Abstract Forward osmosis (FO) is a low energy consumption technology of great interest for water desalination. A critical step for making FO practical is selection of proper draw solute suitable to increase the osmotic pressure since the biggest challenge facing the application of FO is the separation of fresh water from the draw solution. Using advances in nanotechnology, hydrophilic magnetic nanoparticles were used as novel draw solutes, thus separating the fresh water from draw solution using magnetic field alone without the need of intensive energy. To test the stability of magnetic nanoparticles (MNPs) suspension, two kinds of magnetic nanoparticles (magnetite Fe304 and jacobsite MnFe2O4) were synthesized. The results showed Fe3O4 is not stable that's why it was ruled out as a potential magnetic material suitable to be applied as draw solution, instead focused studied were carried out with MnFe2O4. Different diameters of MnFe2O4 using various metals and bases concentrations were also synthesized to study the effect of particle sizes on the FO performance. It was shown that the lowest metals concentration (0.05 M Mn * + 0.1 M Fet) and the highest base concentration (4 M NaOH) form the smallest MnFe2O4 particles 25 nm. In addition, MnFe204 functionalized by polyvinyl alcohol (PVA), tri-sodium citrate (TSC) and polyethylene glycol (PEG) were synthesized to explore the correlation between surface chemistry of and the achieved osmolality. The results showed the highest water flux performance ~ 10 L/m h was achieved when 2M and 28.6 % organic content of TSC used to functionalize MnFe2O4 MNPs and use it as draw solute in FO application. It is demonstrated that the engineering of surface hydrophilicity and magnetic nanoparticle size are both crucial in their application as draw solutes in FO. Magnetic nanoparticles were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Thermo-gravimetric analysis (TGA), Fourier transform infrared radiation (FTIR), Raman spectrometer, Vibrating sample magnetometer (VSM) and zeta potential. It is believed that magnetic nanoparticles will soon find great use in this area.