Environmental Engineering Reference
In-Depth Information
5
NaNomaterials for the removal
of volatile orgaNic compouNds
from aqueous solutioNs
Amro El Badawy
1
and Hafiz H.M. Salih
2
1
Pegasus Technical Services Inc., Cincinnati, OH, USA
2
Illinois Sustainable Technology Center, University of Illinois at Urbana-Champaign, Champaign, IL, USA
5.1
iNtroductioN
Volatile organic compounds (VOCs) are naturally occurring or man-made hydrocarbons with high saturation vapor pressures
(>102 kPa) at room temperature conditions (25°C) [1]. Examples of VOCs include BTEX (i.e., benzene, toluene, ethylbenzene,
and
p
-xylene), chlorobenzenes, and chlorinated alkenes. Extensive use of VOCs in various industrial processes results in the dis-
charge of large annual amounts of these compounds into the aqueous environment [2]. VOCs are highly reactive and are among
the most toxic chemicals for human health and the environment [1]. Most VOCs are known as carcinogens (i.e., benzene), while
some (toluene, xylenes) are associated with acute effects [3]. Persistent release of toxic VOCs into the aquatic environment is a
growing concern. Therefore, there is great demand to develop novel, cost-effective, and environmentally friendly methods for
their destruction [3].
Many remediation processes such as sorption, redox reactions, and photocatalytic transformations are currently being
improved or initiated by using nanomaterials (NMs) for the removal of organic pollutants from wastewater and drinking
water [4]. For instance, sorption into NMs has proven to be an effective method for the removal of VOCs from aqueous solu-
tion. Carbon nanotubes (CNTs) as well as metal and metal oxide nanoparticles (NPs) have unique properties that make them
more efficient sorbents for the removal of VOCs as compared to traditional sorbent materials. Two key properties that make
NMs attractive sorbents are (i) on a mass basis, NMs have significantly higher surface areas as compared to the bulk species
and (ii) NMs can be functionalized with various types of functional groups to increase their affinity toward target compounds
[5]. Photocatalysis and redox reactions mediated by NPs have also been tested for the decomposition of VOCs present in
aqueous solutions [6, 7]. The current chapter aims to give an overview of the potential uses of NMs for the removal of VOCs
from aqueous solutions.
5.2
Nms for BteX removal
The BTEX VOCs benzene (B), toluene (T), ethylbenzene (E), and
p
-xylene (X) are important solvents commonly used in
industrial operations [2]. A large amount of BTEX wastewater is discharged annually into the aqueous environment, posing
public health and environmental risks [2]. Research studies reported the use of various types of NMs such as CNTs and gold
NP-poly(dimethylsiloxane) (Au-PDMS) nanocomposites for the removal of BTEX from contaminated water [2, 8].
