used as a novel adsorbent for the preconcentration of carbofuran, metolcarb,
pirimicarb, diethofencarb, and isoprocarb (Wu et al. 2011b). The as-fabricated
nanocomposite showed excellent super paramagnetic properties and adsorption
capacity. A magnetic microsphere Fe 3 O 4 /SiO 2 /graphene composite was fabricated
as a new adsorbent for the preconcentration of di-n-propyl-phthalate, diallyl phthalate, dicyclohexyl phthalate, benzyl butyl phthalate, and diethylhexyl phthalate in
soybean milk and water samples (Wang et al. 2013c). The Fe 3 O 4 /graphene
nanocomposite prepared by solvothermal route effectively removed aniline from
their aqueous solution within 60 mins (Chang et al. 2012). The composites showed a
promising adsorbent for phthalate esters with potential applications. A magnetic
Fe 3 O 4 /graphene composite was used for the extraction of some sulfonamides
(sulfamerazine, sulfapyridine, sulfamonomethoxine sodium, sulfameter,
sulfadoxine, and sulfachloropyridazine) from the water (Luo et al. 2011). The
composite exhibited efficient extraction media for the enhancement of sulfonamide
antibiotics in water resources.
1.7.2 Graphene-Based Photocatalyst Materials for Water
Treatment
Although adsorption can eliminate pollutants from water/wastewater, this method
cannot completely remove pollutants (Chong et al. 2010). Complete mineralization
of pollutants can be achieved through a photocatalytic technique (Chong et al. 2010).
Recently, semiconductor photocatalyst materials have received global interest in
water remediation application (Hoffmann et al. 1995). Nonetheless, the fast recombination of charge carriers results in a low quantum efficiency, which limits its
potential visible light applications. Hence, reducing the recombination rate of charge
carriers is significant to enhance the photoactivity of semiconductor photocatalysts.
The most significant characteristics of graphene sheet for photodegradation of
pollutants are due to its ability to tune the band gap and absorption edge of
semiconductor photocatalyst materials. The ultrahigh electron conductivity of GR
allows the transfer of electrons from the semiconductor to the graphene surface, and
this contributes to the reduced recombination rate, thus improving the photocatalytic
activity of conventional photocatalysts, such as TiO 2 (Liu et al. 2010). Therefore,
composites that combine semiconductor photocatalysts and graphene might offer a
desired efficiency for separating the charge carriers. Due to its strong oxidizing
activity and low-cost, TiO 2 is the most often used semiconductor for the
photodegradation of pollutants. The popularity of TiO 2 is explained by its commercial availability, such as P90 and P25, which serves as reference reagents for the
fabrication of graphene-based TiO 2 photocatalyst composites (Liu et al. 2010).
Coupling graphene sheets with TiO 2 improved the photoactivity of the composites.
Apart from TiO 2 , several metal oxides, such as WO 3 (An et al. 2012), ZnO (Min
et al. 2012), CuO (Yusoff et al. 2013), Cu 2 O (Gao et al. 2012a), SnO 2 (Seema et al.
16
F. Opoku et al.
pirimicarb, diethofencarb, and isoprocarb (Wu et al. 2011b). The as-fabricated
nanocomposite showed excellent super paramagnetic properties and adsorption
capacity. A magnetic microsphere Fe 3 O 4 /SiO 2 /graphene composite was fabricated
as a new adsorbent for the preconcentration of di-n-propyl-phthalate, diallyl phthalate, dicyclohexyl phthalate, benzyl butyl phthalate, and diethylhexyl phthalate in
soybean milk and water samples (Wang et al. 2013c). The Fe 3 O 4 /graphene
nanocomposite prepared by solvothermal route effectively removed aniline from
their aqueous solution within 60 mins (Chang et al. 2012). The composites showed a
promising adsorbent for phthalate esters with potential applications. A magnetic
Fe 3 O 4 /graphene composite was used for the extraction of some sulfonamides
(sulfamerazine, sulfapyridine, sulfamonomethoxine sodium, sulfameter,
sulfadoxine, and sulfachloropyridazine) from the water (Luo et al. 2011). The
composite exhibited efficient extraction media for the enhancement of sulfonamide
antibiotics in water resources.
1.7.2 Graphene-Based Photocatalyst Materials for Water
Treatment
Although adsorption can eliminate pollutants from water/wastewater, this method
cannot completely remove pollutants (Chong et al. 2010). Complete mineralization
of pollutants can be achieved through a photocatalytic technique (Chong et al. 2010).
Recently, semiconductor photocatalyst materials have received global interest in
water remediation application (Hoffmann et al. 1995). Nonetheless, the fast recombination of charge carriers results in a low quantum efficiency, which limits its
potential visible light applications. Hence, reducing the recombination rate of charge
carriers is significant to enhance the photoactivity of semiconductor photocatalysts.
The most significant characteristics of graphene sheet for photodegradation of
pollutants are due to its ability to tune the band gap and absorption edge of
semiconductor photocatalyst materials. The ultrahigh electron conductivity of GR
allows the transfer of electrons from the semiconductor to the graphene surface, and
this contributes to the reduced recombination rate, thus improving the photocatalytic
activity of conventional photocatalysts, such as TiO 2 (Liu et al. 2010). Therefore,
composites that combine semiconductor photocatalysts and graphene might offer a
desired efficiency for separating the charge carriers. Due to its strong oxidizing
activity and low-cost, TiO 2 is the most often used semiconductor for the
photodegradation of pollutants. The popularity of TiO 2 is explained by its commercial availability, such as P90 and P25, which serves as reference reagents for the
fabrication of graphene-based TiO 2 photocatalyst composites (Liu et al. 2010).
Coupling graphene sheets with TiO 2 improved the photoactivity of the composites.
Apart from TiO 2 , several metal oxides, such as WO 3 (An et al. 2012), ZnO (Min
et al. 2012), CuO (Yusoff et al. 2013), Cu 2 O (Gao et al. 2012a), SnO 2 (Seema et al.
16
F. Opoku et al.