Synthesis and characterization of thin film nanocomposite forward osmosis membranes supported by silica nanoparticle incorporated nanofibrous substrate

One of the critical challenges faced by forward osmosis (FO) is the internal concentration polarization (ICP) during FO process, which can drastically reduce the effective osmotic driving force. In this work, silica nanoparticles were embedded in polyetherimide (PEI) nanofibrous support for making thin film nanocomposite (TFN) polyamide FO membranes to mitigate undesired ICP. The experimental results show that the pore size and porosity of the FO membrane substrate was significantly increased due to silica incorporation; the reason could be mainly attributed to the better heat-press resistance of the silica based nanofibrous substrates, leading to less substrate compaction and porosity reduction during the heat-press treatment. The FO membranes supported with such substrates demonstrated higher osmotic water flux, likely arising from the reduced structural parameter of the support layer. The current work showed that the FO membrane with the highest silica loading of 1.6 wt% in dope solution had the maximum substrate porosity (83%), the smallest structural parameter (~ 174 μm), and the most promising water flux, i.e., 42 L/m2 h in the active layer facing the feed water orientation and 72 L/m2 h in the active layer facing the draw solution orientation when 1.0 M NaCl draw solution and deionised feed water were applied.