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Fossil fuel depletion and pollution are calling for alternative, renewable energies such as biofuels. Actual challenges include the design of efficient processes and catalysts to convert various feedstocks into biofuels. Here, we review nanoferrites heterogeneous catalysts to produce biodiesel from soybean and canola oil. For that, transesterification is the main synthesis route and offers simplicity, cost-effectiveness, better process control, and high conversion yield. Catalysis with nanoferrites and composites allow to obtain yields higher than 95% conversion with less than 5.0 wt.% of catalyst loading at 80 °C in 1–2 h. More than 90% conversion yields can be achieved with a moderate alcohol/oil molar ratio, i.e., between 12:1 to 16:1. Catalyst recovery is easy due to the magnetic properties of nanoferrite, which can be effectively reused up to 4 times with less than 10% loss of catalytic efficiency.

Samarium-doped cobalt ferrite nanoparticles CoSm x Fe 2- x O 4 (0 ≤  x  ≤ 0.1) were synthesized using citrate gel auto-combustion method, followed by annealing at 500 °C for 4 h in air. The physical properties of the samples were evaluated using x-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, Mössbauer, magnetic, and dielectric measurement techniques. Rietveld analysis of XRD data confirmed the formation of a single-phase cubic spinel structure for all compositions. Experimental results indicated that doping with samarium (Sm) strongly affected the magnetic properties of CoSm x Fe 2- x O 4 nanoparticles. The values of saturation magnetization ( M S ) were reduced from 62.99 ( x  = 0) to 41.17 ( x  = 0.1) emu/g. Room-temperature Mössbauer spectra show two sextets (tetrahedral and octahedral sites), and the values of the hyperfine magnetic field ( H hf ) of both sextets are found to decrease with Sm-doping. The values of the isomer shift show that all Fe-ions are found in the Fe 3+ state. The interstitial Sm ions positioned within CoFe 2 O 4 realized a dielectric constant dispersion that displayed a maximum at low frequency. With an increase in samarium ion concentration, the two dielectric relaxations reached a very wide range of frequencies. This can be attributed to the contribution of conduction in the grains and grain boundaries of ferrite. Samples with samarium contents of 0.01 and 0.03 showed high impedance stability at 50 and 150 °C, respectively, rendering them suitable for use as a high-frequency window below 1 kHz.

The synthesis of lanthanum (La) substituted Zn (Mn 0.6 Zn 0.2 La 0.2 Fe 2 O 4 ) and Fe (Mn 0.6 Zn 0.4 La 0.2 Fe 1.8 O 4 ) was performed using sol-gel auto-combustion techniques to investigate the effects of lanthanum doping on the structural and magnetic properties of Mn-Zn nanoferrites. X-ray diffraction and transmission electron microscopy confirmed the development of a single-phase spinel structure and a reduction in crystallite size (from 16 to 10.7 nm) with La substitution. Although saturation magnetization (M s ) decreased due to changes in cation distribution and magnetic interactions, La doping led to an increase in initial permeability. This enhancement was linked to changes in M s and the magneto-crystalline anisotropy constant (K 1 ). The permeability loss factor (tan δ µ ) remained low (around 10 − 2 ) for the La-doped ferrites, indicating minimal energy loss at room temperature. These results suggest promising potential for advanced biomedical applications, in line with Sustainable Development Goals (SDGs). The sol-gel auto-combustion technique provides a scalable and environmentally friendly method for synthesizing these materials, supporting SDG targets related to responsible consumption and production (SDG 12).

Using the sol-gel auto combustion approach, nanoferrites of the CoCr x Fe 2−x O 4 series (x = 0.00, 0.05, 0.10, 0.15, 0.20) are fabricated. Lattice constants are computed within the range of 8.312–8.375 Å, while crystallite size, estimated using Scherrer method yields ranges from 55.20 to 34.79 nm. Using Fourier transform infrared (FTIR) spectroscopy, different functional groups are found to correlate to different absorption bands. Five active modes are identified by Raman spectroscopy, revealing O 2− ion vibrations at both tetrahedral and octahedral locations. Throughout the series, ferromagnetic hysteresis loop is observed which is explained by Neel’s model. When the doping concentration increases in the Fe 2+ site the ac conductivity are found to decrease with increase in Cr 3+ doping content. With increasing frequency, both the dielectric constant and dielectric loss increase. In addition, with an increase in Cr 3+ doping, saturation magnetization ( M s ), remnant magnetization ( M r ), and coercivity ( H c ) show declining trends. For applications involving microwave devices, the sample CoCr 0.2 Fe 1.8 O 4 shows the most promising magnetic behavior, with M s ranging from 73.12 to 39.71 emu/g, M r from 37.77 to 20.64 emu/g, and H c from 1939 Oe to 1200Oe throughout the series.

The sol-gel auto-combustion method was used to synthesize copper nanoferrite and activated carbon-copper nanoferrite composite. The stoichiometric chemical proportions of Cu, Fe, and O were confirmed by EDX, and the porosity was checked by SEM of synthesized specimens. The spinel phase copper nanoferrite was confirmed by XRD. The octahedral and tetrahedral force constants were calculated using FTIR spectra of pristine and activated carbon–copper nanoferrite composite. The experiments of Methylene blue’s degradation in sunlight with H 2 O 2 and loading of synthesized specimens were carried out. The absorbance was checked for the degradation of MB using a UV-Visible spectrophotometer. It has been concluded that activated carbon-copper nanoferrite composite was more effective than spinel ferrites in degrading MB.

The sol-gel auto-combustion method synthesised Co 0.7 Cu 0.2 Zn 0.1 Fe 2−𝑥 Cr 𝑥 O 4 (x = 0.0, 0.05, 0.1, 0.15, 0.2, and 0.25) nano ferrite materials. Analytical techniques were employed to study their structural, electrical, and magnetic properties. Powder X-ray diffraction techniques were used to investigate the structural properties and confirm the single-phase formation. The lattice constants, ranging from 8.451 to 8.336 Å, were consistent with reported values. The average crystallite sizes of the products, estimated using the Scherrer equation, fell between 42.25 and 31.25 nm. Microstructural analysis revealed the formation of nano-sized particles. The synthesized samples exhibited increased crystallite grains, with an average size ranging from 38.7 nm to 52.6 nm, and particles in the form of accumulating spheres were observed in FESEM investigations. FTIR spectra confirmed the formation of the spinel structure. The semiconducting nature of the ferrites was inferred from their electrical characteristics, such as their electrical resistance to direct current (DC). Room temperature magnetic properties, measured using a vibrating sample magnetometer, showed that saturation magnetization increased with the highest dopant concentration. Conversely, the coercive field values fluctuated as a function of Cr 3+ doping. The size of crystallites, changes in the anisotropy constant, and cation distribution all impacted the coercivity behavior.

Water, being an essential element for the survival of living organisms, requires to be free from contaminants and pollutants. These contaminants are generally of organic, biological, microbial or inorganic nature, and all these contaminants pose severe hazards to human health upon consumption through the water. The high concentration of heavy metal ions is being found in water resources owing to the ever-increasing anthropogenic as well as industrial activities. Some of the heavy metals are crucial for the development and functioning of the human body, whereas some are toxic. In any case, consumption of any heavy metal beyond the accepted guideline values can lead to the rise of health complications. Researchers are effectively using magnetic nanoferrites as nanoadsorbents for water treatment. Specially designed magnetic nanoferrites have been found to provide as high as 99% elimination of selective heavy metal ions from the contaminated water. The present study reviews the recent researches conducted in the last two decades in the area of health hazards posed by prolonged consumption of heavy metal ions through consumable water and about using magnetic nanoferrites, their composites and derivatives for efficient removal of different kinds of heavy metal ions.

Magnesium nanoferrites are gaining a lot of scientific attention because of its magnificent dielectric characteristics such as large dielectric constant with minute dielectric losses, which make it suitable for potential applications such as high frequency, microwave devices, switching devices, power, magnetic storage devices, and many more. A series of manganese- and silver-substituted magnesium nanoferrites with the chemical composition Mg 1− y Mn y Ag x Fe 2− x O 4 (0.1 ≤  y  ≤ 0.4, 0.0 ≤  x  ≤ 0.3) were synthesized via sol–gel auto-combustion technique for reporting the electrical and dielectric study of synthesized specimens. In the present investigation, the dc resistivity ( ρ ) of prepared nanoferrites goes on decreasing as a function of Ag + and Mn 2+ concentrations extensively indicate its semi-conductor behavior. From the dielectric measurements, dielectric constant (∈′) increases with the increase in frequency, whereas the dielectric loss tangent (tan δ ) shows an inverse behavior with the increasing frequency, respectively. In relation with the dielectric investigations, AC conductivity ( σ ac ) shows similar behavior to that of dielectric constant. Therefore, such materials of high dielectric constant with minute dielectric losses make it suitable for the power application. Highlights Silver and manganese-doped magnesium nanoferrites were synthesized via sol–gel auto-combustion technique. Indicating semi-conductor behavior of synthesized samples. Dielectric constant (∈′) increases with very low dielectric losses (tan δ) which make it suitable for the power application.

In this work, the effects of Co x Zn 1- x Fe 2 O 4 ( x = 0, 0.5, 1) nanofillers on the PVDF polymer were scientifically studied. The structure and magnetic and optical properties were studied. XRD confirms the synthesis of nanofiller in a single phase. FTIR confirms the formation of nanoferrites. HRTEM shows that the prepared nanoferrites have a cubic-like shape. Also, the size and agglomeration increase with Co-Zn Fe 2 O 4 nanoferrites compared to the other singles one. The effect of adding nanoferrites into PVDF matrix was studied using XRD, FTIR, FESEM, VSM, and UV-Vis. XRD and FTIR approved the complexation between PVDF polymer and nanoferrites. Also, addition of nanoferrites into PVDF leads to decrease the semi-crystalline nature of PVDF. FESEM showed that embedding nanoferrites into PVDF polymers creates pores and PVDF/Co-Zn Fe 2 O 4 increases the pore size on the PVDF surface. The magnetic properties of PVDF were enhanced by adding the nanofiller. For example, saturation magnetization was increased from 269.31E −6 to 62.052E −3 by adding CoFe 2 O 4 to PVDF polymer. Band gap calculation showed that PVDF/Co-Zn Fe 2 O 4 has the lowest band gap energy which makes it useful in photochemical and electronic applications.

This study investigates the structural and magnetic properties of Gd-doped LaFeO₃ nanoferrites synthesized using the solution combustion method. X-ray diffraction analysis confirms the formation of orthorhombic perovskite structure, with lattice parameters decreases as Gd concentration increases up to 10%, indicating successful Gd substitution. The determined crystallite size reduces from 55 to 32 nm, and FESEM images reveal a more porous and finer-grained surface with increasing the Gd doping level. Magnetic measurements indicate that undoped LaFeO 3 exhibits weak antiferromagnetic behavior with negligible magnetization and no hysteresis. However, Gd doping significantly enhances magnetic performance. At 5 K, the saturation magnetization increases from 0 to 70 emu/g and coercivity from 0 to 18 Oe as Gd content reaches 10%. Notably, doped samples also maintain measurable magnetization and coercivity at 300 K, confirming improved room-temperature magnetic ordering. These enhancements are attributed to Gd-induced lattice distortions and the magnetic contribution of Gd 3+ ions, shifting the system toward weak ferromagnetism. The results demonstrate that Gd-doped LaFeO₃ is a promising material for spintronics and magnetic data storage applications.