Fabrication and comparison of RO-like and NF-like forward osmosis membranes

Abstract

Forward Osmosis (FO) technology is becoming popular due to its potential applications in many important fields and its numerous advantages. As such, there is a demand for high-performance FO membranes (i.e. high water permeability, A and low salt permeability, B). A few RO-like and NF-like membranes have been developed in literature and demonstrated good FO performance. Complicated influences of membrane properties on FO performance, depending on operational conditions were discussed in this study. To meet future FO applications, systematic comparison is necessary.

Thin film composite (TFC) membranes with tailored rejection layer were fabricated in the current study. Two types of high-performance FO membranes were prepared, by two steps. The resultant RO-like and NF-like FO membranes were tested and investigated on its performance and effect of separation properties on FO performance. The relationship of FO water flux between both the membrane water permeability and its salt rejection was demonstrated in the current study. While both membranes displayed good rejection with divalent ion solution, NF-like FO membrane had poor monovalent NaCl salt retention. Analysis from FO tests results also highlights NF-like FO membrane excellent FO performance with divalent ion draw solution. This study suggests that membrane optimization would allow better and efficient performance with different FO applications.