Dielectric constant of electrolyte solutions confined in a charged nanofiltration membrane

Abstract

A facile coordination-driven assembly strategy is proposed to construct a multifunctional PSS-metal ions complex interlayer on the substrate for the fabrication of the high performance thin-film composite (TFC) NF membrane with crumpled morphology. The PSS-metal ions interlayer not only acts as nanoscaffold role to provide a more uniform interfacial polymerization (IP) platform that is favorable for forming a thinner and free-defect PA layer with less PA intruded into the pores of support, but also works as macromolecule addition to induce the diffusion-driven instability of IP process that causes the creation of the crumpled PA layer with increased surface area, of which dual roles in regulating the IP process are confirmed by the comprehensive characterization of the top and back surface morphologies and structure of the selective layer. As such, the obtained TFC membrane exhibits a four folds of permeance (up to 22.15 ± 1.14 L m−2 h−1 bar−1) as compared with traditional TFC-0 membrane, while maintaining a competitive rejection for Na2SO4 (about 99.3%). Moreover, owing to the increased surface negative charges and decreased effective pore size, the novel NF membrane shows a simultaneous high rejection of trace organic compounds (TrOCs) and low retention of divalent cation (Ca2+/Mg2+) in a real tap water, suggesting that it has great potential in drinking water treatment. This study provides a new direction to prepare the high-performance TFC membrane for water purification.