Thin-film nanocomposite membrane with vertically embedded carbon nanotube for forward osmosis

Forward osmosis (FO) for desalination is receiving tremendous attention due to its low energy consumption and simple operation compared to reverse osmosis. Here, we propose a thin-film nanocomposite (TFN) membrane with vertically embedded carbon nanotubes (CNTs) in the active layer to maximize membrane permeability without significantly sacrificing selectivity. We first attempted a spray-assisted electromagnetic field alignment technique to vertically embed CNT in the active layer of the TFN membrane. After vertically embedding the CNT, the developed TFN membrane exhibited 20% increased water flux. When chemical etching of the active layer was further applied, increase in water flux was over 300% (40 LMH). Meanwhile, the increased reverse salt flux was mild most likely due to the steric effect of CNT in the active layer. The developed TFN membrane, thus showed even higher water flux and lower reverse salt flux when compared to recently provided commercial FO membranes. This method is easy to up-scale with a one-step fabrication process, and it is cost-effective due to its simplicity and the low concentration of CNT solution used. Therefore, these findings could contribute to freshwater production using the FO process to overcome global water scarcity.