Novel magnetically recoverable MnFe2O4/TiO2 nanocomposites synthesized using green route for photocatalytic degradation of methylene blue

Abstract

The photocatalytic degradation of hazardous organic dyes was investigated using green-produced MnFe₂O₄/TiO₂ nanocomposites, which demonstrated magnetic reusability and separability, making them efficient photocatalysts for rapid UV degradation. The MnFe₂O₄/TiO₂ diffraction peaks indicated a single-phase cubic spinel structure, with crystallite sizes spanning from 5.3 to 7.1 nm. The TiO₂ anatase phase showed typical peaks at 25.8° and 48.2°, corresponding to the (110) and (200) diffraction planes, respectively. The transmission electron microscopy image of MnFe₂O₄/TiO₂ revealed inter-grain aggregation between the particles. The particle size of MnFe₂O₄/TiO₂ exhibited a slight increase from 30 to 40 nm. MnFe₂O₄ appeared as black spheres, whereas TiO₂ appeared as grey circles. X-ray spectroscopy confirmed the matching of chemical elements. The bandgap of the nanocomposites decreased from 2.9 to 3.2 eV after the surface treatment with TiO₂, indicating an electronic transition between the two components. Furthermore, the addition of TiO₂ affected the saturation magnetization, which ranged from 7.6 to 11.2 emu/g. The nanocomposites clearly displayed superparamagnetic-like behavior. A photocatalytic investigation showed that MnFe₂O₄/TiO₂ nanoparticles exhibited higher photocatalytic activity than MnFe₂O₄ nanoparticles. Methylene blue dye was degraded by 98 % using the MnFe₂O₄/TiO₂ nanocomposites after 2 h of UV exposure. This photodegradation was further investigated using a Langmuir–Hinshelwood kinetic model, and it was discovered that the rate constant (K_app) increased with the TiO₂ concentration. The nanocomposites maintained over 90 % photocatalytic efficiency without any significant degradation after three reuse cycles. Therefore, green-synthesized MnFe₂O₄/TiO₂ nanocomposite photocatalysts for dye degradation are highly promising for the removal of harmful organic dyes from the environment.