Minimizing structural parameter of thin film composite forward osmosis membranes using polysulfone/halloysite nanotubes as membrane substrates

Novel forward osmosis (FO) is a membrane-based separation process with significant potentials for low energy desalination. While this technology offers various benefits, overcoming its low water flux performance caused by internal concentration polarization (ICP) of solutes in porous substrates remains a challenge. This study aims at addressing this issue by introducing hydrophilic halloysite nanotubes (HNTs) into substrate made of polysulfone (PSF). The thin film nanocomposite (TFN) membranes suitable for FO applications were prepared via interfacial polymerization on the top surface of PSF-HNT nanocomposite substrates. The results obtained from filtration experiments showed that the TFN membrane prepared with 0.5 wt% HNTs (TFN0.5 membrane) demonstrated the most satisfactory results by exhibiting high water permeability and low reverse solute flux. Furthermore, TFN0.5 membrane exhibited remarkably higher water flux than that of control TFC membrane in both FO (27.7 vs 13.3 L/m2 h) and PRO (42.3 vs 26.0 L/m2 h) configurations when they were tested with 10 mM NaCl as feed solution and 2 M NaCl as draw solution. This improvement can be ascribed to the fact that the structural parameter of TFN0.5 is much lower compared to control TFC membrane (0.37 vs 0.95 mm), leading to reduced ICP effect.