Tunable
gating graphene oxide (GO) membranes with high water permeance
and precise molecular separation remain highly desired in smart nanofiltration
devices. Herein, bioinspired by the filtration function of the renal
glomerulus, we report a smart and high-performance graphene oxide
membrane constructed via introducing positively charged
polyethylenimine-grafted GO (GO-PEI) to negatively charged GO nanosheets.
It was found that the additional GO-PEI component changed the surface
charge, improved the hydrophilicity, and enlarged the nanochannels.
The glomerulus-inspired graphene oxide membrane (G-GOM) shows a water
permeance up to 88.57 L m–2 h–1 bar–1, corresponding to a 4 times enhancement
compared with that of a conventional GO membrane due to the enlarged
confined nanochannels. Meanwhile, owing to the electrostatic interaction,
it can selectively remove positively charged methylene blue at pH
12 and negatively charged methyl orange at pH 2, with a removal rate
of over 96%. The high and cyclic water permeance and highly selective
organic removal performance can be attributed to the synergic effect
of controlled nanochannel size and tunable electrostatic interaction
in responding to the environmental pH. This strategy provides insight
into designing pH-responsive gating membranes with tunable selectivity,
representing a great advancement in smart nanofiltration with a wide
range of applications.
Carbon nanomaterials have proven
their wide applicability in molecular
separation and water purification techniques. Here, an unzipped carbon
nanotubes (CNT) embedded graphene oxide (GO) membrane (uCNTm) is reported.
The multiwalled CNTs were longitudinally cut into multilayer graphene
oxide nanoribbons by a modified Hummer method. To investigate the
varying effects of different bandwidths of unzipped CNTs on their
properties, four uCNTms were prepared by a vacuum-assisted filtration
process. Unzipped-CNTs with different bandwidths were made by unzipping
multiwalled CNTs with outer diameters of 0–10, 10–20,
20–30, and 30–50 nm and named uCNTm-1, uCNTm-2, uCNTm-3,
and uCNTm-4, respectively. The uCNTms exhibited good stability in
different pH solutions, and the water permeability of the composite
membranes showed an increasing trend with the increase of the inserted
uCNTm’s bandwidth up to 107 L·m–2·h–1·bar–1, which was more than
10 times greater than that of pure GO membranes. The composite membranes
showed decent dye screening performance with the rejection rate of
methylene blue and rhodamine B both greater than 99%.
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