posted on 2021-08-05, 16:16authored bySally El Meragawi, Abozar Akbari, Tanesh Gamot, Akshat Tanksale, Mainak Majumder
Oxygen
functionalities on graphene oxide (GO) nanosheets have a
significant role in the performance of GO-based laminar membranes.
The influence of these groups on nanochannel spacing, electrostatic
repulsion, and transport resistance in aqueous and polar environments
is well recognized. In this work, the antioxidative properties of
olives, Olea europaea, were exploited
to gradually reduce GO and the effects of progressive deoxygenation
on the properties GO membranes were systematically monitored. The
optimization of the reaction process in this manner enabled the fabrication
of an ultrafast membrane with enhanced molecular sieving characteristics.
Ultrathin (∼30 nm thick) membranes prepared from liquid crystalline
polyphenol–GO dispersions with a water permeance of 60.4 ±
2.8 L·m–2·h–1·bar–1 showed dramatic improvement over GO membranes (water
permeance of 10 ± 3.4 L·m–2·h–1·bar–1). This is combined with
enhanced molecular sieving characteristics of >90% for probes such
as methyl orange with hydrated radii greater than 5.0 Å and stability
in crossflow filtration tests wherein Rose Bengal (974 Da) is retained
at >90% for 100 h compared to GO, which falls below 50% retention
in the same amount of time. This improvement is attributed to the
confluence of the loss of oxygen functional groups and cross-linking
attachment of polyphenols to the GO nanosheets. The results will facilitate
new understanding in the design of novel bio-inspired composite membranes.