Nanoparticles: how should we picture them?
That's not easy, because nanoparticles are invisible
to the naked eye. The head of a needle is as large as
a million nanoparticles. To be precise: they are between
one and ten billionths of a metre in diameter. Which
isn't big.
So how can a particle so small still be useful?
The strength of nanoparticles is precisely the fact
that they are so small. Doctors use nanoparticles to
transport medication to the right place in the body, and
electrical engineers use nanotechnology to develop even
smaller computer chips. In addition, this technology
is relatively cheap because you can make very large
numbers of nanoparticles with little material. And
that is another advantage that makes this technology
particularly appealing.
Nanotechnology for cleaning up soil: how does
that work?
Nanoparticles can reach places that are often
inaccessible using current remediation technologies.
The nanoparticles react with the contaminants, forming
harmless substances, or stop the pollution spreading
further. Soil clean-up work often involves using
processed iron. Iron is naturally present in the soil
and is not toxic in itself.
That sounds very promising. Is it really?
It certainly is. This technology can be used to tackle
types of pollution that are still difficult to treat using
current technologies. Such as certain types of contami
nation that do not dissolve completely in water but
that persist in the soil in drop form, or for fixing arsenic
and toxic metals. It is also a much faster method than
those currently available, making it cheaper once again.
One of the standard methods involves pumping up
contaminated water, which is then pumped back into
the ground after it has been cleaned up. That can take
years, and sometimes decades. Nanotechnology can
clean up pollution where it occurs, eliminating the need
for pumping. We are talking about a few months.
So why is nanotechnology still used so little?
The technology still needs to be improved. The
nanoparticles are pumped into the soil using pipes,
and they then spread. A fewmetres away from the
pipe, the particles coagulate and don't spread any
further. As a result, large numbers of pipes have to be
installed to clear upmore extensive pollution. One solution
could be to make a change to the nanoparticles to stop
them coagulating but that could result in the particle
losing its useful properties. And we still need to establish
a full picture of the risks associated with the method.
Risks? What's the story there?
In theory, the risks would seem to be minimal but more
research is needed. For example, what happens when
the nanoparticles spread outside the polluted location?
We can only go to work when we have answered
questions like this satisfactorily.
How unfortunate. Can we expect to see
nanotechnology being used in soil remediation?
Certainly, and it probably won't take long. At the
moment, the possibilities and risks associated with
nanotechnology in the field of soil remediation
are being explored in greater detail in the NanoRem
(
project. This project is also looking
for ways of applying the technology on a large scale
while minimising costs. The NanoRem project will be
completed in late 2017. The technology will already
have been used in a number of locations by then.
Nanoparticles are a promising, cost-saving
technology generally, but also in soil remediation.
Research in this area is in full swing and the technology
will probably be available soon. But what are
these nanoparticles, how do they work,
and do they involve risks?
BY KARIN STONE
HOW THIS
MINUSCULE PARTICLE
CAN CLEAN UP
YOUR SOIL
DELTARES , SEPTEMBER 2014
19
18
PHOTO: THINKSTOCK
Source:
Majid Hassanizadeh, professor of hydrogeology
at the Geosciences Faculty of Utrecht University and senior
consultant for the Deltares Subsurface and Groundwater
Systems department.
For more information:
Pauline van Gaans, senior expert in
Soil Quality & Management,
