Graphene oxide/alginate/polyacrylate hydrogels as a draw agent for osmosis water purification

Abstract

Alginate–polyacrylate hydrogels (A-PAA) and graphene oxide-incorporated alginate–polyacrylate (A-PAA-GO) hydrogels were synthesized and found to possess permanent self-generating osmotic potential – the hydrogels showed the ability to continuously draw water across an osmotic membrane. Dynamic water contact angle tests demonstrated that the surfaces of A-PAA and A-PAA-GO were superhydrophilic. Water production studies demonstrated that the hydrogels were able to successfully draw water across an osmotic cellulose triacetate membrane continuously; short-term and long-term preliminary tests showed that the water production of A-PAA-GO was 140.9% (10.6 ± 1.5 g) and 86.9% (53.2 g) higher than that of A-PAA, respectively. In organics removal tests, the water production of A-PAA-GO was 21.9 g with a 93% humic acid rejection, whereas that of A-PAA was 16.6 g with a 94% humic acid rejection. The superior water production of A-PAA-GO was due to a combined result of the osmotic potential-inducing PAA and the flexible GO nanosheets, both of which helped produce more hydrophilic sites and improve the interconnectivity of the hydrophilic channels within the hydrogel matrix. Furthermore, it was found that water was collected directly without the use of external stimuli. The A-PAA-GO hydrogels demonstrated promising potential for use as non-liquid draw agents in osmosis water purification and production.