Thermosensitive magnetic ionic liquids with different heterocyclic moieties as draw solutes for forward osmosis

Abstract

Thermosensitive magnetic ionic liquids (TMILs) with different heterocyclic rings, 1-butyl-3-methylimidazolium tetrachloroferrate ([BIM][FeCl4]), 1-butylpyridinium tetrachloroferrate ([BPY][FeCl4]), and 1-butyl-1-methylpyrrolidinium tetrachloroferrate ([BMP][FeCl4]), were synthesized and applied as effective draw solutes in forward osmosis (FO). These heterocyclic-based TMILs exhibited lower critical solution temperatures (LCST) and paramagnetic behaviors, contributing to their use as draw solutes by minimizing energy consumption during solute recovery. The LCSTs of 20 wt% [BIM][FeCl4], [BPY][FeCl4], and [BMP][FeCl4] aqueous solutions were approximately 77, 77, and 69 °C, respectively. Their magnetic susceptibilities at 300 K were 4.283, 4.309, and 4.294 emu g−1, respectively. The water flux of 20 wt% [BMP][FeCl4] was approximately 20.07 Lm−2 h−1 using the active layer-facing draw solution mode. Moreover, [BMP][FeCl4] generated a meaningful water flux against simulated brackish water (2000 ppm NaCl). Thus, the draw solute properties of TMILs containing different ring groups revealed that heterocyclic-based TMILs can be used as potential draw solutes for practical FO systems.