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In forward osmosis (FO) water desalination process, water recovery from diluted draw solute solution is an important issue. In this study, the water recovery characteristics of the thermo-responsive tetrabutylphosphonium hydrogen maleate [[P4444][hydrogen maleate]] ionic liquid draw solute and its lower critical solution temperature (LCST) phase separation type were investigated. Above LCST, the hydrated thermo-responsive ionic liquid draw solute can be dehydrated. In [[P4444][hydrogen maleate]] ionic liquid, it was considered that the dehydrated hydrogen maleate anion can form the intramolecular hydrogen bond, and then macroscopic phase separation was triggered. For water recovery economically, the LCST macroscopic phase separation and two distinct phases should be completed in a definite time. The macroscopic phase separation time to two distinct phases is dependent on temperature and the water content. Shorter time was observed at higher temperature and water content. In FO test with the [[P4444][hydrogen maleate]] draw solute, an average water flux of 3.43 LMH is maintained at 25°C in our experimental condition. The Js/Jw of 2.23 g/L was observed. The technical advantage is that the ionic liquid layer can be directly reused, and the recovery of water is conducted from the water-rich supernatants.

Author：劉柏逸、鐘琍菁、王鈞逸、何佳樺、鄭茲瑀、許皓翔、黃盟舜、梁德明、張敏超、洪仁陽

★Article source：Desalination and Water Treatment