Electrifying presence

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

Last Updated: Saturday 04 July 2015

-- (Credit: Vishwajyoti)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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