Environmental Engineering Reference
In-Depth Information
8.7
ConClusion
CNTs offer tremendous opportunity and possibilities for resolving water quality-related problems. Their modifiable surface
properties through covalent and noncovalent functionalization enable the attachment of suitable functional moieties. Thus, the
tunable surface properties of CNTs meet application requirements. Given their high aspect ratio and large surface area, CNT
particles have high sorption capacity toward heavy metals and microorganisms and exhibit superior reusability by maintaining
a stable adsorption performance for over 10 cycles of sorption and desorption. Their contact with microorganisms also reveal
their antimicrobial property, which allows them to inhibit cell activities that eventually lead to cell inactivation. CNTs are
viewed as novel membrane materials that induce immense improvement in membrane-separation processes. CNT-mmms
formed by embedding them into a polymer matrix increase the mechanical properties of the membranes and enhance their
chemical resistance against chlorine. In the fabrication of porous-structured CNT-mmms by the phase-inversion method, the
presence of CNTs facilitates alterations in the membrane structure, which increases membrane hydrophilicity. Consequently,
high water flux and solute rejection are enabled, and the antifouling properties of the membrane are improved. CNTs can also
bundle up as a planar film known as buckypapers. Buckypapers are favorable for mD because of their exceptionally high
thermal stability and efficient vapor transport. Apart from these observations, the highly porous structures possessed by bucky-
papers also make them applicable in the filtration and removal of nanoparticles. Vertically aligned CNT membranes are another
form of CNT-based membranes, where CNTs are uniformly arranged vertically. Although their practical application in water
treatment is scarcely reported, simulation studies have shown that the vertically aligned CNT structure can fully utilize the
advantages of the inner cavities of CNTs as flow channels. The termini of CNTs can serve as gatekeepers to control mass
transport selectively. The environmental impacts of CNTs based on lifecycle assessment reveal the potential release of haz-
ardous materials to the environment during CNT manufacture. However, their highly effective applications potentially reduce
the environmental burden and outweigh their negative impact.
aCknoWledGment
The authors acknowledge the fellowship support of the myPhD program of the ministry of Higher Education malaysia,
universiti Sains malaysia (uSm) Research university Grant, uSm membrane Cluster Grant, uSm fellowship, and the
Fundamental of Research Grant Scheme.
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