Developing recyclable pH-responsive magnetic nanoparticles for oil-water separation

Hybrid magnetic nanoparticles (MNPs) with well-defined core-shell structure, pH-tunable interfacial activity and strong magnetic responsiveness were developed as recyclable stabilizers for oil-water separation. The Fe3O4 magnetic core was synthesized using a solvothermal method involving hydrolysis of Fe(II) and Fe(III) salts in basic condition, followed by surface-initiated atom transfer radical polymerization (SI-ATRP) of dimethylaminoethyl methacrylate to grow the PDMAEMA shell. The magnetic core allowed rapid separation of the oil droplets from emulsions under external magnetic field, while the pH-responsive polymer shell offered the hybrid MNPs tunable interfacial activity to form and break Pickering emulsion reversibly for recyclable use of the hybrid MNPs. Results showed that MNPs with longer PDMAEMA arms exhibited broader suitable pH range to form Pickering emulsion, but slower magnetic responsiveness. An optimized sample MNP3 with DP of PDMAEMA ca. 65 was screened out and tested to prove efficient separation of diesel emulsion droplets from water and the recyclability of the hybrid MNPs. (C) 2014 Elsevier Ltd. All rights reserved.