POSS-containing delamination-free dual-layer hollow fiber membranes for forward osmosis and osmotic power generation

Novel mixed matrix hollow fiber membranes composed of a PBI/POSS outer layer and a PAN/PVP inner layer have been developed for forward osmosis and osmotic power generation. It is found that the incorporation of a small amount of POSS nanoparticles into the outer PBI dope has significant influence on both the morphology and the performance of the developed membranes. The addition of POSS and PVP into the outer PBI and inner PAN dopes respectively resulted in an integrally macrovoid-free and delamination-free dual-layer membrane. Increasing POSS concentration in the PBI dope enhances both water and salt permeability across the membranes. A POSS loading of 0.5 wt% has been identified through NF and FO tests as the optimal concentration in this study. The membrane with this optimized concentration shows a maximum water flux 31.37 LMH at room temperature using 2.0 M MgCl2 as the draw solution in the FO process and a maximum power density of 2.47 W/m2 in the PRO process at 7 bar using 1.0 M NaCl as the draw solution. With its unique fully hydrophilic structure, easy processability and cost-effective ultra-thin PBI outer-layer, this membrane may have wide applications in the future.