Hydrophilic Superparamagnetic Nanoparticles: Synthesis, Characterization and Application in Forward Osmosis Processes

*Corresponding author, Email: chencts@nus.edu.sg, Fax: (65)-6779 1936 ABSTRACT Freshwater shortage has caused serious world-wide problems and many technologies have been developed for water recycle and seawater desalination. Forward osmosis (FO) as a promising technology has attracted much attention, but the exploration of highly hydrophilic and easily separable draw solutes with high osmotic pressures makes this technology full of challenge. Superparamagnetic nanoparticles are materials consisting of a magnetic core and polymer shell. The magnetic core contains small magnetic nanoparticles and can be separated from mixtures under an external magnetic field. The polymer shell surrounds the magnetic core to prevent particle aggregation and also enables modification. MNPs can be purposely designed and synthesized for specific applications. Such characteristics make magnetic nanoparticles an appropriate option of being draw solutes. In this work, we have synthesized a series of hydrophilic magnetic nanoparticles (MNPs), investigated their potential as draw solutes in FO systems, and explored their recovery and reusability. Good water fluxes are achieved in FO processes. The MNPs can be easily recovered from draw solutions by the magnetic field and reused. Results have demonstrated that using PEG based MNPs as draw solutes is a feasible way in the FO process.