Environmental Engineering Reference
In-Depth Information
nanofiltration technique, coagulation-adsorption-nanofiltration approach (Sarkar et al.,
2007), and nanofiltration-complexation process (Gaubert et al., 1997a; Gaubert, 1997b).
14.4.2 Non-Point Source Pollution Control by Adsorption
Nanomaterials can be anchored onto substrates for the remediation of
contaminated air and water streams by adsorption or absorption processes (Ponder et al.,
2000). For example, carbon, zeolites, silica gel, alumina and membranes, are very
common adsorbents for the treatment of contaminated streams and removals of organics
and heavy metals. Activated carbon is one of the most common adsorbents to solve the
NPS pollution and remove toxic chemicals. Carbon adsorbents in nano-sizes are novel
manufactured materials, having widespread and more highly potential applications. For
example, fullerenes, single-walled carbon nanotubes (SWCNTs), and multiwalled
carbon nanotubes (MWCNTs) were investigated to remove/adsorb polycyclic aromatic
hydrocarbons (PAHs), N 2 , benzene, methanol, among other contaminants
(Eswaramoorthy et al., 1999; Yang et al., 2006; Cho et al., 2008; Sun, 2008;).
Adsorption behaviors of n-hexane, benzene, trichloroethylene, toluene, methyl
ethyl ketone (MEK), super greenhouse gas (Tetrafluoromethane), cyclohexane and
acetone on MWCNTs have been investigated (Long and Yang, 2001; Liu et al., 2004;
Agnihotri et al., 2005; Crespo and Yang, 2006; Lu and Su 2007; Shim et al., 2007;
Kowalczyk and Holyst, 2008; Shih and Li, 2008). The morphological and structure order
of carbon nanotubes (CNTs) are the primary factors affecting the adsorption process of
organic chemicals.
Except adsorption of volatile organic compounds (VOCs), CNTs have also been
employed to remove pollutants and metal ions from water, like trihalomethanes (THMs)
(Lu et al., 2005), atrazine (Yan et al., 2008), Pb(II) (Rao et al., 2007; Wang et al., 2007).
The Pb(II) species adsorbed on acidified MWCNTs mainly aggregate on the end of and
at the defects sites on the acidified MWCNTs.
The adsorption of organic compounds to SWCNTs and MWCNTs correlates
with varied physical-chemical properties (e.g., hydrophobicity, polarity, electron
polarizability, size) (Chen et al., 2007). The adsorption affinity related poorly with
hydrophobicity but increased in the order of nonpolar aliphatic < nonpolar aromatics <
nitroaromatics. For the nitroaromatics, the adsorption affinity increased with the number
of nitro-groups. The strong adsorptive interaction between CNTs and aromatics may be
due to the - electron-donor-acceptor interaction between aromatic molecules (
electron acceptors) and the graphene sheets ( electron donors) of CNTs.
Iron nanoparticles are increasingly being used as adsorbents for various types of
organic and inorganic pollutants. NZVI is also a suitable adsorbent for the removal of
 
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