increase 81.98% and 14.7%, respectively. Purification also introduced oxygencontaining groups on the surface of the SWCNTs. Results indicated that adsorption
behavior of the SWCNTs for o-xylene greatly changed after the purification.
Surface modification of carbon nanotubes has been widely acknowledged as
an effective method to enhance the performance for particular purposes, which
can be easily achieved with different methods (Norzilah et al. 2011; Lu et al.
2008). The maximum adsorption of pollutant on CNTs depends upon pore
structure and oxygen functional groups (-OH, –CO, and –COOH), which depend
upon fabrication and purification methods. Lu et al. (2008) fabricated carbon
nanotubes by the catalytic chemical vapor deposition method and oxidized by
HCl, H 2 SO 4 , HNO 3, and NaOCl solutions for enhancing benzene, toluene, ethylbenzene, and p-xylene (BTEX) adsorption in an aqueous solution. With this
method surface nature of CNTs was changed which makes CNTs that adsorb
more BTEX. The CNT (NaOCl) have the greatest enhancement in adsorption
capacity for BTEX, followed by the CNT(HNO 3 ), CNT(H 2 SO 4 ), CNT, and then
the CNT(HCl). This suggested that the NaOCl oxidized CNTs are efficient BTEX
adsorbents and that they possess good potential applications for BTEX removal in
wastewater treatment. The adsorption mechanism of BTEX on CNTs was also
suggested which is mainly due to the π–π electron donor–acceptor interactions
between the aromatic ring of BTEX and the surface carboxylic groups of CNTs
(Fig. 9.8).
Ji et al. (2010) found that KOH dry etching is a useful activation method for
SWCNTs and MWCNTs to improve the adsorption affinity and adsorption reversibility of organic contaminants on carbon nanotubes. For this study, they chose
monoaromatic compounds (phenol and nitrobenzene) and pharmaceutical antibiotics
(sulfamethoxazole, tetracyclineandtylosin) in aqueous solutions. Yu et al. (2012)
also activated multi-walled carbon nanotubes by KOH (CNTs-KOH) and employed
as adsorbents to study adsorption characteristics of toluene, ethylbenzene, and mxylene (TEX) from aqueous solutions. The maximum adsorption capacities on
CNTs-KOH are 87.12, 322.05, and 247.83 mg/g for toluene, ethylbenzene, and
Fig. 9.8 Surface modification of CNTs and mechanism for adsorption of BTEX on oxidized CNTs
(Lu et al. 2008)
9 Application of Carbon-Based Nanomaterials for Removal of Hydrocarbons
215
behavior of the SWCNTs for o-xylene greatly changed after the purification.
Surface modification of carbon nanotubes has been widely acknowledged as
an effective method to enhance the performance for particular purposes, which
can be easily achieved with different methods (Norzilah et al. 2011; Lu et al.
2008). The maximum adsorption of pollutant on CNTs depends upon pore
structure and oxygen functional groups (-OH, –CO, and –COOH), which depend
upon fabrication and purification methods. Lu et al. (2008) fabricated carbon
nanotubes by the catalytic chemical vapor deposition method and oxidized by
HCl, H 2 SO 4 , HNO 3, and NaOCl solutions for enhancing benzene, toluene, ethylbenzene, and p-xylene (BTEX) adsorption in an aqueous solution. With this
method surface nature of CNTs was changed which makes CNTs that adsorb
more BTEX. The CNT (NaOCl) have the greatest enhancement in adsorption
capacity for BTEX, followed by the CNT(HNO 3 ), CNT(H 2 SO 4 ), CNT, and then
the CNT(HCl). This suggested that the NaOCl oxidized CNTs are efficient BTEX
adsorbents and that they possess good potential applications for BTEX removal in
wastewater treatment. The adsorption mechanism of BTEX on CNTs was also
suggested which is mainly due to the π–π electron donor–acceptor interactions
between the aromatic ring of BTEX and the surface carboxylic groups of CNTs
(Fig. 9.8).
Ji et al. (2010) found that KOH dry etching is a useful activation method for
SWCNTs and MWCNTs to improve the adsorption affinity and adsorption reversibility of organic contaminants on carbon nanotubes. For this study, they chose
monoaromatic compounds (phenol and nitrobenzene) and pharmaceutical antibiotics
(sulfamethoxazole, tetracyclineandtylosin) in aqueous solutions. Yu et al. (2012)
also activated multi-walled carbon nanotubes by KOH (CNTs-KOH) and employed
as adsorbents to study adsorption characteristics of toluene, ethylbenzene, and mxylene (TEX) from aqueous solutions. The maximum adsorption capacities on
CNTs-KOH are 87.12, 322.05, and 247.83 mg/g for toluene, ethylbenzene, and
Fig. 9.8 Surface modification of CNTs and mechanism for adsorption of BTEX on oxidized CNTs
(Lu et al. 2008)
9 Application of Carbon-Based Nanomaterials for Removal of Hydrocarbons
215