| Abstract
| - Halogenated synthetic compounds are widespreadcontaminants of the environment. Although corrinoidsreductively dehalogenate synthetic contaminants in solution,the redox behavior of sorbed tetrapyrroles has receivedlimitedattention. Colloidal clay suspensions were preparedasCa2+ forms of hectorite (SHCa-1), montmorillonite (SWy-1,Syn-1, and SAz-1), and vermiculite (VTx-1) and spin coatedon platinum electrodes. Cyclic voltammetry wasperformedwith the clay-modified electrodes immersed in bufferedsolutions containing 1.0 mM aquocobalamin.Aquocobalaminin the presence of vermiculite-coated electrodes displayedthe same cathodic and anodic peak potentials asunmodified electrodes immersed in aquocobalamin solutions.All other clay-modified electrodes shifted cathodicpeaksto more negative values, while anodic peak shifts variedwith the clay. Hectorite caused the largest shift informalredox potential (−104 mV) as compared to aquocobalaminin solution. The redox behavior of aquocobalamin asmodified by sorption to clay minerals potentially affectsdehalogenation rates of synthetic organic compounds in theenvironment. Clays lowering the formal redoxpotentialof the tetrapyrrole create a potentially more efficientcatalystfor pollutant degradation. However, thermodynamicdataas obtained using cyclic voltammetry cannot be used tomake definitive predictions about the kinetics of contaminant dehalogenation. Reductive dehalogenation willbe a function of altered eletrochemical properties of thetetrapyrrole as well as rates of contaminant diffusion tothesite of tetrapyrrole sorption.
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