Exploration of polyelectrolyte incorporated with Triton-X 114 surfactant based osmotic agent for forward osmosis desalination

Selection of a proper osmotic agent is important to make the forward osmosis (FO) feasible. The objective of this study was to enhance FO by lowering reverse solute flux and maintaining high water flux. Poly(propylene glycol) with molecular weight of 725 Da (PPG-725) was found to possess high osmolality, making it a strong candidate for using as a draw agent. In addition, to reduce the partial leakage of draw solute, a non-ionic surfactant (Triton X-114) has been incorporated. Typically, when the hydrophobic tails of Triton X-114 interacted with the membrane surface, a layer on the surface of membrane is produced to constrict the pores and thus minimize the reverse solute flux. In this study, different concentrations of PPG-725 incorporated with different concentrations of Triton X-114 (0.2–0.8 mM) were used to evaluate their osmotic potentials as draw solute. The specific reverse solute flux (J_s/J_w) of 40% PPG-725 doped with Triton X-114 was found to be 0.01 g/L, considerably much lesser than the conventional inorganic draw agents. Finally, membrane distillation operation was utilized as the recovery system in which solute rejection of 97% was achieved for 40% PPG-725/Triton X-114. Therefore, the overall performance supported PPG-725/Triton X-114 as being an efficient draw agent for forward osmosis-membrane distillation hybrid process.