In-situ coating of Fe-TA complex on thin-film composite membranes for improved water permeance in reverse osmosis desalination

Post-modifications of thin-film composite (TFC) reverse osmosis (RO) membranes have been extensively studied to improve the overall separation performance. However, new approaches have yet to be explored not only to achieve better separation efficiency, but also to reduce the overall manufacturing cost. In this work, a ferric -tannic acid (Fe-TA) complex is post-coated onto the bare TFC membranes in an in-situ stepwise process. By optimizing the concentrations of Fe3+ and TA, the resulting membrane can achieve a water permeance of 3.58 L m- 2 h-1 bar- 1 (LMH bar -1) and a salt rejection of 98.37 % at 20 bar for brackish water desalination, owing to the improved surface hydrophilicity, roughness and additional water pathways. Moreover, the optimal mem-brane also exhibits comparable performance in seawater desalination and boron removal. This new approach of modification shows potentials to be integrated into the current roll-to-roll membrane fabrication process.