Jumping into a nano blue land
Different technologies has been
implemented to make water consumption more efficient and available in a world
where almost 1 billion people still have no access to this blue gold and other
millions die because of contaminated water.
Scientists started looking for solutions
at the “bottom”of the materil, at atom level, jumping into
nano-demantion land.First of all nanoparticles did not come
out in these decades as it may seem but they have a long history. Nanoparticles ante litteram was already
exploited by Roman artisans in IV century,
and during the Middle Ages master glaziers included small amount of
metal oxide to make amazing colorful glass wall. But only at the end of XX
century scientific researches and the development of sophisticated
instruments like STM (Scanning Tunnelling Microscope) made possible the comprehension
about the properties of nanoparticles and their handling.
Nowadays particular nano structures built
with a specific chemical and structural conformations are being more and more
studied, from the nanoshells or golden nano particles as non invasive treatment agaist cancer in
the devopling field of nanomedicine to
new nano materials used in energy engineering; we have a great list but let’s
focus on what concerns our topic.
It is well known the story of Graphene, a one-atom thick layer of graphite, made of only carbon
atoms that are densely packed in a regular sp2-bounded
atomic hexagonal pattern. This 2-dimantional
nano strucure is
remarkably strong for its very low weight (100 times stronger than steel), it
conducts heat and electricity efficiently, it is the basic strucure element for
nanotubes and fullerenes and because of
its significant properties it has been subject of increasing number of
researches and studies. At MIT , for instance, Jeffrey C.
Grossman, an associate professor of power engineering, and his graduate
students David Cohen-Tanugi and Shreya Dave are developing a filtration
material made of a sheet of nanoporous graphene. The holes in the graphene are
small enough to block salt ions while letting water molecules through. This is a process of desalination
that applays reverse osmosis principle, which relies on semipermeable membranes
to filter salt from water. But such systems demand high pressure to force water
( agaist osmosis) through the membranes which are about a thousand times thicker than ones made of graphene. Moreover graphene is 500 more permeable.
Another study conducted by Jin-Woo Kim at the University of Arkansas has tested the effectivness of
multi-walled carbon nanotubes (MWNT) , smooth pipes of water-repelling graphite, in cleaning contaminated water. Keeping it simple, by exploiting the magnetic susceptibility and bacterial affinity of
nanotubes pathogenes are captured and enbodied in MWNTs cluster, then separetad
from water through an external magnet.
Conventional purification methods such as
chlorination, standard filtration, UV radiation, and the infusion of water with
ozone gas, aren’t that cheap, nor are they always practical for developing
countries therefore the challenge
is to make the purification process more efficient, affordable, and
available to more people through nanotechnology.
At this link you can see a reasonalble
cheap nanofilter realized using peculiar
properties of nanoparticles http://www.scientificamerican.com/article/cheap-nanotech-filter-water/
If you want to have a general view and to
know more about nanotech and this
fascinating nanoworld an easy but complete and well written, though only in
italian, book that I can suggest is “ Quanto è piccolo il mondo”by Gianfranco
Pacchioni.
Fei Fei