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ZnFe 2 O 4 is a significant byproduct of the zinc metallurgical process. Research on its recovery and utilisation has been shown to reduce resource waste and play a positive role in achieving comprehensive resource utilisation in the zinc metallurgical process. This study utilised a piecewise interpolation method to calculate the zinc leaching rate of pure zinc ferrite under specific experimental conditions. This approach was informed by previous acid leaching data for pure zinc ferrite and zinc calcine. A comparative analysis was conducted on the Zn and Fe leaching rates from zinc ferrite within zinc calcine under identical experimental conditions. The objective of this analysis was to identify suitable conditions for preparing and purifying zinc ferrite. The findings suggest that zinc ferrite products can be effectively separated and purified under conditions of acid concentration levels greater than 120 g/L, leaching temperature of 75 °C, and leaching time from 150 minutes to 180 minutes; or an H 2 SO 4 concentration greater than 200 g/L, an ambient leaching temperature at 75 °C, and a leaching time from 60 minutes to 90 minutes.

Ferrites; MFe 2 O 4 ( M  = Co, Ni, Cu, Mg ,and Zn) nanocrystals were prepared using sucrose auto-combustion. X-ray diffraction showed complete formation of ferrites with tetragonal structure for CuFe 2 O 4 and cubic for all others. Fourier transform-infrared confirmed ferrites' formation, and the obtained data were used to estimate the different elastic properties. Transmission electron microscopy exhibited agglomerated spherically shaped clusters for CoFe 2 O 4 , MgFe 2 O 4 , and ZnFe 2 O 4 while NiFe 2 O 4 and CuFe 2 O 4 showed cubic morphology. Magnetic measurements via vibrating sample magnetometer revealed ferromagnetic properties of all ferrites except for ZnFe 2 O 4 indicating paramagnetic one. The coercivity measurements indicated magnetically hard ferrites for CoFe 2 O 4 and CuFe 2 O 4 , while others showed soft magnetic. ac-conductivity indicated semiconducting properties with a magnetic phase transition from ferro- to paramagnetic for all ferrites except for CoFe 2 O 4 . The deviation from Arrhenius plots at > 500 K revealed the conduction mechanism change from electron hopping to polaron conduction. This change was also proved via conductivity vs. frequency and through dielectric relaxation. Graphical abstract XRD indicated cubic structure for all the studied ferrites except for CuFe 2 O 4 which showed tetragonal structure.

One major cause of to environmental pollution is industrial dye wastewater. The main purpose of current work was synthesis and investigation of effectiveness of LDH–Ferrite–Biochar–Polymeric composites for removal of anionic dye (Acid blue 41) from wastewater. The co-precipitation technique is used to synthesize Zn–Al Layered double hydroxide-Manganese ferrite–Egg Shell biochar–Starch (Zn–Al–MnFe 2 O 4 –ESB–Sta), Cu–Al Layered double hydroxide–Cadmium ferrite–Eucalyptus bark biochar–Chitosan (Cu–Al–CdFe 2 O 4 –EBB–Cs), Cd–Al Layered double hydroxide–Cobalt ferrite–Jujube wood biochar–Sodium alginate (Cd–Al–CoFe 2 O 4 –JWB–Na–Alg), Mn–Al Layered double hydroxide–Copper ferrite–Mulberry Stem Biochar–Starch (Mn–Al–CuFe 2 O 4 –MSB–Sta) and Co–Al Layered double hydroxide–zinc ferrite-peanut shell biochar–carboxymethyl cellulose (Co–Al–ZnFe 2 O 4 –PSB–CMC). According to findings of recent studies, Zn–Al–MnFe 2 O 4 –ESB-Sta (40.1 mg/g), Cu–Al–CdFe 2 O 4 –EBB–Cs (35.6 mg/g), Cd–Al–CoFe 2 O 4 –JWB–Na–Alg (28.1 mg/g), Mn–Al–CuFe 2 O 4 –MSB-Sta (37.3 mg/g) and Co–Al–ZnFe 2 O 4 –PSB–CMC (31.2 mg/g) has adsorption capacity for acid blue 41 dye. All composites achieved maximum adsorption effectiveness in acidic range (2–5), eliminating AB-41 dye in 45 min at optimal dose 0.05 g and 150 mg/l initial dye concentration was optimum. After 30 °C, adsorption potential decreased, indicating exothermic mechanisms. The efficiency was still adequate after five cycles of regeneration. The Pseudo 2nd order Kinetics and Freundlich isotherm model were successfully implemented among the applied models. The aforementioned composites are deemed the most cost-effective, energy-efficient, ecologically friendly, and biologically renewable materials for treating wastewater containing AB-41 dye. The results indicate that Zn–Al–MnFe 2 O 4 –ESB–Sta is the most effective synthetic composite for water remediation among all others. Furthermore, it was discovered in a column study that the ideal bed height, flow rate, and inlet concentration of dye were 3 cm, 3.6 ml/min, and 50 mg/l, respectively, for achieving the highest adsorption of AB-41 dye. Graphical Abstract

This study is an attempt to compare the hyperthermia and antimicrobial activity of three members of the family of spinel ferrite magnetic nanoparticles (XFe 2 O 4 , where X = Mg, Cu, and CO) MNPs. Spinell ferrite of MgFe 2 O 4 , CuFe 2 O 4 , and CoFe 2 O 4 were prepared via sol–gel method. Structural and morphological shapes were investigated by different techniques X-ray diffraction X-ray powder diffractometer (XRD), Fourier transformed infrared spectroscopy (FTIR), and (Transmission electron microscope) TEM. Magnetic properties were examined by vibrating sample magnetometer (VSM). The in vitro test was conducted on cervical Hela cells using an MTT assay. Finally, the antimicrobial activity was tested on Staphylococcus aureus , Bacillus subtlus , and Escherichia coli using a clearing inhibition zone. XRD results confirmed the crystalline nature of MgFe 2 O 4 , CuFe 2 O 4 , and CoFe 2 O 4 . VSM results showed a high maximum saturation (Ms = 44.87 emu/g) of CuFe 2 O 4 which is greater than that of CoFe 2 O 4 and MgFe 2 O 4 (18.221 and 18.669) emu/g, respectively. MTT assay revealed that high cell death was detected on Hela cells of CuFe 2 O 4 compared to that of MgFe 2 O 4 and CoFe 2 O 4 . The anti-microbial study showed that the prepared spinel magnetic nanoparticles possessed antimicrobial activity due to the release of Mg, Cu, Co, and Fe ions. Results showed that the CuFe 2 O 4 could be a good spinel ferrite for medical application with antimicrobial activity and generate heat (hyperthermia, anti-cancer material).

In this study, novel nanocomposites of CoFe 2 O 4 , CoFe 2 O 4 /MWCNTs, Co 0.5 Zn 0.5 Fe 2 O 4 , and Co 0.5 Zn 0.5 Fe 2 O 4 /MWCNTs were synthesized using the sol–gel and one-pot wet-impregnation method and further applied in the form of electrode material for their supercapacitor applications. The structural and optical properties of the as-synthesized electrode materials were investigated via X-ray diffraction, Fourier transform infrared, and Diffuse reflectance spectroscopic techniques. These materials exhibited crystallinity evident from X-ray diffraction analysis. No additional peak was envisioned upon addition of Zn to the crystal structure of CoFe 2 O 4 , which confirmed doping of Zn into CoFe 2 O 4 . Morphological analysis inferred the incorporation of synthesized ferrites into MWCNTs. The scanning electron micrographs further demonstrated a highly porous framework that provided enhanced ion transportability as well as high surface area for substantial charge storage. The electrochemical performance was evaluated using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy for supercapacitors applications. All of these synthesized materials demonstrated good electrochemical potential, but MWCNTs-supported ferrite nanocomposites attained higher specific capacitance (CV; 175 F g −1 & 590 F g −1 , 418 F g −1 & 1123 F g −1 at 15 mV s −1 , GCD; 19 F g −1 & 217 F g −1 , 95 F g −1 & 832 F g −1 at current density of 0.1 A g −1 ) for CoFe 2 O 4 , CoFe 2 O 4 /MWCNTs, and Co 0.5 Zn 0.5 Fe 2 O 4 , Co 0.5 Zn 0.5 Fe 2 O 4 /MWCNTs with capacitance retention of 92% and 95% after 2000 stability cycles, respectively. This inferred that CoFe 2 O 4 /MWCNTs and Co 0.5 Zn 0.5 Fe 2 O 4 /MWCNTs have the potential to be used for capacitive storage as well as in optical electronics due to their structural and good electrochemical properties. Graphical Abstract

In this paper, the law of approach to saturation (LAS) was applied to a series of Mn–Zn ferrite nanoparticles with compositional formula Mn1−xZnxFe2O4 where x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5 to study the dependence of magnetization, M, on the applied magnetic field, H. Using the statistical parameters, the field range was chosen. The dependence of magnetization on the applied field was studied based upon the output of the statistical parameters for the curve fitted using different forms of LAS, namely, M=Ms1−aH−bH2+kH , M=Ms1−aH−bH2,M=Ms1−bH2 and M=Ms1−115HA2H12H32+HR32+kH . A critical examination on the output parameters resulted from fitting into different equations, indicates the dependency of magnetization on the applied field as a characteristic of the composition of Mn–Zn ferrites. The statistical parameters, along with physically meaningful fitted parameters, provide knowledge on dependency of magnetization of different compositions of Mn–Zn ferrites over different regions of applied field.

The present study aimed to understand the structural, magnetic, and electrical features of MFe 2 O 4 nanocrystals (M = Mg 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ) synthesized via simple co-precipitation route and doing a comparative study with materials prepared using other routes. XRD showed the single-phase cubic structure formation for the samples only after calcination at 700 o C. An exception was obtained with MgFe 2 O 4, which retains the Fe 2 O 3 secondary phase, and CuFe 2 O 4, which showed a structure transformation into a tetragonal phase. FT-IR spectroscopy indicated the pronouncing of the atomic weight effect on the ionic radii when discussing the present difference in the bands` positions. Agglomerated sphere-like cluster morphologies were detected through a TEM study. Magnetic studies showed ferromagnetic properties for CoFe 2 O 4 and CuFe 2 O 4 , as well as superparamagnetic properties for the other ferrites. Also, only CoFe 2 O 4 and CuFe 2 O 4 showed hard ferrite types, while others indicated soft ones. The electrical investigations exhibited semi-conducting properties for all the samples, accompanied by a transition in the conduction mechanism from hopping to polaron as the temperature rose. The obtained conductivities order is CuFe 2 O 4 > CoFe 2 O 4 > ZnFe 2 O 4 > NiFe 2 O 4 > MgFe 2 O 4 . The low dielectric values obtained suggest the use of entire ferrites in microwave applications.

We review the basic phenomenology of magnetic losses from DC to 1 GHz in commercial and laboratory-prepared soft ferrites considering recent concepts regarding their physical interpretation. This is based, on the one hand, on the identification of the contributions to the magnetization process provided by spin rotations and domain walls and, on the other hand, the concept of loss separation. It additionally contemplates a distinction between the involved microscopic dissipation mechanisms: spin damping and eddy currents. Selected experimental results on the broadband behavior of complex permeability and losses in Mn-Zn ferrites provide significant examples of their dependence on sintering methods, solute elements, and working temperature. We also highlight the peculiar frequency and temperature response of Ni-Zn ferrites, which can be heavily affected by magnetic aftereffects. The physical modeling of the losses brings to light the role of the magnetic anisotropy and the way its magnitude distribution, affected by the internal demagnetizing fields, acts upon the magnetization process and its dependence on temperature and frequency. It is shown that the effective anisotropy governs the interplay of domain wall and rotational processes and their distinctive dissipation mechanisms, whose contributions are recognized in terms of different loss components.

Cobalt ferrite, Copper ferrite and cobalt doped copper ferrite nanoparticles have been synthesized and characterized using different characterization methods (XRD, FTIR and FESEM). The prepared nanoparticles have been used as promising fillers of the polyvinylidene fluoride (PVDF) polymer. The PVDF/(Cu–CoFe 2 O 4 , CoFe 2 O 4 , and CuFe 2 O 4 ) nanocomposites films have been prepared via a simple solution casting technique. The optical properties and the piezoelectric response of the prepared nanocomposite films have been studied. This study showed that Cu–CoFe 2 O 4 and CoFe 2 O 4 , have enhanced the interfacial polarization density and dielectric constant. The prepared nanofillers reduced the PVDF band gap energy value. The optical conductivity value of PVDF/(Cu–CoFe 2 O 4 and CoFe 2 O 4 ) increased five times compared with the pure PVDF. Also, an increase in the piezoelectric response has been recorded by adding the nano-fillers to the pure PVDF.