Ultrahigh Dispersion of Fe₃O₄ NPs on Cellulose Nanofibers: Unlocking Superior Visible-Light Photocatalysis

Constructing cost-effective and efficient photocatalysts is crucial for removing harmful contaminants from water sources, ensuring a greener and healthier environment. In this study, highly dispersed magnetic iron oxide (Fe₃O₄) nanoparticles (NPs) were successfully decorated on cellulose nanofibers (CNFs) by using a simple interfacial strategy. Four hybrid materials (Fe₃O₄-CNF1, Fe₃O₄-CNF2, Fe₃O₄-CNF3, and Fe₃O₄-CNF4) were systematically synthesized, with Fe₃O₄-CNF4 identified as the most efficient photocatalyst. The optimized Fe₃O₄-CNF4 hybrid exhibited a high surface area (54.12 m²/g), enhanced light utilization, and improved charge separation, leading to superior photocatalytic performance. It achieved a 95% removal rate of Rhodamine B (RhB) in 120 min and 99% removal rate of Methylene Blue (MB) in 150 min when exposed to visible irradiation. Moreover, Fe₃O₄-CNF4 demonstrated excellent recyclability, maintaining high efficiency over five reuse cycles with only ∼7% activity loss. Stability tests under varying catalyst concentrations and pH conditions further confirmed its robustness. Additionally, the primary active species, potential degradation pathways of MB, and the underlying reaction mechanism were systematically analyzed. These findings highlight Fe₃O₄-CNF4 as a promising visible-light-responsive and reusable photocatalyst for wastewater treatment.