Performance evaluation of electric-responsive hydrogels as draw agent in forward osmosis desalination

Forward osmosis (FO) has gained more attentions because it has the potential to be an emerging desalination technology. Stimuli-responsive hydrogels, as a novel class of FO draw agent, can completely avoid reverse solute diffusion and release water easily under external stimuli. In this study, 2-Acrylamido-2-methyl-1-propane-sulfonic acid (AMPS) and 2-(Dimethylamino)ethyl methacrylate (DMAEMA) monomers are used to prepare a series of electric-responsive AMPS/DMAEMA hydrogels by aqueous solution polymerization. These hydrogels are adopted as draw agent, by using 2000 ppm NaCl solution as the feed, A0.55D0.45 and A0.53D0.47 hydrogel show better initial water fluxes which are 2.09 and 1.63 LMH, separately. And A0.55D0.45 hydrogel produces 16.12 L.m(-2) total water flux and 0.67 average 24 h water flux. These hydrogels are dehydrated under 15 V electric stimuli. After the first regeneration, their corresponding water recovery rates are 67.45% and 39.36%, separately. After the second regeneration, their initial water fluxes are still recorded at 1.54 and 1.08 LMH, respectively. In contrast with other published literatures, the water flux produced by as-prepared hydrogels has increased significantly. Moreover, using an external electric field to achieve regeneration can simplify the operation of forward osmosis process.