Department of Applied Chemistry, National Defense Academy, Hashirimizu, Yokosuka 239, Japan.
Zero Sum Earth Co. Ltd., 6-8-081 Ichiba-cho, Chuo-ku, Chiba 260-0855, Japan.
Sci Rep. 2014 Feb 26;4:4195. doi: 10.1038/srep04195.
The Fukushima nuclear accident has highlighted the importance of finding a better final storage method for radioactive cesium species. Cs is highly soluble in water, and can easily exchange with other alkali ions in zeolites or clays to form stable complexes. However, Cs(+) is released from Cs(+) complexes into water when surrounded by an excess of water. Pollucite may be the best final storage option for Cs(+), but its typical synthesis requires heating to about 1200 °C in air. Here, we show that the hydrothermal synthesis of pollucite can be completed at 300 °C in three hours from any zeolite or clay. Furthermore, our procedure does not require ion exchange before synthesis. Radioactive Cs is usually found in complexes with clays. At that time, this method only requires calcium hydroxide, water, and three hours of hydrothermal synthesis, so the process is both inexpensive and practical for large-scale application. Pollucite is an analog of analcime zeolite, and contains a channel system 2.8 Å in diameter, which is formed by 6-oxygen rings. As the diameter of Cs(+) is 3.34 Å and each Cs(+) exists independently within a separate portion of the channel, Cs(+) cannot exit the pollucite framework without breaking it.
福岛核事故凸显了寻找更好的放射性铯物种最终存储方法的重要性。Cs 在水中高度溶解，并可在沸石或粘土中与其他碱金属离子轻易交换，形成稳定的配合物。然而，当周围有过量的水时，Cs(+)会从 Cs(+)配合物中释放到水中。方沸石可能是 Cs(+)的最佳最终存储选择，但它的典型合成需要在空气中加热至约 1200°C。在这里，我们表明，方沸石的水热合成可以在 300°C 下在三小时内完成，无论沸石或粘土如何。此外，我们的方法在合成前不需要离子交换。放射性 Cs 通常与粘土形成配合物。在那时，这种方法只需要氢氧化钙、水和三小时的水热合成，因此该过程既经济又适用于大规模应用。方沸石是方沸石沸石的类似物，含有一个直径为 2.8 Å 的通道系统，由 6-氧环形成。由于 Cs(+)的直径为 3.34 Å，并且每个 Cs(+)独立存在于通道的不同部分，因此 Cs(+)在不破坏它的情况下无法离开方沸石骨架。
