Biomedical Engineering Reference
In-Depth Information
Kim et al. [39] have demonstrated the ability of ferritin to reduce hexava-
lent chromium, a dangerous carcinogen, to the chromium trivalent form,
which is ubiquitous and less toxic. The researchers also expect to test the
new technology on nuclear contaminants [39]. If proven applicable, this tech-
nology can be used to remediate groundwater that has been contaminated
from the leakage of storage canisters containing nuclear waste [40]. The tech-
nology also offers potential remedial capabilities for aromatics and chloro-
carbons [25].
7.4.1.5 Single-Enzyme Nanoparticles
Enzymes have been proven more effective than synthetic catalysts in many
areas of application. However, owing to their chemical instability and rela-
tively short lifetimes, they are considered inappropriate to apply for envi-
ronmental remediation. A new method of enzyme stabilization has recently
been developed, which involves the production of environmentally persis-
tent single enzyme NPs (SENs) [41].
SENs are resistant to extreme conditions such as high/low pH, high con-
taminant concentration, high salinity, and high/low temperature. They are
generally much easier to control than microbial organisms. They need no
nutrients to exist and any metabolic by-products or mass transfer limitations,
due to cellular transport, are avoided [41].
Specific enzymes are used for the different contaminants. Some examples
of enzyme classes appropriate for remediation are the peroxidases, polyphe-
nol oxidases (laccase, tyrosinase), dehalogenases, and organophosphorus
hydrolases [42]. The great choice of applicable enzymes implies the possi-
bility for successful remediation of a broad range of organic contaminants
in water. Contaminants such as phenols, polyaromatics, dyes, chlorinated
compounds, organophosphorus pesticides, and even explosives can be suc-
cessfully degraded using appropriate enzymes [41].
7.4.1.6 Summary and Conclusions
Environmental remediation nanotechnology is still in its infancy, but, rap-
idly evolving, it holds promise to clean contaminated sites cost-effectively
and address challenging site conditions, such as the presence of DNAPL.
The most important example described in this chapter is the nZVI, which
has been used in full-scale projects with encouraging success. As a cleanup
technology, it has three major advantages: (1) effective for the transforma-
tion of a large variety of environmental contaminants, (2) inexpensive, and
(3) apparently nontoxic [24].
Similarly to nZVI, nanoparticulate TiO
2
has been widely used in environ-
mental remediation because of its low toxicity, high photoconductivity, high
photostability, availability, and low cost [25,30]. The TiO
2
-based p-n junction
