Electrifying presence

RESEARCHERS from-the department ofchemistry and biochemistry at theUniversity of Texas in Arlington, US,have developed an inexpensive methodof combating water pollution by usingsunlight in combination with catalysts.The department has also developed atechnique to tackle chromium pollutionusing a conducting polymer calledpolypyrrole. According to the researchers, not only are these methods cheapand energy efficient, but also do notpose the problem of disposal of theagent used in the treatment of water.The scientists believe that the very ideaof using electrochemical treatment is toavoid the substitution of one chemicalwith the water. For instance, freon, anozone depleting substance (CIDS), will bebroken down to hydrochloric acid andthereafter to water and carbon dioxide.

The titanium dioxide (Tio2) technique, a photochemical treatment inwhich TiO2 is used as a catalyst, can beused for both organic and inorganicpollutants. It involves the absorbtion oflight and generates hydroxyl radicals.When these radicals - highly reactiveand oxidising as they are - come incontact with organic molecules, theybreak them up.

For treating chromium pollutionusing conducting polymers, the methodused is based on redox chemistry.When light hits particles of the catalyst,electrons are created. Their generationimmobolises the pollutant and reducesthem. For example, the highly pollutingchromium 6+ (Cr 6+) is converted tomore harmless Cr 3+. Basically, whathappens is that the polymer, on comingin contact with the pollutant, transfersits electrons to the latter. Thus the pollutant gets reduced and the polymer isoxidised. This polymer can then berecycled and reused.

Krishnan Rajeshwar from TexasUniversity gave the details of thesetechniques during the recently heldinternational conference on environmental science organised by theRegional Research laboratory (RRL),Thiruvananthapuram. The RRL is alsocarrying out a quality assuranceprogramme for the department ofocean development's coastal oceanmonitoring and predictive systemsprogramme. Kenneth H Coale ofMoss Landing Marine Laboratories,California, us, spoke about the development of in situ shipboard and shore-based methods for the determination oftrace elements and nutrients in seawater. In an experiment near theGalapagos islands, these methods havebeen applied to study the distribution oftrace metals in oceans, iron andmanganese in hydrothermal plumes,long-term chemical sensing of nitratefrom a moored chemical analyser andthe mapping of iron. The unique featureof these projects is that the tests aredone underwater and the results aretransmitted through wires to the shipor shore.