The characteristics
of aerogel materials such as the low density
and large surface area enable them to adsorb large amounts of substances,
so they show great potential for application in industrial wastewater
treatment. Herein, using a combination of completely environmentally
friendly materials such as cellulose nanofibers (CNFs) extracted from
the petioles of the nipa palm tree and graphene oxide (GO) fabricated
by simple solvent evaporation, a composite aerogel was prepared by
a freeze-drying method. The obtained aerogel possessed a light density
of 0.0264 g/cm
3
and a porosity of more than 98.2%. It was
able to withstand a weight as much as 2500 times with the maximum
force (1479.5 N) to break up 0.2 g of an aerogel by compression strength
testing and was stable in the aquatic environment, enabling it to
be reused five times with an adsorption capacity over 90%. The CNF/GO
aerogel can recover higher than 85% after 30 consecutive compression
recovery cycles, which is convenient for the reusability of this material
in wastewater treatments. The obtained aerogel also showed a good
interaction between the component phases, a high thermal stability,
a 3D network structure combined with thin walls and pores with a large
specific surface area. In addition, the aerogel also exhibited a fast
adsorption rate for methylene blue (MB) adsorption, a type of waste
from the textile industry that pollutes water sources, and it can
adsorb more than 99% MB in water in less than 20 min. The excellent
adsorption of MB onto the CNF/GO aerogel was driven by electrostatic
interactions, which agreed with the pseudo-second-order kinetic model
with a correlation coefficient
R
2
= 0.9978.
The initial results show that the CNF/GO aerogel is a highly durable
“green” light material that might be applied in the
treatment of domestic organic waste water and is completely recoverable
and reusable.
Polyvinyl alcohol (PVA) is well-known in the packaging industry, especially in the food and medical fields with the ability to be completely biodegradable and easily soluble in cold water therefore products made from it are the environmentally friendly materials. However, the disadvantages of this polymer as quick dissolubility in water, poor moisture retention, weak mechanical properties reduce its applications. In this study, PVA, reinforced by “green” components at the nanometer-level such as nanocellulose fibers (CNF), graphene oxide (GO) nanosheets showed improvements in properties. Mechanical properties of all of nanocomposite films showed improvements in stress at break and modulus. Especially, reinforced GO and CNF films increased almost doubled and improved more 40% in modulus than the pure PVA film and films reinforced by only GO or CNF. When immersed in water (neutral pH) at room temperature, graphene oxide-reinforced films not only had effective improvements in swelling time but also supported to decrease water retension of film added CNF. The combined reinforcement also indicated a benefit in reducing the rate of water vapor loss of the film as well as the efficiency in declining the moisture absorption of the nanocomposite films. The PVA films reinforced by nanocellulose fibers and graphene oxide sheets overcomed some of the PVA's shortcomings. This helped expanding its applications in the field of environmentally friendly nanocomposite films.
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