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PLASMAS ATOMISE TOXIC WASTES
5 May 2000

The Academy of Science’s Pawsey Medal has been awarded to a physicist at CSIRO Telecommunications and Industrial Physics in Sydney, Dr Tony Murphy, 40. Dr Murphy is a brilliant young scientist who has applied his knowledge of plasma physics to the environmental problem of hazardous chemical disposal.

Ten years ago high-temperature incinerators were seen as the best means of destroying hazardous chemicals. But these were large and costly, and no-one wanted an incinerator in their backyard. Proposed remote locations would have required the chemicals to be transported long distances.

In the last few years a team of CSIRO scientists in Sydney and Melbourne has built small units that use plasmas to destroy hazardous chemicals. The intense heat of the plasmas (10,000 degrees Celsius) breaks the chemicals down more rapidly than incinerators, into their constituent atoms. Placing the units near collection points solves the transport problem.

Plasmas are hot clouds of ionised gas. Dr Murphy has performed developed new theoretical methods that allow him to model the way the particles in a plasma move and interact with other particles, and used sophisticated laser techniques to confirm his predictions. His understanding of the chemistry and fluid dynamics of plasmas has helped him improve the chemical destruction process. Problems occurred when the destruction of some ozone-depleting chemicals (chlorofluorocarbons and halons) produced other undesirable chemicals. Dr Murphy and his colleagues worked out ways to manipulate the plasma, particularly how to feed in the waste chemical, so that unwanted by-products were not produced. Without his fundamental knowledge of physics, it would not have been possible to solve these practical problems.

In a collaboration between CSIRO and SRL Plasma, a subsidiary of Siddons-Ramset Ltd, four plants have been built in Melbourne and Brisbane. They are used to destroy the waste product of the manufacture of 2,4 D (a weedkiller), polychlorinated biphenyls (used in electricity transformers), and ozone-depleting chemicals. The technology is a potential export product.

Dr Murphy has also applied his knowledge to improve our understanding of welding (the welding arc is a plasma). He is now working on ways to make ozone with plasmas. Ozone purifies water better than chlorine and breaks down quickly. The ozone-generators would be used to purify the water in swimming pools, in small sewerage works, in cooling towers, and for the farming and food processing industries

The Pawsey Medal is awarded each year to a younger scientist who has carried out distinguished research in physics. Earlier Pawsey medallists, such as the new President of the Royal Society, Sir Robert May, are now internationally recognised leaders in science.