Biomedical Engineering Reference
In-Depth Information
nanotubes represent a recent innovation in the field of nSPs. They exhibit
higher decontamination rates than nonnanotube materials [33], and as their
production cost falls they may become the next generation of nSPs.
Ongoing research at the bench- and pilot-scale investigates technologies
such as ferritin-encapsulated iron oxides and polymeric and the single-
enzyme NPs to determine how to apply their unique characteristics for full-
scale remediation. Despite the fact that these technologies deliver no current
benefits for the environment, some of them may contribute to environmental
remediation at a later stage.
Unfortunately, no quantitative comparison among the costs of application
of nano-based remedial tools and their conventional counterparts could be
accurately conducted at this time. The reason is that the factors that con-
tribute to the costs of remediation are not only technology specific but also
site and contaminant specific, and the remediation cost data in the litera-
ture are incomplete. Qualitatively, the vast majority of publications state that
nZVI and TiO
2
are more cost-effective than their conventional counterparts.
Being cheaper and more effective, these technologies will gradually become
more widely used and will have significant impact on the future remediation
activities.
Despite the dominating predictions that remedial nanotechnologies will
deliver significant benefits, there are still many unanswered questions
regarding their toxicity. Further research is needed to understand the fate
and transport of free NPs in the environment to study their persistence and
their potential to bioaccumulate and cause adverse effects in animals and
humans.
7.4.2 Treatment Nanotechnologies
Nanofiltration is a relatively recent membrane process that holds promise to
deliver cost-effective water and air treatment solutions. “Nanofiltration” as a
term was coined several years ago to define already used membranes, called
at the time “loose reverse osmosis membranes.” Other separation processes
similar to nanofiltration are the reverse osmosis, ultrafiltration, microfiltra-
tion, and particle filtration. The main difference among these processes is
the metric scale at which they operate (i.e., the size of particles they are able
to retain). Table 7.3 compares the four processes in terms of (1) pore size,
(2) materials used to construct the membranes, and (3) type of removed
contaminants.
Nanomembranes (NMs) are used not only to remove contaminants from
polluted water and air but also for desalination of salty water. There are two
types of NMs currently available on the market: nanofilters, using either
carbon nanotubes (CNTs) or nanocapillary arrays to mechanically remove
impurities, and reactive NMs, where functionalized NPs chemically convert
the contaminants into safe by-products.
