Synthesis of superparamagnetic Fe3O4 nanoparticles coated with green tea polyphenols and their use for removal of dye pollutant from aqueous solution

Superparamagnetic Fe3O4 nanoparticles coated with Green Tea Polyophenols (GTP), i.e. Fe3O4@GTPs NPs were synthesized by wet-chemical method with eco-friendly and environmentally benign approach. The coated NPs were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectroscopy (EDS). These analyses revealed that the particles were of uniform shapes and sizes of 10 +/- 3 nm with a coating of GTPs. The vibrating-sample magnetometer (VSM) measurement of the coated sample demonstrated a saturation magnetization of 61 emu/g with negligible coercivity (similar to 0.001 T) and retentivity (similar to 0.9 emu/g) indicating superparamagnetic behavior the NPs at room temperature. The synthesized NPs were highly stable and well-dispersed in aqueous medium through their hydrophilic coating of GTPs. These particles showed high adsorption capacity (7.25 mg/g) for removal of methylene blue (MB) dye in wastewater treatment. The sorption dynamic and equilibrium data were in good agreement with the pseudo-second-order kinetic and Langmuir isotherm models respectively. In addition, the particles could be easily separated from the liquid medium through magnetic separation and potentially reused in multiple cycles.