Forward osmosis desalination using polymer hydrogels as a draw agent: Influence of draw agent, feed solution and membrane on process performance

We have previously reported the use of hydrogel particles as the draw agent for forward osmosis desalination. In the present work, the effects of draw agent, feed concentration and membrane on the process performance were systematically examined. Our results showed that the incorporation of carbon filler particles in polymer hydrogels led to enhanced swelling ratios of the draw agents and thus higher water fluxes in the FO process. The composite polymer hydrogel particles of sizes ranging from 100 μm to 200 μm as draw agents induced greater water fluxes in FO desalination as compared with those with larger particle sizes (500–700 μm). Similar to other types of draw solutes, as the salt concentration in the feed increased, the water flux created by the polymer hydrogel draw agent decreased; the use of a cellulose triacetate forward osmosis membrane resulted in higher water flux compared with the use of a polyamide composite reverse osmosis membrane.

Polymer hydrogels were studied as a draw agent for forward osmosis (FO) desalination owing to their stimuli responsive properties. The incorporation of carbon particles, hydrogel particle size, feed salt concentration and membrane type were shown to have significant effects on FO water flux.Figure optionsDownload high-quality image (120 K)Download as PowerPoint slideHighlights
► Smaller polymer hydrogel particles led to higher FO water flux.
► The swelling ratio of hydrogels was enhanced by incorporating carbon spheres.
► Higher salt concentration led to lower FO water flux.
► Commercial FO membrane was more suitable than RO membrane.