Fabrication and characterization of forward osmosis hollow fiber membranes with antifouling NF-like selective layer

A new type of forward osmosis (FO) hollow fiber membranes with an antifouling nanofiltration (NF)-like selective layer has been developed in this work. The fabrication involves a step of porous poly(amide-imide) (PAI) ultrafiltration (UF) hollow fiber spinning via phase inversion, followed by simple polyelectrolyte post-treatments using positively charged polyethyleneimine (PEI) for cross-linking and negatively charged polystyrene sulfonate sodium salt (PSS) for deposition. The membranes are subsequently characterized by a series of standard protocols and evaluated in FO process. The PAI FO membranes possess a pure water permeability of 3.7–4.3 L m−2 h−1 bar−1 and Na2SO4 rejections up to 85% at 1 bar. In the FO process, the membranes can achieve water flux of 17 and 12 L m−2 h−1 for active layer facing draw solution (AL-facing-DS) and active layer facing feed water (AL-facing-FW) configurations, respectively, using a 2000 ppm Na2SO4 aqueous solution as the feed and 0.5 M Na2SO4 as the draw solution. When the feed contained 1000 ppm bovine serum albumin (BSA) and 2000 ppm Na2SO4, a steady water flux of 11 L m−2 h−1 can be maintained using 0.5 M Na2SO4 as the draw solution at ambient temperature of 23 °C. The approach of making FO membranes developed in the present study offers the advantages of simple fabrication process, tailorable selective layer and promising membrane performance for protein-contained wastewater treatment by FO process.