Iodide uptake by negatively charged clay interlayers?

Andrew Miller, Jessica Kruichak, Melissa Mills, Yifeng Wang

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Understanding iodide interactions with clay minerals is critical to quantifying risk associated with nuclear waste disposal. Current thought assumes that iodide does not interact directly with clay minerals due to electrical repulsion between the iodide and the negatively charged clay layers. However, a growing body of work indicates a weak interaction between iodide and clays. The goal of this contribution is to report a conceptual model for iodide interaction with clays by considering clay mineral structures and emergent behaviors of chemical species in confined spaces. To approach the problem, a suite of clay minerals was used with varying degrees of isomorphic substitution, chemical composition, and mineral structure. Iodide uptake experiments were completed with each of these minerals in a range of swamping electrolyte identities (NaCl, NaBr, KCl) and concentrations. Iodide uptake behaviors form distinct trends with cation exchange capacity and mineral structure. These trends change substantially with electrolyte composition and concentration, but do not appear to be affected by solution pH. The experimental results suggest that iodide may directly interact with clays by forming ion-pairs (e.g., NaI(aq)) which may concentrate within the interlayer space as well as the thin areas surrounding the clay particle where water behavior is more structured relative to bulk water. Ion pairing and iodide concentration in these zones is probably driven by the reduced dielectric constant of water in confined space and by the relatively high polarizability of the iodide species.

Original languageEnglish (US)
Pages (from-to)108-114
Number of pages7
JournalJournal of Environmental Radioactivity
Volume147
DOIs
StatePublished - Sep 1 2015

Fingerprint

iodide
Iodides
Clay
Clay minerals
clay
Minerals
clay mineral
Confined Spaces
Electrolytes
Water
Ions
Radioactive wastes
Chemical analysis
Waste disposal
electrolyte
Ion exchange
Permittivity
Substitution reactions
mineral
Positive ions

Keywords

  • Clay minerals
  • Ion pairing
  • Nuclear waste
  • Radioiodine

ASJC Scopus subject areas

  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution
  • Health, Toxicology and Mutagenesis

Cite this

Iodide uptake by negatively charged clay interlayers? / Miller, Andrew; Kruichak, Jessica; Mills, Melissa; Wang, Yifeng.

In: Journal of Environmental Radioactivity, Vol. 147, 01.09.2015, p. 108-114.

Research output: Contribution to journalArticle

Miller, Andrew ; Kruichak, Jessica ; Mills, Melissa ; Wang, Yifeng. / Iodide uptake by negatively charged clay interlayers?. In: Journal of Environmental Radioactivity. 2015 ; Vol. 147. pp. 108-114.
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