Poly(phthalazinone ether sulfone ketone) (PPESK) hollow fiber asymmetric nanofiltration membranes: Preparation, morphologies and properties

Using ethylene glycol methyl ether (EGME) or acetic acid (AA) as additives and N-methyl-2-pyrrolidone (NMP) as a solvent, defect-free skinned poly(phthalazinone ether sulfone ketone) (PPESK) hollow fiber asymmetric nanofiltration membranes were prepared by dry/wet phase inversion technique from 23 wt.% solids of PPESK/additive/NMP solutions. The pure water was used as a coagulant media. The effects of non-solvent additive on the membrane morphologies and separation performance of PPESK hollow fiber membranes were studied. The membrane structures of PPESK hollow fiber membranes including the cross-section (CS) of the inner edge and the outer edge and the external surface were characterized by scanning electron microscopy (SEM). It was found that using EGME, AA or the combination of them as additives can improve the permeation flux and solute rejection by changing the membrane morphology from finger-like shape to the sponge-like structure. Based on the experimental results, both the membrane performance and the membrane structures were correlated and the pure water permeation fluxes of PPESK hollow fiber membranes can reach 211 L m−2 h−1 while the molecular weight cut-off is approximately 600 (96.1%), determined by PEG.