Page 313 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

298 Environmental Applications of Nanomaterials

Reactive nanoparticles
are injected into a well

Nanoparticles
Contaminant
plume
Contaminant
source

D

NAPL
B
Sand grain

A C
Figure 8.1 The macroscale problem. Illustration of DNAPL distribution as
residual saturation (sources) and a plume of dissolved contaminants in an
aquifer. Nanotechnology offers the potential to effectively target the chemical
treatment to the residual saturation zone in situ. Reactive nanoparticles are
injected into the aquifer using a well. The particles are transported to the con-
taminant source where they can degrade the contaminant. Nanoparticles can
aggregate (A) and be filtered from solution via straining (B) or attachment to
aquifer grains (C). Methods to target the nanoparticles to the contaminant (D)
could improve the efficiency of the technology. Factors affecting the mobility of
nanoparticles in the subsurface and the ability to target contaminants are dis-
cussed later in this chapter.

leaching to the groundwater, resulting in large plumes of dissolved con-
taminants and decades-long remediation times. Often the contaminant
source may be difficult to locate or is too deep for excavation to be a cost-
effective solution, and the prevailing “pump-and-treat” technologies
cannot meet cleanup targets in a reasonable amount of time in most
cases (Water Science Technology Board 2004). “Pump-and-treat” attempts
to remove the contamination by pumping groundwater from the con-
taminated plume to the surface to remove the contaminants. “Pump-and-
treat” and other technologies that address primarily the plume tend to
fail because they do not address or remove the source. Accordingly, the
Department of Energy recently advocated the development of novel
in situ technologies to accelerate the rate at which contaminated sites
are restored back to an acceptable condition (US DOE 2005).