Facile synthesis of N-(aminoethyl)-aminopropyl functionalized core-shell magnetic nanoparticles for emulsified oil-water separation

In this study, a class of N-(aminoethyl)-aminopropyl functionalized core-shell magnetic nanoparticles (MNPs) was fabricated for emulsified oil-water separation. Fe3O4 MNPs were synthesized by using a solvothermal method, followed by surface coating with N-(aminoethyl)-aminopropyl functionalized silica (AEAPFS) layer to improve its chemical stability, surface charge and interfacial activity. The synthesized MNPs were characterized by various technologies and their oil-water separation performances were evaluated under various conditions. Although Fe3O4 MNPs had negligible oil separation efficiency, the AEAPFS-coated MNPs (Fe3O4@AEAPFS MNPs) exhibited satisfactory oil-water separation performance at various pH levels. Results showed that, under both acidic and neutral conditions, positively charged Fe3O4@AEAPFS MNPs could effectively adsorb onto oil droplets via electrostatic attraction and interfacial activity; while under alkaline condition, negatively charged MNPs could overcome electrostatic repulsion and absorb onto oil droplet via hydrophobic interaction, thereby facilitating subsequent magnetic separation. Moreover, the synthesized Fe3O4@AEAPFS MNPs could be recycled up to 5 cycles without showing significant loss in separation efficiency. In conclusion, Fe3O4@AEAPFS MNPs can be easily synthesized and recycled, providing a simple but powerful approach for emulsified oil-water separation.