Alteration of montmorillonite by KOH solutions

Ueda, Mai*; Nakabayashi, Ryo*; Kijima, Tatsuya*; Sato, Tsutomu*; Yoneda, Tetsuro*; Otake, Tsubasa*; Oda, Chie  

In the current study, the promoted illitization of montmorillonite in KOH solutions was investigated. Montmorillonite was added to 0, 0.1, 0.5, 1.0, and 3.0 M KOH solutions, which were then sealed and kept at 35 or 60 C for up to 270 days. Reaction products were analyzed by XRD to check the expandability, an empirical determination of layer charge and observation by AFM. 10 and 35% of illite layer in randomly interstratified illite/smectite minerals were estimated by XRD for 0.1 M and 3.0 M solutions, respectively. Changes in the peak intensities obtained from the XRD patterns could be assigned to the dissolution of montmorillonite, but with some uncertainty affected the reliability of the quantification of illite. No significant illitization was observed based on the results of layer charge and AFM observation. Consequently, there is no direct evidence for significant illitization of montmorillonite in KOH solutions under the experimental conditions of the current study.