Scientists at the University of Texas, US, are attempting the use of electrochemical and photochemical methods to purify polluted water. Apart from being inexpensive, these methods save the user the bother of treating the purifying agents used as catalysts in the process
RESEARCHERS from-the department of
chemistry and biochemistry at the
University of Texas in Arlington, US,
have developed an inexpensive method
of combating water pollution by using
sunlight in combination with catalysts.
The department has also developed a
technique to tackle chromium pollution
using a conducting polymer called
polypyrrole. According to the researchers, not only are these methods cheap
and energy efficient, but also do not
pose the problem of disposal of the
agent used in the treatment of water.
The scientists believe that the very idea
of using electrochemical treatment is to
avoid the substitution of one chemical
with the water. For instance, freon, an
ozone depleting substance (CIDS), will be
broken down to hydrochloric acid and
thereafter to water and carbon dioxide.
The titanium dioxide (Tio2) technique, a photochemical treatment in
which TiO2 is used as a catalyst, can be
used for both organic and inorganic
pollutants. It involves the absorbtion of
light and generates hydroxyl radicals.
When these radicals - highly reactive
and oxidising as they are - come in
contact with organic molecules, they
break them up.
For treating chromium pollution
using conducting polymers, the method
used is based on redox chemistry.
When light hits particles of the catalyst,
electrons are created. Their generation
immobolises the pollutant and reduces
them. For example, the highly polluting
chromium 6+ (Cr 6+) is converted to
more harmless Cr 3+. Basically, what
happens is that the polymer, on coming
in contact with the pollutant, transfers
its electrons to the latter. Thus the pollutant gets reduced and the polymer is
oxidised. This polymer can then be
recycled and reused.
Krishnan Rajeshwar from Texas
University gave the details of these
techniques during the recently held
international conference on environmental science organised by the
Regional Research laboratory (RRL),
Thiruvananthapuram. The RRL is also
carrying out a quality assurance
programme for the department of
ocean development's coastal ocean
monitoring and predictive systems
programme. Kenneth H Coale of
Moss Landing Marine Laboratories,
California, us, spoke about the development of in situ shipboard and shore-based methods for the determination of
trace elements and nutrients in sea
water. In an experiment near the
Galapagos islands, these methods have
been applied to study the distribution of
trace metals in oceans, iron and
manganese in hydrothermal plumes,
long-term chemical sensing of nitrate
from a moored chemical analyser and
the mapping of iron. The unique feature
of these projects is that the tests are
done underwater and the results are
transmitted through wires to the ship
or shore.
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