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In this investigation, bentonite clay (BC) and bentonite clay@MnFe2O4 composite (BCMFC) were applied as efficient adsorbents for adsorbing Cr(III) and Cr(VI) ions from aqueous media. Different analyses such as FTIR, SEM, EDX, Map, BET, and XRD were used to characterize the adsorbents. The results showed that the removal efficiency of Cr(III) and Cr(VI) using BC were found to be 95.21 and 95.74%, while the corresponding values to the BCMFC were 97.37 and 98.65%, respectively. Also, the equilibrium and kinetic studies showed that the Freundlich isotherm model and the quasi-second-order kinetic model could better describe the equilibrium and kinetic behaviors of the adsorption process. The maximum adsorption capacity of the BC for the adsorption of Cr(III) and Cr(VI) ions were evaluated as 151.5 mg/g (25oC, pH 6, 90 min, and 1 g/L) and 161.3 mg/g (25oC, pH 3, 90 min, and 1 g/L), respectively, while the BCMFC showed the maximum capacities of 175.4 mg/g (25oC, pH 6, 60 min, and 1.5 g/L) and 178.6 mg/g (25oC, pH 3, 60 min, and 1.5 g/L) for Cr(III) and Cr(VI) ions, respectively, which were remarkable amounts. In addition, the thermodynamic study indicated that the adsorption process was physical, spontaneous, and exothermic. High removal efficiency, high chromium adsorption capacity, and low-cost magnetic adsorbent were significant features of the BCMFC for removal of Cr (III) and Cr (VI).

Dye in industrial wastewater is one of the most serious environmental concerns due to its potentially harmful effects on human health. Many industrial dyes are carcinogenic, toxic and teratogenic. Removal and recovery of hazardous dyes from the effluents requires efficient adsorbents. In this study, magnetic adsorbent MnFe 2 O 4 -NH 2 -HKUST-1 was synthesized to remove methylene blue and crystal violet dyes from aqueous solutions. The synthesized adsorbent was characterized using FTIR, XRD, BET, VSM, SEM, TGA and Zeta potential techniques. The effect of different parameters such as pH, contact time, and adsorbent dosage on the removal of dyes was investigated. The dye adsorption process was investigated by UV–Vis spectrophotometry. The maximum adsorbent capacity was obtained as 149.25 mg/g for methylene blue and 135.13 mg/g for crystal violet. The adsorption equilibrium isotherm and kinetic models were plotted and results showed that the adsorption process for both dyes is a collection of physical and chemical adsorption based on langmuir and freundlich isotherm models, and follows the pseudo-second-order adsorption kinetics. This study shows that magnetic adsorbent MnFe 2 O 4 -NH 2 -HKUST-1 has a good potential for removal of methylene blue and crystal violet dyes from water in a short time (5 min) and it is easily separated from the solution by a magnetic field due to its magnetic property.

The development of nanomaterials incorporating organic components holds significant importance in addressing the efficient removal of metal ions through adsorption. Hence, in this study, a novel MnFe 2 O 4 /chitosan/Schiff base nanocomposite was successfully synthesized by crosslinking MnFe 2 O 4 nanoparticles with functionalized chitosan using a novel Schiff base. The Schiff base was created through the condensation reaction between 2-aminophenol and terephthalaldehyde. Comprehensive characterization of the synthesized nanocomposite was performed through FT-IR, XRD, SEM, and VSM analyses, revealing a less crystalline arrangement compared to pure chitosan, a rough and non-uniform surface morphology, and a reduced magnetization value of 30 emu/g. Furthermore, the synthesized MnFe 2 O 4 /chitosan/Schiff base nanocomposite was working as an adsorbent for the effective disposal of Zn(II) ions from aqueous solutions. The synthesized nanocomposite exhibited a maximum sorption capacity of 289.86 mg/g for Zn(II) ions. Additionally, the results indicated that the removal of Zn(II) ions by the synthesized nanocomposite was a spontaneous, chemical, and endothermic process, aligning well with the Langmuir isotherm as well as the pseudo-second-order model. Furthermore, at pH 7.5, with a contact duration of 100 min and a temperature of 328 K, the fabricated nanocomposite reached its maximum sorption capacity for Zn(II) ions. The results of this study demonstrate the effectiveness of the newly synthesized MnFe 2 O 4 /chitosan/Schiff base nanocomposite in removing Zn(II) ions from aqueous media. The novel synthesis approach and the high adsorption capacity of 289.86 mg/g underscore the potential of this composite for practical applications in industrial wastewater treatment. The dual removal mechanism involving electrostatic attraction and complexation processes further enhances its utility, making it a valuable contribution to the field of environmental remediation.

MnFe2O4@TpPa-1 adsorbent was developed by co-precipitation and solvothermal method, using ?-ketoenamine linked covalent organic frameworks (COFs, TpPa-1) as supporting material to alleviate the aggregation of MnFe2O4. The properties were characterized by XRD, FT-IR, SEM, TEM, VSM, pHpzc, and N2 adsorption-desorption. The experimental results showed that the pseudo-second-order and Langmuir model best described the adsorption process, suggesting that the adsorption process was chemisorption and spontaneous endothermic reaction, and the maximum adsorption capacity of Bisphenol A (BPA) was 926.65 mg.g-1. The main adsorption mechanism of BPA was hydrogen bonding and ?-? conjugation between active functional groups in the TpPa-1 skeleton and BPA. Furthermore, the magnetic MnFe2O4@TpPa-1 showed good regeneration ability, indicating that MnFe2O4@TpPa-1 could be used in water treatment.

Au nanoparticles decorated mesoporous MnFe2O4 nanocrystal clusters (MnFe2O4/Au hybrid nanospheres) were used for the electrochemical sensing of As(III) by square wave anodic stripping voltammetry (SWASV). Modified on a cheap glass carbon electrode, these MnFe2O4/Au hybrid nanospheres show favorable sensitivity (0.315 μA/ppb) and limit of detection (LOD) (3.37 ppb) toward As(III) under the optimized conditions in 0.1 M NaAc-HAc (pH 5.0) by depositing for 150 s at the deposition potential of −0.9 V. No obvious interference from Cd(II) and Hg(II) was recognized during the detection of As(III). Additionally, the developed electrode displayed good reproducibility, stability, and repeatability, and offered potential practical applicability for electrochemical detection of As(III) in real water samples. The present work provides a potential method for the design of new and cheap sensors in the application of electrochemical determination toward trace As(III) and other toxic metal ions.

Thorough research on materials with negative permittivity is essential to address various application scenarios and their electromagnetic interference shielding capabilities must be carefully examined. This study focuses on the development of Bambuseae/MWCNT/MnFe 2 O 4 /PVA metacomposites through a simple sol–gel method. By adjusting the multi-walled carbon nanotubes (MWCNTs) content, the permittivity of the metacomposites was altered. When the MWCNT content was at 0.064 and 0.256 g, there was a noticeable observation of negative permittivity, mainly attributed to Lorentz model. The Bambuseae/MWCNT/MnFe 2 O 4 /PVA metacomposites showcased an exceptional shielding effectiveness of − 43.2827 dB for a thickness of 1 mm. The negative permittivity led to a significant impedance mismatch, causing the metacomposite surface to reflect the majority of electromagnetic waves. Moreover, the presence of plasma oscillations and the formation of conductive networks by MWCNTs enhanced the metacomposites’ ability to absorb electromagnetic waves within the material due to their high conductivity and polarization loss. Additionally, the Bambuseae/MWCNT/MnFe 2 O 4 /PVA metacomposites displayed remarkable optical-electrical conversion and remarkable durability in the production of flexible electronic devices like light-dependent resistors, indicating their potential use in harsh working conditions.

The widespread presence and use of Bisphenol A (BPA) in aquatic environments has caused significant ecological damage. Coal gangue (CG), a byproduct of coal mining, poses a major environmental concern due to its vast land occupation and potential for pollution. A magnetic recyclable geopolymer (MnFe2O4-CGP) using coal gangue geopolymer (CGP) as the carrier was successfully synthesized and was evaluated for its ability to Fenton-like degrade BPA. The characterization techniques revealed the successful incorporation of spherical MnFe2O4 onto the CGP surface and that CGP serves as an excellent platform for the immobilization and dispersion of MnFe2O4. The degradation rate reached 100% within 60 min at pH = 5, 15 mmol/L H2O2, 0.6 g/L catalyst, and 50 mg/L BPA, significantly higher than MnFe2O4 and CGP alone. It was indicated that the degradation rate of BPA in MnFe2O4-CGP composites was 0.1121 min−1, which was consistent with the first-order kinetic model. The saturation magnetization of MnFe2O4-CGP was measured to be 10.96 emu/g, enabling convenient recovery. MnFe2O4-CGP exhibited excellent stability, as the degradation rate of BPA remained above 95% even after five reaction cycles. This efficiency may be due to the MnFe2O4-CGP induced generation of reactive radicals. Quenching and EPR radical trapping experiments unequivocally confirmed that the reactive radical was hydroxyl radical (•OH). These results indicate that MnFe2O4-CGP has potential application prospects as a magnetic recyclable geopolymer composite in Fenton-like catalysis.

The extensive release of water contaminated with lead (Pb(II)) and antimony (Sb(V)) constitutes a serious threat to the human living environment and public health, necessitating immediate attention. In this study, a novel MnFe@SBA composite was synthesized using the hydrothermal method through the in situ growth of MnFe2O4 on SBA-15. The MnFe@SBA exhibits an amorphous structure with a high specific surface area of 405.9 m2/g and pore sizes ranging from 2 to 10 nm. Adsorption experiments demonstrated that MnFe@SBA removed over 99% of Pb(II) and 80% of Sb(V) within 120 min at initial concentrations of 10 mg/L, whereas both MnFe2O4 and SBA-15 exhibited poor adsorption capacities. Additionally, the MnFe@SBA displayed excellent tolerance towards coexisting cations, including Na+, K+, Mg2+, Ca2+, Zn2+, Ni2+, and Cd2+, as well as anions such as Cl−, NO3−, CO32−, and PO43−. The adsorption behavior of Pb(II) onto MnFe@SBA was satisfactorily described by the pseudo-second-order kinetic model and the Freundlich isotherm, while the adsorption of Sb(V) was well-fitted by the pseudo-second-order kinetic model and the Langmuir isotherm. At 318 K, the maximum adsorption capacities of MnFe@SBA for Pb(II) and Sb(V) were determined to be 329.86 mg/g and 260.40 mg/g, respectively. Mechanistic studies indicated that the adsorption of Pb(II) and Sb(V) onto MnFe@SBA involved two primary steps: electrostatic attraction and complexation. In conclusion, the MnFe@SBA is anticipated to serve as an ideal candidate for efficient removal of Pb(II) and Sb(V) from contaminated water.

Nanomaterials were widely used as efficient adsorbents for environmental remediation of tetracycline pollution. However, the separation of the adsorbents posed the challenge to their practical applications. In this study, we grew magnetic MnFe 2 O 4 nanoparticles on the reduced graphene oxide (rGO) to form MnFe 2 O 4 /rGO nanocomposite with a one-step method. When used as the absorbent of Tetracycline, it exhibited an adsorption capacity of 41 mg/g. The adsorption kinetics and isotherm were fitted well with the pseudo-second order model and Freundlich model, respectively. The MnFe 2 O 4 /rGO nanocomposite could be easily extracted from the solution with the external magnetic field and regenerated with acid washing.

Transition metal oxides (TMOs) are important anode materials in sodium-ion batteries (SIBs) due to their high theoretical capacities, abundant resources, and cost-effectiveness. However, issues such as the low conductivity and large volume variation of TMO bulk materials during the cycling process result in poor electrochemical performance. Nanosizing and compositing with carbon materials are two effective strategies to overcome these issues. In this study, spherical MnFe2O4@xC nanocomposites composed of MnFe2O4 inner cores and tunable carbon shell thicknesses were successfully prepared and utilized as anode materials for SIBs. It was found that the property of the carbon shell plays a crucial role in tuning the electrochemical performance of MnFe2O4@xC nanocomposites and an appropriate carbon shell thickness (content) leads to the optimal battery performance. Thus, compared to MnFe2O4@1C and MnFe2O4@8C, MnFe2O4@4C nanocomposite exhibits optimal electrochemical performance by releasing a reversible specific capacity of around 308 mAh·g−1 at 0.1 A·g−1 with 93% capacity retention after 100 cycles, 250 mAh·g−1 at 1.0 A g−1 with 73% capacity retention after 300 cycles in a half cell, and around 111 mAh·g−1 at 1.0 C when coupled with a Na3V2(PO4)3 (NVP) cathode in a full SIB cell.