Polyamide membrane with nanoscale stripes and internal voids for high-performance nanofiltration

Stripe patterned nanofiltration (NF) membranes were established via sulfonated polyether sulfone nanoparticles (SPES NPs) regulated interfacial polymerization. The nanoparticle was prepared by nonsolvent-induced phase separation to serve as a regulator, confining piperazine (PIP) diffusion towards organic phase through chemical affinity and steric effect. Consequently, intensive stripes in nanoscale have emerged and were uniformly distributed throughout the membrane. The internal characteristics of the structure were observed and revealed distinguishable ordered voids at the bottom of the polyamide (PA) layer. The generation and evolution, from the conventional nodular structures to stripe patterns, were investigated by optimizing the thickness of pristine NF membranes and incorporating different concentrations of SPES NPs. The resultant SPES-1.0@NFM-II with a distinctive morphology of interconnected labyrinthine networks on top and bottom surfaces of PA active layer, exhibited significant enhancement in water permeance (23.04 L m −2  h −1 bar −1 , versus 12.15 L m −2  h −1 bar −1 of conventional NFM-II) while maintaining excellent divalent salt rejection (99.42% for Na 2 SO 4 ).