Synthesis of spherical Fe3O4 magnetic nanoparticles by co-precipitation in choline chloride/urea deep eutectic solvent

Abstract Fe 3 O 4 nanoparticles have been widely explored in magnetic separation, and are usually made in water or organic solvents. In this work, spherical Fe 3 O 4 -DES magnetic nanoparticles of ca. 10.5 nm were prepared by co-precipitating Fe 3+ and Fe 2+ ions in ionic solvent comprising choline chloride/urea deep eutectic mixture for the first time. Upon surface modification by ethylenediamine tetraacetate (EDTA), the Fe 3 O 4 -DES/EDTA magnetic nano-adsorbent has significantly improved Cu 2+ adsorption capacity than Fe 3 O 4 -DW/EDTA (28 vs. 21 mg/gFe 3 O 4 ), where Fe 3 O 4 -DW is synthesized in water under otherwise identical conditions.