addressing the global environmental issues due their high mechanical strength,
excellent electron mobility, large surface area, and high thermal conductivity.
Semiconductor photocatalysis has received much interest as a promising technology
for water treatment owing to its cost-effective, easy operation, high-efficiency, and
convenience. Therefore, the design and fabrication of graphene support with semiconductor photocatalyst are promising as multifunctional catalysts. This book chapter evaluates the recent design of graphene-based materials as adsorbent and
photocatalytic materials in environmental remediation. The theoretical outcomes in
water treatment using graphene/semiconductor composites are also summarized. A
brief outlook on the challenges and new strategies is provided for developing
effective water/wastewater treatment techniques using graphene-based materials.
Keywords Nanotechnology · Water treatments · Photocatalyst · Semiconductor ·
Composites
1.1 Introduction
The release of municipal, agricultural, industrial, and domestic waste effluents into
water resources has certainly given rise to a lot of toxic contaminants (Marahel et al.
2015). Heavy metal ions and dyes have attracted serious concern owing to their
non-biodegradable, high toxicity and tend to accumulate in the tissues of living
organisms (Fu and Wang 2011a). The highly toxic and non-biodegradable of most
dye molecules is due to the aromatic ring in their structure (Hou et al. 2012).
Furthermore, dyes add adverse color to water resources, which prevent the penetration of sunlight to retard photosynthetic reactions, thereby affecting aquatic life
(Marahel et al. 2015). Therefore, the recycling and reuse of wastewater effluents
are necessary to enhance the limited fresh water supply (Qu and Fan 2010). Hence, it
is essential to minimize dyes and heavy metal ions to acceptable limits before being
discharged to water bodies. During the past few decades, several techniques have
been realized to design feasible wastewater/water treatment technologies (Gupta
et al. 2012). For example, biological treatments are designed to successfully remove
various forms of pollutants from water/wastewater resources; nonetheless, this
technique also usually produce secondary pollution (Ganzenko et al. 2014), as
well as health-threatening bacteria, and soluble refractory organic compounds,
which are difficult to remove (Ray et al. 2013). Therefore, developing green,
nondestructive, and sustainable technologies for water/wastewater treatment is of
much importance.
As a green, nondestructive, and promising technology, heterogeneous semiconductor photocatalysis has recently received broad interest for wastewater/water
treatment owing to its effectiveness to remove harmful bacteria and pollutants
(Yang et al. 2010). Mostly, the semiconductors can be photoactivated by a photon,
which has an energy equal to or greater than its band gap (E g ) (Fageria et al. 2014).
As a renewable and safe energy source, the solar energy is the best energy supply
2
F. Opoku et al.
excellent electron mobility, large surface area, and high thermal conductivity.
Semiconductor photocatalysis has received much interest as a promising technology
for water treatment owing to its cost-effective, easy operation, high-efficiency, and
convenience. Therefore, the design and fabrication of graphene support with semiconductor photocatalyst are promising as multifunctional catalysts. This book chapter evaluates the recent design of graphene-based materials as adsorbent and
photocatalytic materials in environmental remediation. The theoretical outcomes in
water treatment using graphene/semiconductor composites are also summarized. A
brief outlook on the challenges and new strategies is provided for developing
effective water/wastewater treatment techniques using graphene-based materials.
Keywords Nanotechnology · Water treatments · Photocatalyst · Semiconductor ·
Composites
1.1 Introduction
The release of municipal, agricultural, industrial, and domestic waste effluents into
water resources has certainly given rise to a lot of toxic contaminants (Marahel et al.
2015). Heavy metal ions and dyes have attracted serious concern owing to their
non-biodegradable, high toxicity and tend to accumulate in the tissues of living
organisms (Fu and Wang 2011a). The highly toxic and non-biodegradable of most
dye molecules is due to the aromatic ring in their structure (Hou et al. 2012).
Furthermore, dyes add adverse color to water resources, which prevent the penetration of sunlight to retard photosynthetic reactions, thereby affecting aquatic life
(Marahel et al. 2015). Therefore, the recycling and reuse of wastewater effluents
are necessary to enhance the limited fresh water supply (Qu and Fan 2010). Hence, it
is essential to minimize dyes and heavy metal ions to acceptable limits before being
discharged to water bodies. During the past few decades, several techniques have
been realized to design feasible wastewater/water treatment technologies (Gupta
et al. 2012). For example, biological treatments are designed to successfully remove
various forms of pollutants from water/wastewater resources; nonetheless, this
technique also usually produce secondary pollution (Ganzenko et al. 2014), as
well as health-threatening bacteria, and soluble refractory organic compounds,
which are difficult to remove (Ray et al. 2013). Therefore, developing green,
nondestructive, and sustainable technologies for water/wastewater treatment is of
much importance.
As a green, nondestructive, and promising technology, heterogeneous semiconductor photocatalysis has recently received broad interest for wastewater/water
treatment owing to its effectiveness to remove harmful bacteria and pollutants
(Yang et al. 2010). Mostly, the semiconductors can be photoactivated by a photon,
which has an energy equal to or greater than its band gap (E g ) (Fageria et al. 2014).
As a renewable and safe energy source, the solar energy is the best energy supply
2
F. Opoku et al.