Heat Treatment Effects on Structural-Magnetic Properties and Congo Red Adsorption Performance of Sn0.5Ni0.3Mn0.2Fe2O4 Nanoferrites
摘要
Mixed tri-metal spinel ferrites show improved optical, structural, catalytic, dielectric, and magnetic properties compared to mono- and di-spinel ferrites. Optimizing heat treatment parameters for mixed metal ferrite nanoparticles is crucial for enhancing their performance in environmental applications such as dye removal. This study demonstrates that optimizing heat treatment conditions provides a facile approach to tune the structural-magnetic properties of mixed metal ferrites for enhanced environmental remediation applications. This work studied mixed metal magnetic spinel ferrite Sn0.5Ni0.3Mn0.2Fe2O4 samples, which were synthesized via co-precipitation at different heat treatment conditions, namely 600–750°C for 2–6 h. The X-ray diffraction (XRD) indicates that increasing the heating time led to the contraction of the spinel ferrite lattice parameter aF. However, increasing the temperature led to the expansion of aF, with the formation of α-Fe2O3 and SnO2. Transmission electron microscope (TEM) images reveal an increase in the grain size with increased heat treatment times and temperatures, while selected area electron diffraction (SAED) supported the XRD results. Scanning electron microscope (SEM) showed significant effects of heat treatment conditions on the samples, while the energy dispersive X-ray (EDX) technique proved that the real composition of synthesized samples was a closer theoretical one. Fourier transform infrared (FTIR) spectroscopy verified the presence of characteristic M–O bonds of spinel ferrite in the prepared samples. Notably, the Debye temperature, an indicator of lattice vibration and thermal stability, increased from 733.83 K to 747.01 K with rising heat treatment temperature, and from 724.82 K to 730.71 K with longer heating time, indicating enhanced bond strength and lattice rigidity. UV-visible spectra analysis revealed that the optical band gap energy follows a typical quantum confinement effect trend, decreasing from 3.228 to 2.885 eV as the particle size grew from 10.89 to 19.88 nm. Raman spectra confirmed the formation of the ferrite structure and found that increasing either the heating time or temperature favored the migration of Fe cations from tetrahedral into the octahedral sites. X-ray photoemission spectroscopy (XPS) confirmed the elemental distribution of Sn, Mn, Ni, and Fe, supporting the formation of a mixed spinel ferrite structure in the prepared samples. Increasing the heating time improves magnetic properties such as remnant magnetization (Mr) and coercivity field (Hc). Meanwhile, increasing the heating temperature massively raises all magnetization parameters. Dye adsorption studies revealed that ferrite heat treated at 600 °C for 6 h exhibited the highest Congo Red removal efficiency (60.63%), correlating with its enhanced magnetic properties Mr: 2.03 emu/g and Hc: 107.17 Oe.