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首页> 外文期刊>Environmental Science & Technology >Mechanical Compaction of Smectite Clays Increases Ion Exchange Selectivity for Cesium
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Mechanical Compaction of Smectite Clays Increases Ion Exchange Selectivity for Cesium

机译：绿土粘土的机械压实提高了铯的离子交换选择性

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摘要

A key discussion in radioactive waste disposal is the question of whether adsorption behavior of radionuclides in dispersed and in highly compacted materials is similar. It is common practice to measure sorption data on dispersed systems and to use these data to predict the sorption in compacted systems. The latter represent the situation in a real, deep geological repository system. The discussions focus mainly on items such as the effect of compaction on the accessibility of sorption sites, that is, on sterical effects, and not on the effect of compaction on the thermodynamics of the sorption processes. Here we show that in the case of sorption of cesium on sodium bentonite, material compaction indeed affects the thermodynamics of the sorption process such that sorption increases. This increase is due to a reduction of the interlayer space, leading to a lower ability of the interlayer water for cation hydration. Cations with a low hydration tendency, such as cesium, therefore accumulate in the interlayer space, whereas highly hydrated cations such as sodium tends to accumulate in the bulk water where water is easily available for hydration. The fact that mechanical compaction affects the thermodynamics of ion exchange processes in clay is an important finding and brings in a new aspect in the discussion on the transferability of thermodynamic data from diluted to compacted systems. The common practice of applying chemical and thermodynamic concepts valid for diluted systems to compacted systems must be basically scrutinized.
机译：放射性废物处理中的一个关键讨论是，放射性核素在分散的和高度压实的材料中的吸附行为是否相似。通常的做法是测量分散系统上的吸附数据，并使用这些数据预测压实系统中的吸附。后者代表了真实的深层地质处置库系统中的情况。讨论主要集中在诸如压实对吸附位点可及性的影响，即空间效应，而不是压实对吸附过程的热力学的影响。在这里，我们表明在铯在膨润土钠上的吸附情况下，材料的压实确实会影响吸附过程的热力学，从而增加吸附。该增加归因于中间层空间的减小，导致中间层水阳离子水合的能力降低。因此，水合趋势低的阳离子（例如铯）会在层间空间中积聚，而水合度高的阳离子（例如钠）会在大量水中积聚，而水很容易被水化。机械压实会影响粘土中离子交换过程的热力学这一事实是一个重要发现，并为热力学数据从稀释系统到压实系统的可传递性的讨论带来了新的方面。必须仔细研究将对稀释系统有效的化学和热力学概念应用于紧凑系统的普遍做法。

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  • 来源
    《Environmental Science & Technology》 |2008年第5期|1600-1604|共页
  • 作者

    LUC R. VAN LOON; MARTIN A. GLAUS;

  • 作者单位
  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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