Development of loose nanofiltration PVDF hollow fiber membrane for dye/salt separation

The fabrication of loose nanofiltration (LNF) membranes for effective separation of dye/salt wastewater mixtures remains a great challenge. In this study, a new method for preparing a LNF membrane is proposed by combining co-extrusion technology and chemical cross-linking. Poly(styrene maleic anhydride (PSMA), an amphipathic copolymer was first entrapped onto the outer surface of poly(vinylidene fluoride) (PVDF) hollow fiber membranes (HFMs) by spinning using a triple orifice spinneret. Subsequently, the prepared PVDF/PSMA membranes were cross-linked using polyethylenimine (PEI) or poly(allylamine hydrochloride) (PAH). Finally, the chemical structure, morphology, hydrophilicity, zeta potential, and pore size were studied systematically. The small pore size and strong positive charge of the prepared membranes contributed to the high rejection of various dyes (>99 %) and low salt rejection (<8.5 %). The prepared membranes also exhibited excellent stability during long-term filtration. Antifouling experiments demonstrated that the prepared LNF membrane had good fouling reduction properties against bovine serum albumin (BSA) and lysozyme (LYZ). This study provides new perspectives for the design of useful LNF HFMs for the treatment of dye/salt wastewater mixtures.