High-performance nanofiltration membrane with structurally controlled PES substrate containing electrically aligned CNTs

Abstract

A structurally controlled polyethersulfone (PES) membrane, as the substrate of the thin film composite nanofiltration (NF) membranes, was designed and fabricated with aligned carbon nanotubes (ACNTs) by a direct current electric field. The morphology and properties of the NF membranes were simultaneously affected by the PES substrate with especial macrovoids and ACNTs, increasing the permeability from 6.4 to 29.7 L/m2 h bar. It was confirmed by FT-IR and XPS that the poly(piperazine amide) selective layer of the modified NF membrane has an increased content of –COOH for enhanced hydrophilicity. The zeta potential proves that the surface of the NF membrane modified by electric field has weaker negative charge than that of unmodified membrane in the range of pH = 5–9. Under the combined action of the Donnan effect and size exclusion, the rejection of MgCl2 increased while maintaining the dianion rejection above 95%. Particularly, the NF membrane modified with ACNTs exhibited better chlorine resistance and antifouling ability, thus improving the stability and perdurability of membranes. Our work utilizes the characteristics of ACNTs to explore its potential in NF membranes.