Magnetically separable and reusable Fe3O4/chitosan nanocomposites green synthesized utilizing Moringa oleifera extract for rapid photocatalytic degradation of methylene blue

Abstract

This study focused on the green synthesis of Fe3O4/Chitosan (Cs) nanocomposites using Moringa oleifera leaf extract, which showed good photocatalytic activity when exposed to ultraviolet (UV) irradiation. X-ray diffraction spectrum of Fe3O4/Cs informs the cubic inverse spinel and has crystallite size in the 10.1 – 11.7 nm range. The crystallite size also increased with the increase of Cs mass. The morphology of Fe3O4 and Fe3O4/Cs was nearly spherical. The transmission electron microscope showed the most uniform size of nanocomposites at around 17.1 nm. The Fourier transform infrared spectrophotometer result identified Fe-O in the 576–583 cm−1 range, indicating that Fe3O4 successfully bonded to Cs. Other functional groups, including O–H, C–H, C–O, C–O–C, and NH2, were also found, indicating that the formation of Cs was effective. The element composition of Fe3O4 is Fe (70.9 %) and O (29.1 %). Meanwhile, Fe3O4/Cs (4:4) is 47.9 %, 36.4 %, 11.3 %, and 4.4 % for Fe, O, C and N, respectively. The hysteresis curve indicated that Fe3O4 and Fe3O4/Cs nanocomposites have soft ferromagnetic properties. Meanwhile, the saturation magnetization of Fe3O4 and Fe3O4/Cs (4:2) nanocomposites are 54.0 and 42.3 emu/g, respectively. Peaks are seen in the UV–visible absorption spectrum of Fe3O4 and Fe3O4/Cs nanocomposites between wavelengths 365–377 nm. The optical band gap energy (Eg) of Fe3O4 and Fe3O4/Cs (4:2) are 3.4 and 3.0 eV, respectively. As the mass of Cs increases, the band gap energy decreases. Under UV light irradiation, 50 mg of Fe3O4 and Fe3O4/Cs were analyzed on 7 ppm of methylene blue, pH = 4. The maximum photocatalytic activity Fe3O4/Cs (4:3), achieved an impressive degradation rate of 94.7 % after 120 min of irradiation. The magnetically separable capability means nanocomposites can be recycled and reused five times with high degradation. Furthermore, Fe3O4/Cs has the potential to be a low-cost and environmentally friendly reusable photocatalyst for rapid wastewater degradation.