posted on 2016-01-19, 00:00authored byYujiang 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.