High-flux and chlorine-resistant nanofiltration membrane fabricated via phase inversion using polysulfone-b-polyglycerol hyperbranched block copolymer

Abstract

The nanofiltration (NF) membranes having excellent chlorine resistance and sufficient perm-selectivity are highly desired in drinking water treatment and other applications. Herein, a novel block copolymer NF membrane with superior chlorine resistance, especially high water permeance was prepared via phase inversion, using a tailor-made polysulfone-block-hyperbranched polyglycerol (PSf-b-hPG) material. The fabricated PSf-b-hPG NF membrane shows an extremely thin separation layer with a thickness of around 80 nm and a high overall porosity of 65 %, thanks to the structural advantage of hyperbranched hydrophilic hPG segments and the unique feature of the PSf-b-hPG casting solution of possessing a very low viscosity at a high solid content. The membrane exhibits an effective pore diameter of 1.6 nm, and the molecular weight cut-off (MWCO) was around 4 kDa. The membrane displayed extremely high pure water permeance of 34 LMH/bar as well as a satisfactory Na2SO4 rejection of 74 %. Moreover, the membrane exhibits superior chlorine resistance with no change in separation performance when challenged with 36,000 ppm∙h chlorination intensity and also maintains a stable Na2SO4 rejection and water permeance during the 14 h NF test. Our results suggest the NF membrane prepared by PSf-b-hPG has superior chlorine resistance and high water permeance, and is capable of efficiently removing sulfate from drinking water or others.