Green Modification of Iron Oxide Nanoparticles with Achillea wilhelmsii and ‎Investigation of Their Performance for Methylene Blue Adsorption

Biosynthesis of nanoparticles (NPs) by plant extracts as a one-pot, cost-effective and rapid method has attracted the great attention due to the controllable properties of nanoparticles. Herein, for the first time we report a method for synthesis of a polyphenol modified magnetically separable Fe3O4 NPs by aqueous extract of Achillea wilhelmsii C. Koch (Aw) leaves as a natural capping and reducing agent for water remediation purposes. Aw is the native plant of Iran with high amount of polyphenol compound that its aqueous leaf extract offers several advantages, including modification of structures and improving the physical and chemical properties of the Fe3O4. The prepared nanoparticles possessed great magnetism (~60), pure crystalline structure, and high adsorption capacity toward cationic dye like methylene blue (MB) (~8 mg/g). The Aw-Fe3O4 nanoparticles displayed pH-responsive behavior. With an increase in pH value, the phenolic compounds were deprotonated and revealed enhanced electrostatic interactions with high MB removal efficiency (73%). The intra-particle diffusion and pseudo-second-order kinetic model were suitable to illustrate the adsorption processes of MB.  Moreover, the obtained nanoparticles showed efficient reusability after three cycles. Altogether, the finding of this study demonstrates that Aw-Fe3O4 NPs can be considered as a suitable adsorbent to purify dye wastewater.