Chabazite: Stable Cation-Exchanger in Hyper Alkaline Concrete Pore Water

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• 作者：Leen Van Tendeloo ; Wauter Wangermez ; Mert Kurttepeli ; Benny de Blochouse ; Sara Bals ; Gustaaf Van Tendeloo ; Johan A. Martens ; Andr茅 Maes ; Christine E. A. Kirschhock ; Eric Breynaert
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：February 17, 2015
• 年：2015
• 卷：49
• 期：4
• 页码：2358-2365
• 全文大小：408K
• ISSN：1520-5851

文摘

To avoid impact on the environment, facilities for permanent disposal of hazardous waste adopt multibarrier design schemes. As the primary barrier very often consists of cement-based materials, two distinct aspects are essential for the selection of suitable complementary barriers: (1) selective sorption of the contaminants in the repository and (2) long-term chemical stability in hyperalkaline concrete-derived media. A multidisciplinary approach combining experimental strategies from environmental chemistry and materials science is therefore essential to provide a reliable assessment of potential candidate materials. Chabazite is typically synthesized in 1 M KOH solutions but also crystallizes in simulated young cement pore water, a pH 13 aqueous solution mainly containing K⁺ and Na⁺ cations. Its formation and stability in this medium was evaluated as a function of temperature (60 and 85 掳C) over a timeframe of more than 2 years and was also asessed from a mechanistic point of view. Chabazite demonstrates excellent cation-exchange properties in simulated young cement pore water. Comparison of its Cs⁺ cation exchange properties at pH 8 and pH 13 unexpectedly demonstrated an increase of the K_D with increasing pH. The combined results identify chabazite as a valid candidate for inclusion in engineered barriers for concrete-based waste disposal.