Stepwise Hydration of High-Quality Synthetic Smectite with Various Cations

Kenji Tamura1, Hirohisa Yamada2 and Hiromoto Nakazawa2
1 Central Research Laboratory, Kawasaki, Showa Denko K.K., 3-2 Chidori-cho, Kawasaki-ku, Kawasaki, Kanagawa, 210-0865 Japan
2 National Institute for Research in Inorganic Materials, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044 Japan
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Abstract: Smectites synthesized from experiments at 5.5 GPa and 1500°C are of high quality, crystals are large at >10 µm, and the 2:1 layers may have a homogeneous charge distribution. Smectite was exchanged with various cations (Na+, Li+, K+, Ca2+, and Mg2+) and the hydration behavior of each sample was observed by an in situ powder X-ray diffraction method under precisely controlled relative humidity (RH). The smectite showed distinct stepwise (discontinuous) hydration versus RH. During the transition between two hydration states, the coexistence of the two states was observed. Randomly interstratified structures with one and two planes of H2O are time-dependent phenomena and relate to hydration and dehydration processes.

Key Words: Crystalline Swelling • Hydration • Interlayer Cation • Smectite

Clays and Clay Minerals; June 2000 v. 48; no. 3; p. 400-404; DOI: 10.1346/CCMN.2000.0480311
© 2000, The Clay Minerals Society
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