Impact of nanoparticles surface characteristics on pore structure and performance of forward osmosis membranes

Abstract

Forward osmosis is a new emerging technology which has shown great potential in low cost and highly efficient water desalination. The major obstacle in further development of forward osmosis processes is internal concentration polarization which can significantly lower the water flux through the membranes. Herein, in order to increase the membrane hydrophilicity and thus, reduce the internal concentration polarization, polyethersulfone was selected as an efficient support layer and treated with nanoparticles of different surface characteristics. To fabricate such modified membranes, ZnO and stable ZnO-SiO2 core-shell nanoparticles were dispersed within the polyethersulfone solution and subsequently, a thin active layer of polyamide was deposited on the obtained support layers by using interfacial polymerization method. Morphological characterizations revealed the major impact that nanoparticles surface properties had on cross-section pores structure which were formed within polyethersulfone support layers. The sponge like pores within the membrane support layers were changed from loose to long finger like structures when the polyethersulfone was chemically modified by ZnO and ZnO-SiO2 core-shell nanoparticles, respectively. Moreover, permeate flux enhancements as high as 117% were observed in the membranes modified by ZnO-SiO2 core-shell nanoparticles. This implied that such nanoparticles could be a promising candidate to improve the performance of forward osmosis membranes.