Project Summary (1995-2000)

In this project methods are being developed for applying a semiconductor/macrocycle hybrid system and for an electrolytic cell that uses elemental iron as cathode for promotion of in situ reductive dehalogenation reactions under field conditions. These systems have already proven to be much faster than bacteria for catalysis of dehalogenation reactions. During the first part of the project, the semiconductor (with covalently attached macrocycle) is being fixed to the exposed surface of a fiber optic line and harvesting evanescent wave energy. This configuration serves as a means of transmitting light energy to the catalysis underground. In the second part of this project, an electrolytic reactor in which iron wool is used as a fixed-potential cathode is being developed for reductive dehalogenation of heavily halogenated environmental contaminants. If successful, such a reactor could be used to treat contaminated aquifers without bringing water to the surface. It should be possible to maximize the rate of the desired reaction while maintaining undesirable side reactions at modest levels. The system under development has the additional benefit of liberating little or no free metal during the dehalogenation reaction, an ideal trait from the perspective of in situ applications. The effectiveness of components of the elemental metal/fixed-potential system for promoting dehalogenation reactions under laboratory conditions has already been established. Continued studies of Shewanella putrefaciens as a model bacterial system for reductive dehalogenation reactions will also be pursued.