A study of water permeation using glycerol as the draw solution with thin film composite membranes in forward osmosis and pressure retarded osmosis configurations

In this work, three different types of commercial thin film composite (TFC) membranes were selected to conduct the study. They were TFC-HR, ACM5 and Aquaporin (AQP) membranes. Water permeation fluxes of these membranes were accessed under forward osmosis (FO) and pressure retarded osmosis (PRO) configurations with deionized (DI) water as the feed. For the draw solutions, glycerol and sodium chloride (NaCl) solutions with concentrations ranged from 1 to 100 wt% and 1 to 25 wt%, respectively were utilized. In general, the water permeation performance study revealed that the PRO configuration delivered higher water fluxes for both glycerol and NaCl, irrespective of the membranes and concentration of the draw solutions used. In comparison between glycerol and NaCl at 20 wt%, NaCl exhibited 185 % and 174 % better water flux in FO and PRO configurations, correspondingly with the AQP membrane. This study disclosed that when a draw solution of lower osmotic pressure such as glycerol is used, the usage of membrane with higher porosity and hydrophilicity can improve the water flux.