Abstract
Smart tuning of the membrane's porous nanostructures offers an effective strategy for creating state-of-the-art, high-performance separation membranes. In aqueous solution, polyethylene glycol (PEG) grafted boron nitride PEGX-g-(f-BN) nanosheets exhibit high permeance and excellent molecular sieving. The molecular selectivity of the PEGX-g-(f-BN) lamellar membrane is controlled by the nanopores, which can be tuned by modulating the interplanar spacing between the nanosheets. Herein, the interplanar spacing of h-BN nanosheets is enhanced in the range of 0.334–0.348 nm through grafting different molecular weight PEG. Moreover, the grafted PEG instigates a synergistic effect on the nanosheets in two ways. Firstly, through PEG intercalation, the interlayer spacing of the (002) plane could be adjusted without significant deterioration to the hexagonal crystallographic structure. Secondly, intercalated PEG in BN nanosheets reflects in terms of improved h-BN wettability through transformation to hydrophilic surface characteristics (small contact angle of 36–39°). The fabricated PEGX-g-(f-BN) lamellar membrane acquires stable and interconnected nanopores and nanochannels with an average pore diameter of 1.36–2.19 nm. Permeance-exclusion trade-off manipulation through methodical approaches of PEGX-g-(f-BN) decoration thickness and interplanar spacing is exploited to build a better understanding of water transport behavior. PEGX-g-(f-BN) lamellar membranes show unprecedented permeance of ∼1253 L m−2 h−1 bar−1 with a steady methyl blue (MB) exclusion of 98.9% even in different pH conditions.
Figure: PEG8K-g-(f-BN) lamellar membrane performance in terms of lamellar membrane thickness (a) Fouling and flux recovery analysis, (b) 5 ppm MB permeance and exclusion over three cycles of operation, (c) PEG (Mn 4000) separation and, (d) Permeation and separation of MB solution through PEG8K-g-(f-BN) nanosheet lamellar membrane under pH = 4, 7 and 10. [Display omitted]
•Polyethylene glycol intercalated boron nitride nanosheets with enhanced water transportation.•Interplanar spacing tuning of BN nanosheets through varying chain length of polyethylene glycol.•Pure water and methylene blue solution permeance and solute exclusion analysis for water transportation mechanism.•Permeance-Exclusion trade-off being manipulated through methodical approach.