Composite CoFe2O4 Research Articles

Construction of Magnetic S‐Doped CoWO4 Composite for Efficient and Selective Recovery of Gold from Wastewater via Adsorption–Reduction Pathway

The design and synthesis of efficient adsorbents for the recovery of precious metals from secondary resources are of great environmental and economic significance. Herein, a magnetic sulfur‐doped composite CoFe2O4@S–CoWO4 (CF@S–CoWO4) is developed through a hydrothermal synthesis method, which is used to selectively recover gold in aqueous media. Significantly, CF@S–CoWO4 exhibits the best overall performance with gold ions adsorption capacity (Qmax) and distribution coefficient (Kd) are 1049 mg g−1 and 4.4 × 106 mL g−1, respectively, which are much higher than those of other gold adsorption materials. The selectivity coefficients (K) toward other metal ions (Pd2+, Ca2+, Mg2+, Cd2+, Al3+, Li+, Ni+) are also higher, which suggests that CF@S–CoWO4 had a preferential selectivity for Au3+ in coexisting ion solutions. Moreover, the antianion interference of the composite follows the order: SO42− > PO43− > NO3− > CO32−, and it also shows very good reusability with adsorption efficiency at 81.78% after four repeated cycles. Based on characterizations and calculation, it is found that Au(III) mainly undergoes chelation and reduction reactions in the S sites in CF@S–CoWO4, which indicates the important role of S sites. Hence the CF@S–CoWO4 composite demonstrates a promising application for the recycling of gold ions from electronic wastewater.

Nitric acid assisted sol-gel synthesis of cobalt ferrite nano particles

Mono-phase cobalt ferrite nanoparticles possessing excellent magnetostrictive properties having the composition CoFe2O4 was synthesized employing sol gel technique with an acid catalyst. The acidic environment was facilitated using nitric acid. The dried gel was calcined at about 800 °C and the phase formation for the same was studied using X-ray diffraction (XRD). The calcined powder was further analyzed with Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Band gap for the ceramic sample was calculated using UV-visible spectroscopy.

Highly Efficient Adsorption of Heavy Metals onto Novel Magnetic Porous Composites Modified with Amino Groups

A novel porous magnetic composite CoFe2O4–SiO2 (CF–S) was prepared by a simple template method. After facile amino-functionalization, it exhibited bigger adsorption capacity and higher removal efficiency (>90%) for all the heavy metal ions (Cu(II), Mn(II), Cd(II), and Pb(II)) in single or mixed metal ions solution. The adsorption affinity for heavy metal ions was not much impacted by the presence of competitive ions. Moreover, effects of experimental parameters, including adsorbent dosage, solution pH, initial concentration, reaction temperature and time, were discussed. The isothermal adsorption results were well described by the Langmuir model, and the maximum adsorption capacities were 429.18 mg·g–1 (25 °C), 500.00 mg·g–1 (35 °C), 523.56 mg·g–1 (45 °C), and 555.51 mg·g–1 (55 °C) for Cu(II) ions. The adsorption kinetics fitted well with pseudo-second order kinetic model. Analysis of thermodynamic study for Cu(II) showed that the process of adsorption was spontaneous and endothermic in nature. The result...

Investigation of superparamagnetism in pure and chromium substituted cobalt nanoferrite

Nanostructured magnetic materials with the chemical composition CoFe2O4 and CoCr0.9Fe1.1O4 were synthesized through Citrate-gel chemical synthesis with a crystallite size of 6.5nm and 10.7nm respectively. Structural characterization of the samples was performed by X-ray diffraction analysis and magnetic properties were studied using Vibrating Sample Magnetometer (VSM). Magnetization measurements as a function of applied magnetic field ±10T at various temperatures 5K, 25K, 310K and 355K were carried out. Field cooled (FC) and Zero field cooled (ZFC) magnetization measurements under a magnetic field of 100Oe for temperature ranging from 5–400K were studied. The blocking temperature (Tb) for both the ferrites was observed to be around 355K. Below blocking temperature they showed ferromagnetic behavior and above which they are superparamagnetic in nature that favors their application in the biomedical field. The substitution of paramagnetic Cr3+ ions for magnetic Fe3+ ion in cobalt ferrite has resulted in a decrease in magnetization and the coercivity of the samples. CoCr0.9Fe1.1O4 nanoferrites with observed low coercivity of 338Oe make them desirable in high frequency transformers due to their very soft magnetic behavior.

CoFe/SBA-15 catalyst coupled with peroxymonosulfate for heterogeneous catalytic degradation of rhodamine B in water

CoFe/SBA-15 catalysts were prepared by simultaneous incipient wetness impregnation using Co(NO3)2·6H2O and Fe(NO3)3·9H2O as the precursors and SBA-15 as the support. The catalysts were used to activate generation of sulfate radicals from peroxymonosulfate (PMS) for rhodamine B (RhB) dye degradation in aqueous solutions. The catalyst was characterized using X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy and energy-dispersive X-ray spectroscopy, transmission electron microscopy, and vibrating sample magnetometry. The effects of the Co and Fe loadings and calcination temperature on the catalytic performance, catalyst reusability, and kinetics and mechanism of catalytic oxidative degradation of RhB in the presence of CoFe/SBA-15 and PMS were investigated. The results show that the predominant Co-Fe oxide loaded on the support was the composite CoFe2O4, which provided the active catalytic sites, and was present in the SBA-15 matrix. The surface area, pore volume, and mean pore diameter of 10Co9.5Fe/SBA-15-700 were 506.1 m2/g, 0.669 cm3/g, and 7.4 nm, respectively, lower than those of SBA-15. 10Co9.5Fe/SBA-15-700 consisted of rod-like aggregates with diameters greater than 0.25 μm. It had a magnetic intensity of 8.3 emu/g; therefore, magnetic separation was feasible. 10Co9.5Fe/SBA-15-700 showed good catalytic activity and stability, with a RhB degradation rate higher than 96% and Co leaching lower than 32.4 μg/L. The catalytic oxidative degradation of RhB in the presence of FeCo/SBA-15 and PMS obeyed first-order kinetics, and the degradation rate increased with increasing CoFe/SBA-15 and PMS dosages and with decreasing initial reactant concentrations. Quenching tests showed that sulfate radicals played a dominant role in RhB catalysis. CoFe/SBA-15 maintained high catalytic activity and good stability during 10 recycling runs, with a RhB degradation rate greater than 84%, Co and Fe leaching for each run lower than 72.1 and 35 μg/L, respectively. CoFe/SBA-15 is an efficient catalyst for PMS oxidation, and has potential applications in the removal of refractory organics such as RhB in water.

The structure and magnetic properties of cobalt ferrite nanoparticles synthesized in a system of direct micelles of amphiphiles by means of ion flotoextraction

A method for obtaining nanoparticles in a system of direct micelles of amphiphiles using ion flotoextraction for concentrating ions from diluted water solutions is developed. Nanoparticles of the composition CoFe2O4 with a structure close to spinel are obtained. It is established that the particles consist of two components: well-formed phases of cobalt ferrite CoFe2O4 and its amorphous analog. It is shown that the nanoparticles have a maximum size distribution ranging from 4 to 6 nm; on a carbon substrate, they self-organize into a periodic colloidal structure. It is concluded that nanosized CoFe2O4 powder has a blocking temperature of about 45 K, a magnetic moment of about 0.85–0.9μB at a temperature of 0 K, and the Neol temperature lies in the range of 110 to 250 K.

Temperature studies of Co-ferrite magnetostriction

The magnetostriction λ and the coercive force Hc are investigated here for a ferrite of the approximate composition CoFe2O4 (Co2O3, 40.92 wt.%; Fe2O3, 59.08 wt.%) from room temperature to the Curie temperature Θ. The resulting data is analyzed.