Positively-charged nanofiltration membrane formed by quaternization and cross-linking of blend PVC/P(DMA-co-MMA) precursors

To explore low-pressure-driven nanofiltration (LPDNF) membranes with high permeate flux , a novel preparation route was proposed and investigated. First, an amphiphilic copolymer of poly (methyl methacrylate- co -dimethylaminoethyl methacrylate) (P(MMA- co -DMA)) was synthesized via free-radical copolymerization , and then blended with polyvinyl chloride (PVC) to fabricate precursor membranes via non-solvent induced phase separation (NIPS) process. Utilizing the quaternization and cross-linking reaction between p -xylylene dichloride (XDC) and tertiary amine units in PVC/PMMA- co -DMA precursor membranes, positively charged PVC/PMMA- co -DMA LPDNF membranes were obtained. Element alanalysis, X-ray photoelectron spectroscopy and scanning electron microscopy were employed to characterize the composition and morphology of the membranes. Effects of PMMA- co -DMA content and XDC concentration on the LPDNF membranes’ performance were studied and discussed. With the optimized condition, the NF membrane showed the highest salt rejection ( R ) and water flux ( J ), e.g., R MgCl 2 =89.1%, J MgCl 2 =22.1   L/(m 2   h) and R NaCl =45.1%, J NaCl =27.6   L/(m 2   h) at a pressure of 0.3   MPa. Besides, the rejections of the LPDNF membranes for inorganic salts increased in an order of Na 2 SO 4