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A superoxide way to get rid of PCBs.

A superoxide way to get rid of PCBs

The large family of chemical compounds known as poly- chlorinated biphenyls (PCBs) has a reputation for toxicity. Once used as nonflammable, heat-dissipating, insulating liq- uids in transformers and other electrical devices, these oily substances are no longer manufactured. Left behind, however, is the problem of safely cleaning up, degrading or destroying the large quantities of these noxious materials that were generated in the past (SN:9/5/87, p.154). Recently, a team of chemists at Texas A&M University in College Station happened upon a chemical reaction that efficiently converts PCBs and related compounds into sodium bicarbonate and sodium chloride. The unexpectedly complete chemical degradation shown by this reaction makes it a possible alternative to methods such as incineration for disposing of PCBs.

The new chemical reaction, discovered by Donald T. Sawyer and his colleagues, uses superoxide ions to convert the PCBs. Each superoxide ion can be thought of as an oxygen molecule, made up of two oxygen atoms, with an extra electron to give the ion a negative charge. Cosmic radiation creates superoxide ions in the upper atmosphere, and biological processes generate these ions during respiration. In the laboratory, superoxide ions can be generated in electrochemical cells.

One big advantage of the process is taht it seems likely to work on any scale-in small batches or in large loads. The reaction is also highly selective, reacting only with PCBs and their relatives, even when they happen to be mixed with other hydrocarbons. However, superoxide ions also react readily with water. Any reactins involving the ions must be done in nonaquenous solvents, and PCB samples must be kept dry. The new reaction is described in the Dec 23 journal of the AMERICAN CHEMICAL SOCIETY.
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Title Annotation:convert the toxic to sodium bicarbonate and sodium chloride
Publication:Science News
Date:Feb 6, 1988
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