Dual-Layer Hollow Fibers with Enhanced Flux As Novel Forward Osmosis Membranes for Water Production

We have demonstrated in this work the prospect of dual-layer polybenzimidazole-polyethersulfone (PBI-PES) nanofiltration (NF) hollow fiber membranes in the forward osmosis (FO) process for water production: The state-of-the-art for dual-layer membrane fabrication via coextrusion technology could produce the resultant membrane consisting of an ultrathin selective skin, fully porous water channels underneath, and a microporous sponge-like support structure. Together with its sharp pore size distribution and self-charged PBI selective membrane surface, the dual-layer hollow fiber forward osmosis membrane can achieve a water flux as high as 33.8 L·m−2·hr−1 and a salt flux less than 1.0 g·m−2·hr−1 at room temperature of 23 °C using 5 M MgCl2 as the draw solution. A comprehensive literature review of previous efforts on identifying suitable membranes and appropriate draw solutions in the FO process for water production and seawater desalination have also been conducted. It shows that the water fluxes of the dual-layer hollow fiber FO membrane developed in this work utilizing MgCl2 as the draw solutions generally surpasses those FO processes utilizing RO membranes and is comparable to most FO processes using commercial FO membrane and employing other salts or sugar instead of MgCl2 as the draw solutions.