United States Environmental Protection Agency National Risk Management Research Laboratory Cincinnati, OH 45268 Research and Development EPA/600/SR-98/124 September 1998 EPA Project Summary Substitution Reactions for the Detoxification of Hazardous Chemicals Fred K. Kawahara Recent literature on substituting chemical reagents that will convert toxic halogenes to their nontoxic hydrocar- bons was surveyed. Within this cat- egory of chemical substitution, three types of reactions are discussed: su- peroxide ion radical reactions, polyeth- ylene glycol (PEG) transformations of PCBs, and catalytic hydrogen transfer reactions. This Project Summary was developed by EPA's National Risk Management Research Laboratory, Cincinnati, OH, to announce key findings of the re- search project that is fully documented in a separate report of the same title (see Project Report ordering informa- tion at back). Background Chemical substitution is one of several techniques available to treat hazardous chemicals that can threaten the environ- ment. In the report, briefly summarized here, chemical treatment is substituting hydrogens for halogens so as to convert the halogenated organics to hydrocarbons or to mineralize the organic to carbon dioxide, water, or other components). Three types of reactions applicable to the conversion of hazardous chlorohy- drocarbons to their respective nontoxic hydrocarbons are discussed: • superoxide ion radical reactions, • dehalogenation of polyhaloaromatics and polyhaloalkanes with PEGs; and • catalytic hydrogen transfer reactions. Some fundamental aspects of these re- actions are reported. With O2 representing molecular oxygen, a one-electron reduction in its valence yields the ion radical O2 —. Studies are cited that demonstrate reactions caused by this superoxide ion radical, e.g., PCS oxygenation. Use of PEG, together with a base such as potassium hydroxide, has been found to be a promising technique. On reporting on processes involving PEG'S use, how PEG functions as the reactive agent to dechlorinate PCB is developed. With the catalytic transfer hydrogena- tion reactions, organic acceptor molecules are catalytically reduced with hydrogen donated by another organic molecule. The literature review of catalytic transfer hy- drogenation is restricted to certain reac- tion conditions and solvent effects and to some details in molecular donor and ac- ceptor structures. Studies on the effects of temperature, solvents, solvents in het- erogeneous systems, homogeneous ca- talysis, and heterogeneous catalysis on transfer reductions are included. The full report is a valuable survey of recent literature (incorporating almost 100 citations) on this subject; it is not intended as a manual on technical application. Printed on Recycled Paper ------- The EPA author, Fred K. Kawahara, is with the National Risk Management Research Laboratory, Cincinnati, OH 45268. The complete report, entitled "Substitution Reactions for the Detoxification of Hazardous Chemicals," (Order No. PB98-177876; Cost: $25.50, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-605-6000 The EPA author can be contacted at: National Risk Management Research Laboratory U.S. Environmental Protection Agency Cincinnati, OH 45268 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati, OH 45268 Official Business Penalty for Private Use $300 BULK RATE POSTAGE & FEES PAID EPA PERMIT No. G-35 EPA/600/SR-98/124 ------- |