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Using UCST Ionic Liquid as a Draw Solute in Forward Osmosis to Treat High-Salinity Water

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journal contribution
posted on 19.01.2016, 00:00 authored by Yujiang Zhong, Xiaoshuang Feng, Wei Chen, Xinbo Wang, Kuo-Wei Huang, Yves Gnanou, Zhiping Lai
The concept of using a thermoresponsive ionic liquid (IL) with an upper critical solution temperature (UCST) as a draw solute in forward osmosis (FO) was successfully demonstrated here experimentally. A 3.2 M solution of protonated betaine bis­(trifluoromethylsulfonyl)­imide ([Hbet]­[Tf2N]) was obtained by heating and maintaining the temperature above 56 °C. This solution successfully drew water from high-salinity water up to 3.0 M through FO. When the IL solution cooled to room temperature, it spontaneously separated into a water-rich phase and an IL-rich phase: the water-rich phase was the produced water that contained a low IL concentration, and the IL-rich phase could be used directly as the draw solution in the next cycle of the FO process. The thermal stability, thermal-responsive solubility, and UV–vis absorption spectra of the IL were also studied in detail.