Mechanochemical reactions of clay minerals with CsCl

Abstract

Solid state mechanochemical reactions between clay minerals and CsCl during grinding in non-destructive techniques, investigated in our laboratory, are reviewed. Clays were talc, pyrophyllite, sepiolite, palygorskite and minerals from the serpentine-kaolin and smectite groups. No reaction occurred with serpentines, talc, pyrophyllite and palygorskite. Cation-exchange occurred with montmorillonite and saponite. Kaolin-type minerals were delaminated forming disordered aggregates of TO layers with water, Cs cations and Cl anions. XRD did not show any peak but IR spectra proved the presence of H-bonds between water molecules, and inner-surface oxygens or inner-surface hydroxyls. After water thermal evolution CsCl intercalation complexes with a spacing of 1050 pm were identified. Wet-grinding of sepiolite with CsCl resulted in the disappearance of sepiolite XRD peaks indicating a disintegration of the crystal into micro-crystallites with no order in their packing in the particle. Air-grinding of sepiolite with CsCl almost did not change the X-ray pattern of sepiolite.