Fabrication and characterization of polyurethane/chitosan electrospun nanofiber support membranes for high-performance FO applications

Electrospun nanofiber membranes are promising support for forward osmosis (FO) composite membranes due to their high porosity and low tortuosity. However, achieving a defect-free selective layer is challenging due to the large interconnected pores of nanofiber support. In this study, the potential of polyurethane (PU)/chitosan (CS) blend nanofibrous membrane as substrate for high-performance FO membrane was investigated. PUCS blend solutions were electrospun at optimized compositions to fabricate smooth and bead free nanofibrous membranes. The resulting PUCS nanofibrous membranes exhibited superior mechanical strength compared to pristine PU due to strong interaction between PU and CS at molecular level and their spider-net-like morphology. Thermal pressing enhanced the compactness of the membrane, significantly reducing the surface roughness and thickness of the support layer. Subsequently, a polydopamine (PDA)/Fe3 +-tannic acid (TA) interlayer was introduced to facilitate the deposition of a defect-free polyamide (PA) selective layer through the interfacial polymerization (IP) process, thereby developing a thin film composite (TFC) FO membrane. The modified PUCS-TFC membrane had water flux (Jw) rates of 35.16 LMH and 44.61 LMH with a 1 M NaCl draw solution (DS) and DI water as feed solution (FS), respectively. At the same time, it had a low reverse salt flux (Js) of 3.364 gMH and 1.605 gMH under FO and PRO modes, respectively. The Js/Jw ratio of 0.095 g/L for 1 M NaCl draw solution indicated efficient performance. The FO membrane also demonstrated an anti-fouling property when tested with humic acid. Therefore, the PUCS-TFC membrane demonstrates great potential for applications in desalination.