Breaking the permeability-selectivity trade-off in thin-film composite polyamide membranes with a PEG-b-PSF-b-PEG block copolymer ultrafiltration membrane support through post-annealing treatment

In this work, amphiphilic polyethylene glycol-block-polysulfone-block-polyethylene glycol (PEG-b-PSF-b-PEG) was used as a membrane support to fabricate a high-performance thin-film composite (TFC) forward osmosis (FO) membrane. A facile post-annealing approach was developed to simultaneously improve the water permeability and antifouling property of the TFC membrane having the PEG-b-PSF-b-PEG support without sacrificing its selectivity. The experimental results illustrate that a highly crosslinked polyamide with low reverse salt flux could be formed on the PEG-b-PSF-b-PEG support, and the post-annealing treatment could tailor the membrane structure and properties of the PEG-b-PSF-b-PEG support to decrease its structure parameter without affecting the polyamide. The annealed TFC membrane exhibited excellent permeability-selectivity, with a high A/B ratio of 19.6 bar(-1) (water permeability coefficient A of 1.76 LMH.bar(-1) and NaCl permeability coefficient B of 0.09 LMH). The static and dynamic antifouling performances of the annealed TFC membrane were also demonstrated, finding that little bovine serum albumin (BSA) was adsorbed on the PEG-b-PSF-b-PEG support surface, and a reduced water flux decline and a high water recovery were achieved compared with those of the control sample. Our work demonstrates that the amphiphilic PEG-b-PSF-b-PEG membrane can work as an ideal TFC support to break the permeability-selectivity trade-off of the TFC FO membrane and to improve its antifouling properties through post-annealing treatment