Morpholine Derivatives as Thermoresponsive Draw Solutes for Forward Osmosis Desalination

To develop a forward osmosis (FO) process, selection of draw solutes (DSs) is a critical factor in determining water permeability of the process. In this search for novel high-performance DSs, various morpholine derivatives were investigated for their thermoresponsive potential. 4-Butylmorpholine (BuMP) showed a preferable minimum lower critical solution temperature for the FO process (31.7 degrees C). The dilute phase of BuMP after phase separation at 70 degrees C showed a low concentration (3.3 wt %) and low osmotic pressure (3.16 bar). In the FO flux test, the water permeability and reverse solute flux of BuMP (55.0 wt %, 28 bar) against water were J(w) 2.09 L m(-2) h(-1) and J(s) 14.0 g m(-2) h(-1), respectively. Using 0.6 M NaCl (model seawater) as feed solution, BuMP (94.6 wt %) could extract water from this model seawater (J(w) 0.56 L m(-2) h(-1)). These results indicate a high potential for MP derivatives as DSs and provide new guidance for their development for FO desalination.