Highly efficient degradation of basic dyes using gold-coated nature-based supermagnetic iron oxide nanoparticles as eco-friendly nanocatalysts

Nowadays, organic dyes are prevalent components in wastewater discharges due to their extensive use in various industries, posing a significant threat to public health across different organisms. As a result, wastewater treatment has become an indispensable requirement. In this study, we synthesized supermagnetic iron oxide (Fe₃O₄ NPs) and gold-iron oxide bimetallic nanoparticles (Au@Fe₃O₄ BNPs) using an eco-friendly method that involved natural compounds extracted from brown Egyptian propolis. We employed UV-visible spectroscopy, FTIR, XRD, VSM, SEM, HRTEM, EDX, Zeta potential and XPS techniques to examine the optical characteristics, chemical structure, crystalline structure, magnetic properties, morphology, size, and chemical composition of these biosynthesized nanoparticles. Furthermore, these nanoparticles were used as nanocatalysts for the removal of cationic dyes. The photocatalytic results indicated high efficiency in the removal of methylene blue (MB), crystal violet (CV), and malachite green (MG) dyes from aqueous solutions using Fe₃O₄ NPs and Au@Fe₃O₄ BNPs. The removal rates of MB, CV, and MG were about 95.2% in 70 min, 99.4% in 50 min, and 96.2% in 60 min for Fe₃O₄ NPs, and 97.1% in 50 min, 99.1% in 30 min, and 98.1% in 50 min for Au@Fe₃O₄ BNPs, respectively. The study also assessed the potential anti-radical properties of the extract, Fe₃O₄ NPs, and Au@Fe₃O₄ BNPs using the DPPH assay, and the results demonstrated their antioxidant activity. Finally, these Fe₃O₄ NPs and Au@Fe₃O₄ BNPs have the potential to serve as efficient antioxidants and photocatalysts for removing basic dyes from water.