Strontium speciation during reaction of kaolinite with simulated tank-waste leachate: Bulk and microfocused EXAFS analysis

Sunkyung Choi, Peggy A. O'Day, Nelson A. Rivera, Karl T. Mueller, Murthy A. Vairavamurthy, Supapan Seraphin, Jon Chorover

Research output: Contribution to journalArticle

30 Scopus citations

Abstract

Radioactive strontium (90Sr) is an important constituent of the complex wastes from past nuclear weapons production and has been stored in underground tanks at U.S. DOE sites (e.g., Hanford, WA). Using bulk and microfocused EXAFS spectroscopy, we examined temporal changes in solid-phase Sr speciation in kaolinite samples reacted for 1-369 d with high-pH, high ionic strength synthetic tank-waste leachate containing Sr2+ and Cs + at 10-3 mol kg-1. Analyses of bulk EXAFS spectra showed that Sr initially forms a precipitate by 7 d with a local structure similar to SrCD3-(s). At 33 d, microfocused EXAFS of individual particles in one sample revealed a mixture of hydrated and dehydrated Sr associated with neoformed sodalite-type phases. At aging times of 93 d and longer, bulk EXAFS spectra and supporting characterizations indicated nonexchangeable Sr with a local structure consistent with incorporation into increasingly crystalline aluminosilicate particles, particularly sodalite. These experimental studies suggest that irreversible trapping of radionuclides occurs if they are present during the formation and aging of feldspathoid alteration products of local Si-bearing sediment minerals. This may serve as an effective contaminant sequestration mechanism at sites such as Hanford.

Original languageEnglish (US)
Pages (from-to)2608-2614
Number of pages7
JournalEnvironmental Science and Technology
Volume40
Issue number8
DOIs
StatePublished - May 15 2006

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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