High-flux robust PSf-b-PEG nanofiltration membrane for the precise separation of dyes and salts

• High-flux PSf- b -PEG membrane was fabricated for precise separation of dye/salt. • The PSf- b -PEG membrane has superior mechanical strength of 22.4 ± 0.9 MPa. • Pore size of the membrane was 3.8 nm, and MWCO towards dyes was about 655 Da. • The membrane exhibited high rejection for CR dye and nearly 100% Na 2 SO 4 passage. • The water permeance of the membrane was 49.3 ± 0.9 L m − 2 h −1 bar −1 . We report a novel high-flux nanofiltration (NF) membrane for the precise separation of dyes and salts, which was fabricated using polysulfone- block -polyethylene glycol (PSf- b -PEG) block copolymer through the non-solvent induced phase separation (NIPS) method. The PSf- b -PEG membrane exhibited a very dense sponge-like porous structure with rich interconnected pores, contributing to its superior mechanical strength of 22.4 ± 0.9 MPa. The pore size of PSf- b -PEG membrane was mostly distributed around 1.3 nm in diameter with the mean effective pore size of 3.8 nm in diameter, while the membrane molecular weight cut off (MWCO) towards dyes was about 655 Da. The PSf- b -PEG membrane exhibited a very high water permeance of 49.3 ± 0.9 L m −2 h −1 bar −1 and a precise separation of salts and dyes with high above 98% Congo Red dye rejection and nearly 100% Na 2 SO 4 passage, succeeding the separation performances of current NF membranes used for the separation of dyes and salts. Long-term NF tests prove the highly stable and outstanding separation performances of PSf- b -PEG membrane with the top dense skin layer as the effective selective layer. Our work suggests that the PSf- b -PEG membrane has a great potential to be further optimized and used for practical applications.