Thermo-sensitive polyelectrolytes as draw solutions in forward osmosis process

• New thermo-sensitive polyelectrolytes were prepared and evaluated as draw solutions for FO.
• Hot ultrafiltration was used as a low-energy method to recover the water from draw agents.
• The ease of water recovery and reuse make the polyelectrolyte a good candidate for FO.

A series of polyelectrolytes were evaluated as draw solutions for the forward osmosis (FO) process. Such polyelectrolytes were synthesized by copolymerization of N-isopropylacrylamide with different amounts of sodium acrylate. These polyelectrolytes were thermo-sensitive and water soluble. Hot ultrafiltration (HUF) operated at 45 °C and 2 bar was used as a low-energy method to recover the water from the polyelectrolyte draw solutions. The results showed that 4%PNIPAM-SA solution worked best among nine polyelectrolytes in the forward osmosis process and HUF process, and its FO water flux was 0.347 LMH while the feed solution was pure water and its water recovery fraction was 65.2%.