Effect of polymer substrate on the performance of thin-film composite nanofiltration membranes

Nanofiltration (NF) can be classified as a separation membrane-based process that falls between the standards of ultrafiltration and reverse osmosis processes in the matter of rejected particles size and ionic species. This process could be utilized when a substantial removal of sodium ions is unnecessary, but divalent ions, such as Mg and Ca, elimination is the goal. In this research, thin-film composite (TFC) membranes were prepared on different polymeric substrates, namely: polysulfone (PSU), polyethersulfone, and polyacrylonitrile. Furthermore, their performance for salts removal by the NF was tested. Multiple examination methods were employed to characterize the films and investigate their physicochemical specifications, including scanning electron microscope, atomic force microscopy, and contact angle. Results showed that PSU-supported TFC membranes exhibited the best NF performance in terms of CaCl2 rejection, while all the prepared membranes showed low NaCl salt rejection. These results confirm the nanofiltration nature of the prepared TFC membranes and the impact of the support layers on the TFC performance.