Byproduct formation during the reduction of TCE by zero-valence iron and palladized iron

Trichloroethene (TCE) was reduced with zero-valence iron and palladized iron in zero-head-space extractors. Progress of the reaction in these batch studies was monitored with purge-and-trap gas chromatography and a flame ionization detector. When a 5 ppm initial concentration of TCE reacts with zero-valence iron, approximately 140 ppb of vinyl chloride persists for as long as 73 days. The concentration of vinyl chloride (approximately 10 ppb) remaining with palladized iron is approximately an order of magnitude less than when zero-valence iron is the reductant. These data suggest that volatile byproducts may be underrepresented in other published data regarding reduction with zero-valence metals. These results also demonstrate that the reduction of TCE with palladized iron (0.05 percent palladium) is more than an order of magnitude faster than with zero-valence iron. With a 5:1 solution-to-solid ratio the TCE half-life with zero-valence iron is 7.41 hours, but is only 0.59 hours with the palladized iron.