Preparation of MAPTES-Fe_3O_4 and its recycling draw agent in forward osmosis

Silane coupling agent with a carboxylic acid end functional group was prepared by amidation of maleic anhydride with aminopropyltriethoxysilane.Superparamagnetic iron oxide nanoparticles(SPIONs) were prepared by chemical co-precipitation method and coated with carboxylic acid on the nanoparticle surface.The modified SPIONs were analyzed by the scanning electron microscope(SEM),Fourier transform infrared spectroscope(FT-IR),vibrating sample magnetometer(VSM),and thermo gravimetric analyzer(TGA).The SPIONs showed the saturation magnetization was 44.4 emu/g and it was easily recovered by the application of an external magnetic field.The nanoparticles were used as draw agent in a forward osmosis process after turning into the sodium form with a water flux of 2.0 L/(m2·h) at the draw solution concentration of 8.1% using a commercial RO membrane.