m-xylene, respectively. The adsorption capacities of TEX onto CNTs-KOH
increased with contact time and decreased with temperature and are not significantly
affected by humic acid.
Yu et al. (2016) utilized magnetic Fe 3 O 4 @MWCNTs through KOH activation
for adsorption study of TEX. The effects of pH and ionic strength on the adsorption behaviors of TEX were also examined and found to be highly pH, ion
strength, and temperature dependent. The maximum adsorption capacity was
observed at pH 6 for TEX pollutants. Yu and co-worker compared adsorption
properties for TEX pollutants with other reported studies. The Fe 3 O 4 @MWCNTs
-KOH composites exhibited high adsorption capacity for TEX onto APCNTsKOH in a decrease order of ethylbenzene >m-xylene >o-xylene >p-xylene >
toluene (227.05, 138.04, 63.34, 249.44, and 105.59 mg/g). The adsorption
isotherms fitted well with the Langmuir and D-R models and followed the pseudosecond-order model for the adsorption of all TEX pollutants. Abbas et al. (2017)
used wet impregnation technique for synthesizing iron oxide impregnated CNTs
and used for removal of toluene and p-xylene. They studied effect of contact time,
adsorbent amount, and initial concentration. Results demonstrated higher removal
of p-xylene compared with toluene under almost similar experimental conditions.
Adsorption capacity of p-xylene was calculated using Langmuir model fit as
219 mg/g and 458 mg/g for pure and iron oxide impregnated CNTs while it was
127 mg/g and 381 mg/g for toluene adsorption using pure and iron oxide
impregnated CNTs.
Graphene (GN) has a large theoretical specific surface area of 2620 m
2 g
À1 and
large delocalized π -electrons which indicate its potential for the adsorption of
various pollutants in environment (Guo et al. 2014). With the help of oxidation
processes the GN can be oxidized to form graphene oxides (GOs), with a range of
surface O-functionalities such as -OH, –CO, and –COOH, -OC 6 H 5 (Geim 2009;
Allen et al. 2010; Patel et al. 2019; Pei and Cheng 2012; Mauter and Elimelech
2008). With functional group manipulations, these structures can easily disperse
in aqueous solution through bonding with polar structure. In literature, graphene
and its derivatives have been widely employed for adsorption of various
pollutants such as heavy metals, dyes, phenol, pesticide, pharmaceuticals, and
hydrocarbons. Some studies have reported the efficiency of GN and GO for
adsorption of PAHs.
Wang et al. (2014a) studied the adsorption of polycyclic aromatic hydrocarbons
by GN and GO nanosheets and evaluated the role of morphology and the delocalized
π-electron system in the adsorption of organic molecules (PAHs) onto adsorbent
(graphene nanomaterials). 3-PAHs, namely naphthalene, phenanthrene, and pyrene
were chosen as the adsorbates for this study. In results, GN displayed high affinity to
the polycyclic aromatic hydrocarbons (PAHs), whereas after attaching oxygen to
GN, GO adsorption was significantly reduced. The high affinities of the PAHs to GN
are dominated by π À π interactions. The relative adsorption affinity of the
contaminants was naphthalene
A. Singh et al.
increased with contact time and decreased with temperature and are not significantly
affected by humic acid.
Yu et al. (2016) utilized magnetic Fe 3 O 4 @MWCNTs through KOH activation
for adsorption study of TEX. The effects of pH and ionic strength on the adsorption behaviors of TEX were also examined and found to be highly pH, ion
strength, and temperature dependent. The maximum adsorption capacity was
observed at pH 6 for TEX pollutants. Yu and co-worker compared adsorption
properties for TEX pollutants with other reported studies. The Fe 3 O 4 @MWCNTs
-KOH composites exhibited high adsorption capacity for TEX onto APCNTsKOH in a decrease order of ethylbenzene >m-xylene >o-xylene >p-xylene >
toluene (227.05, 138.04, 63.34, 249.44, and 105.59 mg/g). The adsorption
isotherms fitted well with the Langmuir and D-R models and followed the pseudosecond-order model for the adsorption of all TEX pollutants. Abbas et al. (2017)
used wet impregnation technique for synthesizing iron oxide impregnated CNTs
and used for removal of toluene and p-xylene. They studied effect of contact time,
adsorbent amount, and initial concentration. Results demonstrated higher removal
of p-xylene compared with toluene under almost similar experimental conditions.
Adsorption capacity of p-xylene was calculated using Langmuir model fit as
219 mg/g and 458 mg/g for pure and iron oxide impregnated CNTs while it was
127 mg/g and 381 mg/g for toluene adsorption using pure and iron oxide
impregnated CNTs.
Graphene (GN) has a large theoretical specific surface area of 2620 m
2 g
À1 and
large delocalized π -electrons which indicate its potential for the adsorption of
various pollutants in environment (Guo et al. 2014). With the help of oxidation
processes the GN can be oxidized to form graphene oxides (GOs), with a range of
surface O-functionalities such as -OH, –CO, and –COOH, -OC 6 H 5 (Geim 2009;
Allen et al. 2010; Patel et al. 2019; Pei and Cheng 2012; Mauter and Elimelech
2008). With functional group manipulations, these structures can easily disperse
in aqueous solution through bonding with polar structure. In literature, graphene
and its derivatives have been widely employed for adsorption of various
pollutants such as heavy metals, dyes, phenol, pesticide, pharmaceuticals, and
hydrocarbons. Some studies have reported the efficiency of GN and GO for
adsorption of PAHs.
Wang et al. (2014a) studied the adsorption of polycyclic aromatic hydrocarbons
by GN and GO nanosheets and evaluated the role of morphology and the delocalized
π-electron system in the adsorption of organic molecules (PAHs) onto adsorbent
(graphene nanomaterials). 3-PAHs, namely naphthalene, phenanthrene, and pyrene
were chosen as the adsorbates for this study. In results, GN displayed high affinity to
the polycyclic aromatic hydrocarbons (PAHs), whereas after attaching oxygen to
GN, GO adsorption was significantly reduced. The high affinities of the PAHs to GN
are dominated by π À π interactions. The relative adsorption affinity of the
contaminants was naphthalene
A. Singh et al.