Nanomaterials, including nanoparticles such as iron oxide nanoparticles, have received great attention from researchers due to their unique properties and applications. There are several diverse methods, including chemical, physical, and green biological methods, to prepare iron oxide nanoparticles. The green method was chosen because it is safer, purer, and less toxic compared to other methods. Therefore, the green method is a promising and environmentally friendly method in the near future. The aqueous extract of Iraqi orange leaves was used to prepare nano iron oxide, it was examined structurally and spectrally by several techniques (X-ray diffraction- XRD, Fourier transform infrared - FT-IR, field emission scanning electron microscopy - FESEM, energy disperse X-ray spectroscopy - EDX, and UV-vis spectroscopy). Through the diagnosis, it was proven that the nano iron oxide was successfully prepared in a spherical form with an average size equal to 68.5 nm. The nano iron oxide particles were tested to remove the crystal dye from its aqueous solution, where the removal percentage reached 61% at 298K, dose adsorbent = 0.01 g, contact time = 90 min, and initial concentration = 11 mg/L. This indicates the possibility of using nano iron oxide which preparing by green method in the field of water treatment. Keywords: Fe3O4 NPs, green method, orange leaf aqueous extract, adsorption, crystal violet dye.
