Strontium Speciation during Reaction of Kaolinite with Simulated Tank-Waste Leachate: Bulk and Microfocused EXAFS Analysis

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• 作者：Sunkyung Choi ; Peggy A. O'Day ; Nelson A. Rivera ; Karl T. Mueller ; Murthy A. Vairavamurthy ; Supapan Seraphin ; and Jon Chorover
• 刊名：Environmental Science & Technology
• 出版年：2006
• 出版时间：April 15, 2006
• 年：2006
• 卷：40
• 期：8
• 页码：2608 - 2614
• 全文大小：356K
• 年卷期：v.40,no.8(April 15, 2006)
• ISSN：1520-5851

文摘

Radioactive strontium (⁹⁰Sr) is an important constituent ofthe complex wastes from past nuclear weapons productionand has been stored in underground tanks at U.S. DOE sites(e.g., Hanford, WA). Using bulk and microfocused EXAFSspectroscopy, we examined temporal changes in solid-phaseSr speciation in kaolinite samples reacted for 1-369 dwith high-pH, high ionic strength synthetic tank-wasteleachate containing Sr²⁺ and Cs⁺ at 10^-3 mol kg^-1. Analysesof bulk EXAFS spectra showed that Sr initially forms aprecipitate by 7 d with a local structure similar to SrCO₃(s). At 33 d, microfocused EXAFS of individual particlesin one sample revealed a mixture of hydrated and dehydratedSr associated with neoformed sodalite-type phases. Ataging times of 93 d and longer, bulk EXAFS spectra andsupporting characterizations indicated nonexchangeable Srwith a local structure consistent with incorporation intoincreasingly crystalline aluminosilicate particles, particularlysodalite. These experimental studies suggest thatirreversible trapping of radionuclides occurs if they arepresent during the formation and aging of feldspathoidalteration products of local Si-bearing sediment minerals.This may serve as an effective contaminant sequestrationmechanism at sites such as Hanford.