Releasing radionuclides of iodine (e.g., 131I) into the atmosphere presents a major concern during a nuclear emergency such as the Fukushima incident in 2011. Iodine’s affinity for the thyroid gland makes radioiodine a significant, health concerning, biological hazard and necessitates important efforts to minimize its discharge into the atmosphere. Activated carbon, impregnated with KCl or DABCO (1,4-diazabicyclo[2.2.2]octane), routinely provides the means to hold up iodine-containing molecules and mitigate their release. The interactions between activated carbon and inorganic forms of iodine remain poorly understood. Using graphite or graphene as a surrogate for activated carbon, previous studies have analyzed the adsorption behavior of methyl iodide. However, these studies ignore the adsorption of acidic iodine species (e.g., HI, HOI, HIO2, and HIO3) on activated carbon. We present a density functional theory analysis of the adsorption of these molecules on the basal (0001) plane of graphite. Characterizing the preferred adsorption sites, geometries, and binding mechanisms for these molecules on pristine graphite further clarifies the species that are most easily captured. We compare the binding energies between other common species to assess how reactive the surface is for the iodine-containing molecules. Additionally, we analyze the co-adsorption and select surface reactions between the most likely surface species. These effects help us predict the speciation of iodine on the surface and its influence on the molecules likely to be released from the activated carbon bed. Our computational analysis provides insights that will aid in the future design of capture materials based on activated carbon beds for the purpose of mitigating release of radioiodine into the atmosphere during a nuclear disaster.

Density functional theory analysis of the adsorption and surface chemistry of inorganic iodine species on graphite

2019 Fall National Meeting

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