Thermo-responsive oligomeric poly(tetrabutylphosphonium styrenesulfonate)s as draw solutes for forward osmosis (FO) applications

Abstract A series of oligomeric poly(tetrabutylphosphonium styrenesulfonate)s (PSSP#, where # is the number of monomer units in the oligomer) were prepared from tetrabutylphosphonium styrenesulfonate (SSP) as a monomer for application as a draw solute in a forward osmosis (FO) system. Although the water permeation flux values in the FO system using the oligomeric PSSP as a draw solute were slightly smaller than those using the monomeric SSP, the reverse solute flux values using the PSSPs were found to be much smaller than those using the SSP, indicating that the oligomers are more efficient draw solute materials in the FO system than the low molecular weight monomer. For example, when 20 wt.% of the PSSP5 aqueous solution is used as the draw solution, the water permeation flux and reverse solute flux values are 14.50 LMH and 0.14 gMH, respectively, and when 20 wt.% of the SSP aqueous solution is used, they are 16.28 LMH and 0.53 gMH, respectively. Since PSSPs have a lower critical solution temperature (LCST), the PSSP in water could be simply separated by heating to above the LCST without any other separation process. Moreover, it was found that the PSSPs have excellent bactericidal property above 99.9% against Escherichia coli (ATCC 8739).