Calcination of manganese carbonate-potassium-tert-butoxide mixture at 500°C and hydrothermal treatment of mixed manganese sulfate-ammonium sulfate-ammonium peroxodisulfate solution yielded cryptomelane and NH₄-cryptomelane, respectively. The structural K and NH₄ could be partially replaced with H by washing with HNO₃, where column washing with 6 mol/L HNO₃ was much more effective than batch washing with diluter HNO₃. The H-exchanged cryptomelane greatly preferred K over Ca and Mg. The presence of 0.05 mol/L of Ca and Mg did not affect the K adsorption at all. The contact of wetted soil with H-exchanged cryptomelane across membrane filter caused diffusive migration of K from the soil to cryptomelane. The amount of K transferred to the cryptomelane in 96 h was almost double the amount of exchangeable K in soil, suggesting that this will be a new method for accessing K-supplying power of soils.

A vermiculite clay mineral was applied as a column material of high performance liquid chromatography (HPLC) in order to eliminate radioactive Cs⁺ ions from contaminated water. A column was prepared by packing 2 g of vermiculite into a stainless tube of 0.6 cm (i.d.) × 5 cm (length). When an aqueous solution containing 0.1 mM of CsNO₃ and 1M of Mg(NO₃)₂ was passed through the tube, Cs⁺ ions were captured effectively until the flowed volume attained ca. 30 mL. Based on the results, it was estimated that the same column was capable of purifying 4.8 liter of water contaminated at the radioactive level of 3000 Bq/kg.

The adsorption of water molecules on the surface of a clay mineral was studied by means of quartz crystal microbalance (QCM) measurements. For the purpose, an ultra-thin film of exfoliated montmorillonite sheets was prepared by the modified Langmuir method. On introducing a nitrogen gas at various humidity, the adsorption and desorption processes of water molecules on a clay film were monitored in terms of mass change. The adsorbed amount of water molecules was compared among the following four films: (F1) a single-layered clay-amphiphile hybrid film, (F2) a single layered clay film, (F3) a double layered clay-amphiphile hybrid film and (F4) a double-layered clay film. The nature of adsorbed water molecules was investigated by comparing the IR spectra between F1 and a cast film.