Thermo-responsive draw solute for forward osmosis process; poly(ionic liquid) having lower critical solution temperature characteristics

RSC Advances Pub Date: 2019-09-18 DOI: 10.1039/C9RA04020J

Abstract

We synthesized poly(4-vinylbenzyltributylammonium hexanesulfonate) (P[VBTBA][HS]), a poly(ionic liquid) that shows lower critical solution temperature (LCST), via the anion exchange reaction of poly(4-vinylbenzyltributylammonium chloride) (P[VBTBA][Cl]) with sodium hexanesulfonate in order to investigate its suitability as a draw solute for the forward osmosis (FO) process. P[VBTBA][Cl] was obtained by the free radical polymerization of (4-vinylbenzyltributylammonium chloride [VBTBA][Cl]) monomer acquired by the Menshutkin reaction. The FO performance and recovery properties of the synthesized materials were systematically investigated. For example, the LCST of P[VBTBA][HS] was observed to be ～17 °C at 20 wt%, while no LCST was observed for [VBTBA][Cl] monomer and P[VBTBA][Cl] polymer before the anion exchange reaction, indicating that P[VBTBA][HS] can be recovered from the aqueous solution by heating it to above its LCST. Moreover, in an active layer facing the feed solution (AL-FS) system containing 20 wt% aqueous P[VBTBA][HS] solution at 15 °C, the water flux and reverse solute flux of P[VBTBA][HS] were found to be ～5.85 L m?2 h?1 and 1.13 g m?2 h?1, respectively. Therefore, we studied the feasibility of using the poly(ionic liquid), a homopolymer having LCST characteristics, as a draw solute in the FO process.

Graphical abstract: Thermo-responsive draw solute for forward osmosis process; poly(ionic liquid) having lower critical solution temperature characteristics
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