Hydrophilic and Compressible Aerogel: A Novel Draw Agent in Forward Osmosis

Forward osmosis (FO) technology is an efficient route to obtain purity water for drinking from wastewater or seawater. However, there are some challenges in draw solution to limit its application. We first introduce a novel sodium alginate-graphene oxide (SA-GO) aerogel as draw agent for highly efficient FO process. The GO nanosheets covalently cross-linked to SA matrix to form a three-dimensional and highly porous aerogel to provide excellent water flux and operation stability, together with the property of compressibility served by SA-GO aerogel resulting in easy water production and regeneration process. When deionized water was used as the feed solution, the SA-GO aerogel exhibited a higher water flux (15.25 ± 0.65 L m^-2 h^-1, abbreviated as LMH) than that of 1 mol L^-1 NaCl (1 M), and there was no nonreverse osmosis phenomenon. The water fluxes were stabilized in the range of 5-6.5 LMH during recycle process of absorbing and releasing water as high as 100 times. It also had a great desalination capacity (water flux was 7.49 ± 0.61 LMH) with the seawater (Huanghai coast) as the feed solution. Moreover, the water production and regeneration process of the SA-GO aerogel can be rapidly and cost-effectively accomplished with low-strength mechanical compression (merely 1 kPa). The results present that the SA-GO aerogels as a promising, innovative draw agent can make the FO process simpler, more efficient, and lower energy consumption. It can be a potential material for hydration bags to fast and repeatable product fresh water from saline water or wastewater.