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The Exploration of Conditions in Which Chlorinated Benzenes Are Degraded by Zero-Valent Iron

Shawn Moderow and Danny D. Reible. University of Texas, EWRE C1786, Austin, TX 78712

Chlorinated benzenes are often found as a sediment contaminant due to their bioaccumulation and persistence in the environment. The have a long history in the production of organic compounds and formed from the byproducts of organic chemicals. This study was designed to explore the fate of chlorinated benzenes during capping of the contaminated sediments, specifically the fate associated with zero-valent iron in an active capping layer. The chemical thermodynamics indicate that reductive dechlorination with zero-valent iron is possible but past studies have shown mixed results.. It has been shown that hexachlorobenzene could be dechlorinated successfully with zero-valent iron at a pH of 3 within 48 hours (Lu et al, 2004). Other studies have shown limited reactivity over times scales and conditions more relevant to sediment capping. It has also been suggested that nano scale iron particles could work effectively due to their large surface areas and high surface reactivity (Zhang et al., 2003). Similarly bimetallic systems demonstrated transformation of hexachlorobenzene to tetra-, tri- and dichlorobenzene within 24 hours (Xu and Zhang, 2000). In this paper, experiments exploring degradation of chlorinated benzenes with zero-valent iron and the potential for zero-valent iron as an active cap material to encourage dechlorination under conditions relevant to capping will be discussed.