Novel thin-film composite reverse osmosis membrane with superior water flux using parallel magnetic field induced magnetic multi-walled carbon nanotubes

Abstract In this work, magnetic multi-walled carbon nanotubes (MWCNTs) were aligned vertically in thin film nanocomposite (TFN) reverse osmosis (RO) membranes. Magnetic MWCNTs were synthesized by in situ co-precipitation of MWCNTs, Fe2+ and Fe3+. Meanwhile, a parallel magnetic field created by two ferrite magnets was used to align magnetic MWCNTs. To simulate the magnetic field, the computer software COMSOL-Multiphysics® was applied. In order to demonstrate the impact of parallel magnetic field, two groups of TFN RO membranes (Group A and Group B) were prepared. Before the phase inversion process, polymer solutions of Group A were treated in the parallel magnetic field for 2 min, while polymer solutions of Group B were exposed to air for 2 min. As a result, under magnetic field, magnetic MWCNTs were aligned vertically on the polysulfone surface, and provided efficient water transport channels. The optimized membrane with 0.7 wt% magnetic MWCNTs of Group A obtained remarkable water flux of 11.389 L m−2 h−1 while maintaining high NaCl rejection. The results indicated that a simple and efficient method to improve water flux of TFN RO membranes was successfully developed.