BY-PRODUCT FORMATION DURING THE REDUCTION OF TCE BY ZERO-VALENCE IRONAND PALLADIZED IRON

Trichloroethene (TCE) was reduced with zero-valence iron and palladize d iron in zero-head-space extractors. Progress of the reaction in thes e batch studies was monitored with purge-and-trap gas chromatography a nd a flame ionization detector. When a 5 ppm initial concentration of TCE reacts with zero-valence iron, approximately 140 ppb of vinyl chlo ride persists for as long as 73 days. The concentration of vinyl chlor ide (approximately 10 ppb) remaining with palladized iron is approxima tely an order of magnitude less than when zero-valence iron is the red uctant. These data suggest that volatile byproducts may be underrepres ented in other published data regarding reduction with zero-valence me tals. These results also demonstrate that the reduction of TCE with pa lladized iron (0.05 percent palladium) is more than an order of magnit ude faster than with zero-valence iron. With a 5:1 solution-to-solid r atio the TCE half-life with zero-valence iron is 7.41 hours, but is on ly 0.59 hours with the palladized iron.