Performance improvement for thin-film composite nanofiltration membranes prepared on PSf/PSf-g-PEG blended substrates

For the first time, the amphiphilic polysulfone-graft-polyethylene glycol (PSf-g-PEG) was incorporated with PSf substrates for preparing composite nanofiltration (NF) membranes. The PSf/PSf-g-PEG blended substrates and NF membranes formed thereon by interfacial polymerization of piperazine (PIP) with 1,3,5-benzenetricarbonyl trichloride (TMC) were characterized in terms of chemical compositions, morphologies, porosity, roughness, and hydrophilicity. NF performance was assessed by permeability and rejections of Na2SO4, MgSO4, MgCl2 and NaCl solutions. The NF performance was shown to be enhanced in both respects of pure water permeability and salt rejections by increasing the content of PSf-g-PEG in substrates. When the content of PSf-g-PEG was 10 wt%, the fabricated NF membrane (NF-4) achieved the highest pure water permeability and the optimum Na2SO4 rejection that were increased by 139% and 21%, respectively, compared to the control NF membrane formed from the pure PSf substrate. The great improvement in NF performance was contributed by the modified surface properties (e.g., porosity, hydrophilicity) of PSf/PSf-g-PEG blended substrates. Therefore, this work suggests that blending the amphiphilic copolymer PSf-g-PEG with PSf substrates could be an effective approach to improving NF performance.