Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 40, Issue 21, Pages 6837-6843Publisher
AMER CHEMICAL SOC
DOI: 10.1021/es060921v
Keywords
-
Categories
Ask authors/readers for more resources
Bimetallic reductants are frequently more reactive toward organohalides than unamended iron and can also alter product distributions, yet a molecular-level explanation for these phenomena remains elusive. In this study, surface characterization of six iron-based bimetallic reductants (Au/Fe, Co/Fe, Cu/Fe, Ni/Fe, Pd/Fe, and Pt/Fe) revealed that displacement plating produced a non-uniform overlayer of metallic additive on iron. Batch studies demonstrated that not all additives enhanced rates of 1,1,1-trichloroethane (1,1,1-TCA) reduction nor was there any clear periodic trend in the observed reactivity (Ni/Fe approximate to Pd/Fe > Cu/Fe > Co/Fe > Au/Fe approximate to Fe > Pt/Fe). Pseudo-first-order rate constants for 1,1,1-TCA reduction (k(obs) values) did, however, correlate closely with the solubility of atomic hydrogen within each additive. This suggests absorbed atomic hydrogen, rather than galvanic corrosion, is responsible for the enhanced reactivity of bimetallic reductants. In addition, all additives shifted product distributions to favor the combined yield of ethylene plus ethane over 1,1-dichloroethane. In rate-enhancing bimetallic systems, branching ratios between 1,1-dichloroethane and the combination of ethylene and ethane were uniquely dependent on k(obs) values, indicating an intimate link between rate-determining and product-determining steps. We propose that our results are best explained by an X-philic pathway involving atomic hydrogen with a hydride-like character.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available