Photocatalytic Reduction of Aqueous Hexavalent Chromium Using Novel Green-Synthesized Magnetite/Chitosan Nanocomposites employing Moringa Oleifera Leaf Extract under UV Irradiation

Abstract

The utilization of green synthesized magnetite/chitosan (Fe₃O₄/[C₆H₁₁NO₄]_n(Cs)) nanocomposites catalyst, derived from moringa oleifera (MO) leaf extract, exhibited remarkable efficacy in the UV-induced catalytic transformation of dissolved hexavalent chromium (Cr (VI)). Structural analysis via X-ray diffraction revealed an inverse spinel cubic configuration, while transmission electron microscopy indicated quasi-spherical, heterogeneous morphology. Fourier transform infrared spectroscopy disclosed the existence of characteristic functional groups including metal-oxygen bonds, hydroxyl groups, aliphatic carbon-hydrogen stretches, and various carbon-oxygen linkages, as well as primary amine functionalities. This spectral profile provides evidence for the successful integration of Fe₃O₄ nanoparticles within the Cs. Elemental composition analysis was carried out using energy dispersive X-ray analysis along with scanning electron microscope imaging techniques, resulting in a quantitative assessment of the constituent elements. The unmodified Fe₃O₄ nanoparticles exhibited a composition of 70.9 % iron (Fe) and 29.1 % oxygen (O), while the Cs functionalized Fe₃O₄ nanocomposites demonstrated a more complex elemental distribution: 47.9 % of Fe, 36.4 % of O, 11.3 % of carbon (C), and 4.4 % of nitrogen (N). Magnetic properties assessed through vibrating sample magnetometer and the saturation magnetization of Fe₃O₄, Fe₃O₄/Cs (4:2), and Fe₃O₄/Cs (4:4) are 54.2, 42.0 and 28.0 emu/g, respectively. Ultraviolet-visible spectrophotometer revealed absorption peaks between 365 and 377 nm, with a band gap energy in the interval 2.88–3.00 eV Optimal photocatalytic reduction of Cr(VI) performance was achieved with the composition Fe₃O₄/Cs (4:4) nanocomposites, with an outcome reduction of Cr(VI) of a 76.7 % rate in two hours of irradiation. The characteristics magnetic character of these nanocomposites promotes favorable separation and reuse up to three cycles, enhancing the economic growth and practical application of this wastewater treatment approach. In conclusion the synthesizing of environmentally beneficial Fe₃O₄/Cs nanocomposites is also a promising solution for remediation of Cr(VI) contaminants that is also efficient and sustainable in aqueous environments.