented in this paper. The cubic magnetic cobalt ferrite nano particles were synthesized by sol-gel citrate precursor method and characterized by FT-IR, XRD, SEM and TEM techniques and the structures of the synthesized pyranoquinoline derivatives were assigned by IR, MASS and 1H NMR techniques. The reaction is carried out in a domestic microwave oven with a heat-resistant microwave safe glass container with a lid.

Templated synthesis of highly ordered mesoporous cobalt ferrite and its microwave absorption properties

Based on the nanocasting strategy, highly ordered mesoporous CoFe2O4 is synthesized via the ＇two-solvent＇ im- pregnation method using a mesoporous SBA-15 template. An ordered two-dimensional （P6mm） structure is preserved for the CoFe2O4/SBA-15 composite after the nanocasting. After the SBA-15 template is dissolved by NaOH solution, a mesoporous structure composed of aligned nanoparticles can be obtained, and the P6mm structure of the parent SBA-15 is preserved. With a high specific surface area （above 90 m2/g） and ferromagnetic behavior, the obtained material shows potential in light weight microwave absorption application. The minimum reflection loss （RL） can reach -18 dB at about 16 GHz with a thickness of 2 mm and the corresponding absorption bandwidth is 4.5 GHz.

Polypyrrole Chitosan Cobalt Ferrite Nanoparticles Composite Layer for Measuring the Low Concentration of Fluorene Using Surface Plasmon Resonance

Fluorene is a polycyclic aromatic hydrocarbon, which is a hazardous toxic chemical in the environment. The measurement of low concentrations of fluorene is a subject of intense interest in chemistry and in the environment. Polypyrrole chitosan cobalt ferrite nanoparticles are prepared using the electrochemical method. The prepared layers are characterized using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy. The layers are used to detect fluorene using the surface plasmon resonance technique at room temperature. The composite layer is evaluated after detection of fluorene using atomic force microscopy. The fluorene is bound on the layer, and the shift of the resonance angle is about 0.0052°, corresponding to the limitation of 0.01 ppm.

Structural and Electrical Properties of Cobalt Ferrite

Ferrites are a class of cohesive new materiafs required for many specialised applications. Cobalt ferrite (CoFe2O4) has been identified as a substitute for carbon and serves as a non consumable anode for an eco-friendly and energy efficient production of aluminium. Pellets of cobalt ferrite have been prepared by powder metallurgical process and their electrical properties have been investigated from ambient temperature to 1273 K. The structural and morphological features have been studied by X-ray diffraction and scanning electron microscopy The relationships between such properties, chemical composition and sintering temperatures are thoroughly discussed.

Dysprosium Modification of Cobalt Ferrite Ionic Magnetic Fluids

Dysprosium composite cobalt ferrite ionic magnetic fluids were prepared by precipitation in the presence of Tri-sodium citrate. Influence of dysprosium modification on magnetic property is studied. The result shows that magnetic response toward exterior magnetic field can be improved by adding Dy3+. Studies also show that the increase of reaction temperature may improve the modification effect of dysprosium. By adding dysprosium ions, the average diameter of the magnetic nanoparticles will be decreased evidently. It is clear that the particles appear as balls. Cobalt ferrite with sizes of 12-15 nm, rare earth composite cobalt ferrite with sizes of 6-8 nm.

Study of Structural, Electrical and Magnetic Properties of Manganese Doped Cobalt Ferrite Nanoparticles with Non-stoichiometric Composition

The nanoparticles of Co1＋xMnxFe2-xO4 （0≤x ≤ 0.5） ferrite system are synthesized by solid-state reaction route using planetary ball milling technique to investigate structural, electrical and magnetic properties. The X-ray diffraction patterns confirm the inverse spinel structure with residual oxide phases. Three distinct regions of frequency response on dielectric constant are observed Co1.2sMn0.5Fe1.75O4 as determined by the Wayne Kerr Impedance Analyzer. The first two regions of frequency response 1.13-4.5 MHz and 4.5-6.5 MHz exhibit the normal behavior but the last region 6.5-10.5 MHz indicates its anomalous behavior due to concurrent contribution of O^2-, Fe^3＋, Co^2＋ and Mn^3＋ ions in the relaxation process for sintering effects （sintered at 700℃）. This anomalous behavior is found to be pronounced and significant for the sample of composition Co1.25Mn0.25Fe1.75O4, which may be suitable to be used in the frequency band filter over wide range of frequencies. The single peak of imaginary part of dielectric constant （ε＂） indicates that the conduction process in this sample is due to the grain boundary resistance. The pronounced increase of capacitance （C） as observed from 100 ℃ to 125 ~C in temperature dependent measurement （30-125℃） is expected to eause from the change of polarization across the grain boundary due to redistribution of ions by the thermal agitation. The variation of resistance （R） with temperature （30-125 ℃） is found to exhibit semieonducting behavior that resulted from the p-type carriers （Co^2＋/Co^3＋）. A significant increase of Z from 105 ℃ with the increase of temperature indicates the signature of phase transition from ferrimagnetic-to-ferromagnetic, which may be ascribed to the increase of Co content. The appearance of the single semicircular arc in the Cole-Cole plot may be attributed to the contribution of grain boundary resistance and correspond to the parallel equivalent circuit of resistor-capacitor （R-C） combination with single relaxation time. Saturation magnetization of Co1.25Mn0.25Fe1.75O4 and Co1.375Mn0.375Fe1.625O4 is found to be greater than the literature value （61.5 emu/g） of un-doped cobalt ferrite in the measurement of their initial magnetization using Lakeshore vibrating sample magnetometer. The negative real part of AC permeability of Co1.5Mn0.5Fe1.5O4 signifies the diamagnetic behavior in the frequency range 0.13-25.2 MHz and expected to cause from the formation of magnetic dipoles opposite to the applied field due to Mn^2＋ in the B site. The samples are expected to be suitable for dielectric heating and high frequency applications.

Analysis of cerium substitution in Co-Sr based spinel ferrites for high frequency application

Spinel ferrites exhibit exceptional magnetic properties,making them a distinctive class of magnetic materials.The sol-gel technique was utilized for the synthesis of spinel ferrites with the chemical formula Co_(0.6)Sr_(0.4)Ce_(x)Fe_(2-x)O_(4). Following that,a comprehensive X-ray diffraction analysis unveiled the crystalline cubic structure of the synthesized materials.Through the utilization of the M-H loop approach,the ferromagnetic attributes of ferrites were assessed,and the assimilation of rare earth elements led to substantial enhancements in saturation magnetization,remanence,and coercivity.Spinel ferrites with a high concentration of rare earth elements have improved direct current resistivity and activation energy.The logarithm of a material's resistance increased from 5.29 to 8.12 Ω·cm as cerium is added.With a change in the amount of cerium,the activation energy goes up from 0.19 to 0.29.By changing the frequency from 5.5 to 9.5 GHz,the dielectric characteristics were determined.As the frequency goes up,the dielectric constant goes down.Spinel ferrites that have been made better in every way can be used in high-frequency applications.

CoFe_2O_4-Graphene Nanocomposites Synthesized through An Ultrasonic Method with Enhanced Performances as Anode Materials for Li-ion Batteries

Co Fe2O4-graphene nanosheets(Co Fe2O4-GNSs) were synthesized through an ultrasonic method, and their electrochemical performances as Li-ion battery electrode were improved by annealing processes. The nanocomposites obtained at 350 °C maintained a high specific capacity of 1,257 m Ah g-1even after 200 cycles at 0.1 A g-1. Furthermore,the obtained materials also have better rate capability, and it can be maintained to 696, 495, 308, and 254 m Ah g-1at 1, 2,5, and 10 A g-1, respectively. The enhancements realized in the reversible capacity and cyclic stability can be attributed to the good improvement in the electrical conductivity achieved by annealing at appropriate temperature, and the electrochemical nature of Co Fe2O4 and GNSs during discharge–charge processes.

Influence of particle size and temperature on the dielectric properties of CoFe_2O_4 nanoparticles

The objective of this study was to establish the dielectric properties of CoFe2O4 nanoparticles with particle sizes that varied from 28.6 to 5.8 nm. CoFe2O4 nanoparticles were synthesized using a chemical coprecipitation method. The particle sizes were calculated accord-ing to the Scherrer formula using X-ray diffraction （XRD） peaks, and the particle size distribution curves were constructed by using field-emission scanning electron microscopy （FESEM） images. The dielectric permittivity and loss tangents of the samples were determined in the frequency range of 1 kHz to 1 MHz and in the temperature range of 300 to 10 K. Both the dielectric permittivity and the loss tangent were found to decrease with increasing frequency and decreasing temperature. For the smallest CoFe2O4 nanoparticle size, the dielectric per-mittivity and loss tangent exhibited their highest and lowest values, respectively. This behavior is very useful for materials used in devices that operate in the microwave or radio frequency ranges.

Salt-assisted Low Temperature Solid State Synthesis of High Surface Area CoFe_2O_4 Nanoparticles

A novel salt-assisted low temperature solid state method using CoCl2.6H2O, FeCl3.6H2O and NaOH as precursor and using NaCI as a dispersant to synthesize high surface area CoFe2O4 nanoparticles, has been investigated. The effects of the molar ratio of added salt and calcination temperature on the characteristics of the products were investigated by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, vibrating sample magnetometer （VSM） and Brunauer, Emmett and Teller （BET） surface area analysis. Results showed that the introduction of leachable inert inorganic salt as a hard agglomeration inhibitor in the mixture precursor led to the formation of high dispersive CoFe2O4 nanoparticles; and the increase in specific surface area from 28.28 to 73.97 m^2/g, and the saturation magnetization is 84.6 emu/g.

CoFe_2O_4/carbon nanotube aerogels as high performance anodes for lithium ion batteries

High-performance lithium ion batteries(LIBs) require electrode material to have an ideal electrode construction which provides fast ion transport, short solid-state ion diffusion, large surface area, and high electric conductivity. Herein, highly porous three-dimensional(3D)aerogels composed of cobalt ferrite(CoFe_2O_4, CFO) nanoparticles(NPs) and carbon nanotubes(CNTs) are prepared using sustainable alginate as the precursor. The key feature of this work is that by using the characteristic egg-box structure of the alginate, metal cations such as Co^(2+)and Fe^(3+) can be easily chelated via an ion-exchange process, thus binary CFO are expected to be prepared. In the hybrid aerogels, CFO NPs interconnected by the CNTs are embedded in carbon aerogel matrix, forming the 3D network which can provide high surface area, buffer the volume expansion and offer efficient ion and electron transport pathways for achieving high performance LIBs. The as-prepared hybrid aerogels with the optimum CNT content(20 wt%) delivers excellent electrochemical properties, i.e., reversible capacity of 1033 mAh g^(-1) at 0.1 A g^(-1) and a high specific capacity of 874 mAh g^(-1) after 160 cycles at 1 A g^(-1). This work provides a facile and low cost route to fabricate high performance anodes for LIBs.

Synthesis and electromagnetic wave absorption properties of Gd-Co ferrite@carbon core-shell structure composites

Developing high-performance electromagnetic absorbing materials remains a challenge.In this work,Gd-Co ferrite@carbon core-shell structure composites were synthesized by a two-step hydrothermal method.The effects of rare earth Gd doping amount on the microstructure and electromagnetic wave absorption properties of cobalt ferrite@carbon composites were mainly studied.The results show that an appropriate amount of Gd doping can refine the crystal grain size of cobalt ferrite@carbon composites.However,when the doping amount of Gd exceeds the solid solubility threshold,the secondary phase GdFeO_(3)will be generated and the grain size will increase.When the doping amount of Gd is x=0.04,the reflection loss(RL) of the CoFe_(1.96)Gd_(0.04)O_(4)@C composites reaches the minimum value of -9.26 dB at the absorption layer thickness of 2.0 mm and a frequency of 13.67 GHz,and the effective absorption band(EAB) is 5.01 GHz(10.95-15.96 GHz).Compared with the CoFe_(2)O_(4)@C composites,the RL of the CoFe_(1.96)Gd_(0.04)O_(4)@C composites is increased by 79.35%,and the EAB is broadened by 3.51%.Gd ions enhance the dielectric loss through the grain size effect,and the increase of magnetocrystalline anisotropy enhances the magnetic loss.The CoFe_(1.96)Gd_(0.04)O_(4)@C composites have excellent impedance matching,which relies on the strong magnetic loss of ferrite,the interface polarization,and dipole polarization formed by the carbon shell to attenuate electromagnetic waves.

Effects of TbFeCo Underlayers on Magnetic Properties of CoFe_2O_4 Thin Films

Cobalt ferrite thin films were deposited on TbFeCo(10 nm)/Si(100) and Si(100) substrates at a substrate temperature of 350 ℃ by RF magnetron sputtering. The heat treated films were analyzed by Vibrating Sample Magnetometer (VSM) and X-Ray Photoelectron Spectroscopy (XPS). Results showed that all films had high coercivity and perpendicular anisotropy especially for the films deposited on TbFeCo underlayer. TbFeCo underlayers increase the coercivity, magnetization and remanence ratio of CoFe2O4 films, films on TbFeCo underlayer had coercivity and magnetization as high as 832×103 A·m-1 and 450×103 A·m-1, and its romance ratio reaches 0.9, which was related to the Tb3+ diffusion from the underlayer into the film.

Structural and magnetic properties of turmeric functionalized CoFe_2O_4 nanocomposite powder

The structural and magnetic properties of the synthesized pure and functionalized CoFe2O4magnetic nanoparticles(NPs) are studied by analyzing the results from the x-ray diffraction(XRD), transmission electron microscopy(TEM), FT–IR spectroscopy, thermogravimetry(TG), and vibrating sample magnetometer(VSM). To extract the structure and lattice parameters from the XRD analysis results, we first apply the pseudo-Voigt model function to the experimental data obtained from XRD analysis and then the Rietveld algorithm is used in order to optimize the model function to estimate the true intensity values. Our simulated intensities are in good agreement with the experimental peaks, therefore, all structural parameters such as crystallite size and lattice constant are achieved through this simulation. Magnetic analysis reveals that the synthesized functionalized NPs have a saturation magnetization almost equal to that of pure nanoparticles(PNPs). It is also found that the presence of the turmeric causes a small reduction in coercivity of the functionalized NPs in comparison with PNP. Our TGA and FTIR results show that the turmeric is bonded very well to the surface of the NPs. So it can be inferred that a nancomposite(NC) powder of turmeric and nanoparticles is produced. As an application, the anti-arsenic characteristic of turmeric makes the synthesized functionalized NPs or NC powder a good candidate for arsenic removal from polluted industrial waste water.

Efficient activation of sulfite for reductive-oxidative degradation of chloramphenicol by carbon-supported cobalt ferrite catalysts

Activation of(bi)sulfite(S(IV))by metal oxides is strongly limited by low electrons utilization.In this study,two carbon-supported cobalt ferrites spinels(CoFe^(2)O_(4) QDs-GO and CoFe^(2)O_(4) MOFs-CNTs)have been successfully synthesized by one-step solvothermal method.It was found that both catalysts could efficiently activate S(IV),with rapid reductive dechlorination and then oxidative degradation of a recalcitrant antibiotic chloramphenicol(CAP).Characterizations revealed that CoFe^(2)O_(4) spinels were tightly coated on the carbon bases(GO and CNTs),with effectiveness of the internal transfer of electrons.O_(2)˙−was identified for the reductive dechlorination of CAP,with simultaneously detection of both•OH and SO_(4)^(˙−)responsible for further oxidative degradation.The sulfur oxygen radical conversion reactions and molecular oxygen activation would occur together upon the carbon-based spinels.Spatial-separated interfacial reductive-oxidation of CAP would occur with dechlorination of CAP by O_(2)^(˙−)on the carbon bases,and oxidative degradation of intermediates by SO_(4)^(˙−/•)OH upon the CoFe^(2)O_(4) catalysts.