Eco-friendly magnetic silk fibroin films for heavy metal adsorption in water purification

Silk magnetic nanocomposite films (SMNCs) were prepared by casting silk fibroin (SF) with iron oxide (Fe 3 O 4 ) nanoparticles (NPs) in solution. Ultraviolet visible (UV Vis) spectroscopy confirmed the surface plasmon resonance (SPR) of the produced magnetic nanocomposites, while Fourier-transform infrared (FT-IR) analysis showed a decrease in β-sheet content and an increase in amorphous regions with higher Fe 3 O 4 loading. X-ray diffraction (XRD) analysis revealed the nanostructural characteristics of Fe 3 O 4 nanoparticles embedded in the SF matrix. Scanning electron microscopy (SEM) showed spherical nanoparticles, and energy-dispersive X-ray spectroscopy (EDS) confirmed iron incorporation. A vibrating sample magnetometer (VSM) demonstrated a saturation magnetization of 45 emu/g and coercivity of 60 Oe in the sample with the highest Fe 3 O 4 content. Thermogravimetric analysis (TGA) indicated improved thermal stability with increasing Fe 3 O 4 concentration. The nanocomposites showed high adsorption capacity of 130 mg/g for Ni 2+ ions in aqueous solution, with adsorption following pseudo-second-order kinetics (R 2 =0.998). The films exhibited tunable magnetic properties and efficient metal ion removal. Our findings highlight a green and efficient method for creating silk-based magnetic nanocomposites that combine eco-friendly synthesis with excellent adsorption performance, supporting their applicability in sustainable water treatment solutions. • Developed nanocomposite films of silk magnetic (SF-Fe 3 O 4 ) with varying weights percentages. • The highest Fe 3 O 4 (wt%) loaded sample had 45 emu/g saturation magnetization and 60 Oe coercivity. • The study discovered that SF can be converted from diamagnetism to ferromagnetism. • The nanocomposite adsorbs heavy metal nickel at a rate of approximately 130 mg/g. • Magnetic silk fibroin thin films effectively remove heavy metals from aqueous solutions.