Preparation of novel magnetic nanoparticles as draw solutes in forward osmosis desalination

Abstract Novel magnetic nanoparticles (MNPs), Fe3O4@SiO2 and Fe3O4@SiO2@PEG-(COOH)2, were prepared by loading different amounts of SiO2 or/and PEG-(COOH)2 onto Fe3O4 nanoparticles, and their feasibility to be used as forward osmosis (FO) draw solutes was investigated. The characterization of the materials showed that, compared to normal Fe3O4 nanoparticles, the modified MNPs exhibited enhanced dispersity and high osmotic pressure in aqueous solution. The FO experiment indicated that the synthesized draw solutes could obtain a water flux as high as 10 L∙m–2·h–1 with an aquaporin FO membrane. The optimal concentration of the added tetraethyl orthosilicate was 30% during the synthesis. The novel MNPs could be easily recovered from draw solutions by magnetic field, and the recovery rate of Fe3O4@SiO2 and Fe3O4@SiO2@PEG-(COOH)2 was 83.95% and 63.37%, respectively. Moreover, after 5 recycles of reuse, the water flux of Fe3O4@SiO2 and Fe3O4@SiO2@PEG-(COOH)2 as draw solutes still remained 64.36% and 85.26%, respectively. The experimental results demonstrated that the synthesized core–shell magnetic nanoparticles are promising draw solutes, and the Fe3O4@SiO2@PEG-(COOH)2 was more suitable to be used as draw solute in FO process.