Zwitterionic polymers showing upper critical solution temperature behavior as draw solutes for forward osmosis

Abstract

We synthesized the zwitterionic homopolymer polysulfobetaine (PBET), which shows upper critical solution temperature (UCST) characteristics, via free radical polymerization in order to investigate its suitability as a draw solute for the forward osmosis (FO) process. The FO and recovery properties of PBET were systematically investigated. The UCST characteristics of the monomer sulfobetaine (BET) were not confirmed, while the UCST of PBET was confirmed to be approximately 40 °C. This result suggests that PBET can be easily recovered from aqueous solutions by cooling them to below the UCST. In an active layer facing feed solution (AL-FS) system containing 20 wt% PBET at a temperature of 50 °C, the water flux and reverse solute flux of PBET were found to be approximately 3.22 LMH and 0.36 gMH, respectively. Thus, we investigated the suitability of homopolymers having UCST characteristics as draw solutes for the FO process for the first time.