Environmental Engineering Reference
In-Depth Information
~110 0 GPa).
11,12
Hence, graphene has found application possibilities in diverse ields, includ-
ing electronics, catalysis, fuel cells, photovoltaics, biology (including targeted delivery),
etc. The dificulty for bulk synthesis of graphene was a limiting factor of it being utilized
in several ields. Introduction of synthetic approaches such as chemical vapor deposition
(CVD),
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chemical methods, and self-assembly processes have solved this problem, open-
ing the door for graphene to venture into new turf.
Clean water is an essential commodity for all life forms. Cleaning up polluted water
and monitoring the level of contamination are two important processes to ensure the well-
being of society. A great deal of research is going on in this area. Nanomaterials, in gen-
eral, with a greater number of reaction sites per unit area and exceptional surface space,
are known to exhibit enhanced eficacy for removing various contaminants from air and
water compared with their bulk counterparts.
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They have proven to be useful in pollutant-
sensing strategies as well.
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Nanocarbons (e.g., CNTs and carbon onions) have also shown
enhanced capacity over bulk carbon. However, until recently, graphene or graphenic mate-
rials found little application in this area. The perfect planar 2-D structures (ensuring high
direct contact) and huge surface area (~2630 m
2
/g )
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of graphene makes it an ideal candi-
date for decontamination applications.
High mobility, quantum capacitance, and ability to conduct electrons with minimal scat-
tering makes graphene an attractive candidate for sensing-related applications as well.
The abundance of functional groups that enable easy functionalization combined with
high surface area makes chemically synthesized graphene, usually referred to as graphene
oxide (GO) and reduced GO (RGO) or chemically converted graphene, an exceptional pros-
pect for environmental applications. Graphene, alone or as a hybrid in combination with
other constituents, can be eficiently used for the degradation or removal of contaminants.
Speciic functionalization of graphene can lead to targeted sensing as well. In this chap-
ter, a few interesting examples of graphene being used as a substrate for contaminant
removal and sensing are discussed. This chapter discusses mainly the recent develop-
ments. However, a few highly important breakthroughs of the past are also noted.
34.1 Graphene for Environmental Remediation
Diverse forms of carbon such as charcoal, activated carbon (AC), and graphite have been
used for water puriication since ancient times. Carbon-based nanomaterials such as CNTs
(alone or in combination with other materials as composites) have also found tremendous
utility in this ield. Very recently, graphenic materials (graphene, its chemical analogs
GO and RGO) have also shown exceptional promise in this area. Pristine graphene or as
composite with various other materials have been used for this purpose. Various strate-
gies have been employed for this: (i) adsorption, (ii) capacitive deionization, (iii) photo-
catalytic degradation, (iv) other catalytic degradation, (v) removal using graphene-based
membranes, etc. Another important aspect about graphene, its antibacterial activity, which
helps graphene ight against microbial contamination, is also mentioned in the section.
34.1.1 Graphene as an Adsorbent
Adsorption, being the most effective strategy to remove contaminants from dilute solu-
tions, is widely applied for water puriication. Bulk carbon (including AC, graphite, etc.)
