Commercial thermo-responsive polyalkylene glycols as draw agents in forward osmosis

Forward osmosis (FO) is a promising technology for efficient water reclamation at low operating costs. It has shown potential in producing fresh water from seawater; however, the regeneration of the diluted draw solution (DS) still holds back further development. Thermo-responsive polymers, especially polyalkylene glycol (PAG) based copolymers with hydrophilic ethylene oxide and hydrophobic propylene oxide units, have shown suitability as DSs in FO using low-temperature waste heat to regenerate the DS. In this study, we explored five commercially available copolymers: Pluronic (R) PE 6400, Pluronic (R) L-35, Pluronic (R) RPE 1740, Unilube (R) 50 MB26, and Polycerin (R) 55GI-2601 as DSs in a laboratory FO setup, with DI water as the feed solution (FS). The water flux and reverse solute flux varied from 1.5 to 2.0 L & sdot;m- 2 & sdot;h- 1 and from 0.04 to 0.4 g & sdot;m- 2 & sdot;h- 1, respectively. Furthermore, all polymer solutions showed the ability to be recovered and reused using temperatures below 100 degrees C. Therefore, the tested PAGs turned out to be promising as draw solutions for FO systems that utilize low-grade waste heat. The re-usage in FO was shown for regenerated Pluronic (R) L-35 through a three-step experiment where its recovery was 91.1 %, 93.1 %, and 91.9 % for each FO cycle, respectively.