Efficient heavy metal removal by thin film nanocomposite forward osmosis membrane modified with geometrically different bimetallic oxide

A novel thin film nanocomposite (TFN) forward osmosis (FO) membrane with a positively charged and nano functional substrate layer has been developed for effective heavy metal ions removal. The substrate layer is constructed by adding titania nanotubes and magnetite oxide hybrid nanoparticles (TNT-Fe3O4) in the polysulfone (PSf) matrix. The introduction of nanoparticles endowed the substrate layer with improved hydrophilicity and loose structure. The modified substrate layer also improved the affinity between the nanofillers and polymer matrix, hence maintaining the selectivity of membrane. Compared to pristine thin film composite (TFC) membrane, the TFN with 0.5 wt.% nanofillers loading showed enhanced water flux from 1.63 to 2.82 L m(2) h(-1) without losing its selectivity in terms of Js/Jv ratio when operated in FO mode. The enhancement was mainly attributed to the improved substrate hydrophilicity which has effectively reduced the internal polarization concentration (ICP). The best performing TFN-0.5 membrane increased the water flux with 73% compared to TFC and exhibited a high Cd2+ and Pb2+ heavy metal ion rejection of >98%. By designing the substrate layer, this study demonstrated the feasibility of enhancing the performance of FO membrane for treating heavy metal wastewater through a simple and efficient method.