title: Final storage of radioactive cesium by pollucite hydrothermal synthesis.
abstract: 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.
authors.affiliation: Department of Applied Chemistry, National Defense Academy, Hashirimizu, Yokosuka 239, Japan.
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Yokomori
authors.affiliation: Department of Applied Chemistry, National Defense Academy, Hashirimizu, Yokosuka 239, Japan.
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Asazuki
authors.affiliation: Department of Applied Chemistry, National Defense Academy, Hashirimizu, Yokosuka 239, Japan.
authors.forename: Natsumi
authors.initials: N
authors.lastname: Kamiya
authors.affiliation: Department of Applied Chemistry, National Defense Academy, Hashirimizu, Yokosuka 239, Japan.
authors.forename: Yudai
authors.initials: Y
authors.lastname: Yano
authors.affiliation: Department of Applied Chemistry, National Defense Academy, Hashirimizu, Yokosuka 239, Japan.
authors.forename: Koki
authors.initials: K
authors.lastname: Akamatsu
authors.affiliation: Department of Applied Chemistry, National Defense Academy, Hashirimizu, Yokosuka 239, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Toda
authors.affiliation: Department of Applied Chemistry, National Defense Academy, Hashirimizu, Yokosuka 239, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Aruga
authors.affiliation: Zero Sum Earth Co. Ltd., 6-8-081 Ichiba-cho, Chuo-ku, Chiba 260-0855, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Kaneo
authors.affiliation: Zero Sum Earth Co. Ltd., 6-8-081 Ichiba-cho, Chuo-ku, Chiba 260-0855, Japan.
authors.forename: Seiko
authors.initials: S
authors.lastname: Matsuoka
authors.affiliation: Department of Applied Chemistry, National Defense Academy, Hashirimizu, Yokosuka 239, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Nishi
authors.affiliation: Emeritus Professor, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Matsumoto