Abstract
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.
Highlights
Freshwater shortage and the clean energy crisis are becoming the most important global challenges with increasing population growth, accelerating urbanization, and worsening climate change[1,2]
The mean surface pore size of the block copolymer membrane casted on the PET fabric obviously increased from 20 ± 1 to 26 ± 3 nm upon the post-annealing treatment, as shown in Fig. 1 and Table 1; these values were significantly larger than the corresponding values of 12 and 16 nm for the block copolymer membrane casted on the glass before and after the annealing treatment[19]
Our results show that the pristine block copolymer membrane support provided a favorable surface to form a highly crosslinked polyamide with a very low reverse salt flux
Summary
Freshwater shortage and the clean energy crisis are becoming the most important global challenges with increasing population growth, accelerating urbanization, and worsening climate change[1,2]. Advanced technologies are urgently needed to economically produce eco-friendly freshwater and clean energy. High-performance semipermeable membranes play a key role in the FO process, and thin-filmcomposite (TFC) polyamide membranes are the state-ofthe-art choice for current FO membranes having great. TFC polyamide membranes possess a highly crosslinked polyamide active layer formed through interfacial polymerization on top of a polymeric ultrafiltration (UF) membrane support[5]. Different from other reverse osmosis and nanofiltration membranes, the polyamide active layer and the microporous support determine the water permeability of FO membranes due to the internal concentration polarization (ICP) effect of the support[6,7]. The water flux and salt rejection of TFC FO membranes have great potential to be further improved through optimization of the structure and properties of the porous support[8]
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