Hydrophilic nylon 6,6 nanofibers supported thin film composite membranes for engineered osmosis

Previous studies have concluded that an ideal thin film composite (TFC) membrane specially designed for Engineered Osmosis (EO) should have an ultra-thin selective layer with excellent permselectivity supported by a hydrophilic, highly porous, non-tortuous and thin support structure. In this study, an emerging TFC supporting material, electrospun nanofibers, were used to fabricate a TFC-EO membrane where the support structure and the selective layer properties were individually optimized. Specifically, nylon 6,6 nanofibers fabricated via electrospinning were used for the first time to form the support structure due to its intrinsic hydrophilicity and superior strength compared to other nanofiber materials. The resulting membrane exhibited half of the structural parameter of a regularly used commercial FO membrane. Furthermore, the selective layer permselectivity could be adjusted using a co-solvent during the interfacial polymerization processes. Adding acetone to the organic phase (hexane) was found to increase permeance and decrease selectivity and hence affect the osmotic flux performance of our membranes. Our best membrane outperformed the standard commercial FO membrane by exhibiting a 1.5 to 2 fold enhanced water flux and an equal or lower specific salt flux.