Emanation thermal analysis (ETA), thermogravimetry and high temperature XRD were used to characterize the thermal behavior
during dehydration of natural Na montmorillonite (Upton Wyoming, USA) and homoionic montmorillonite (MMT) samples saturated
with different cations, i.e. Li+, Cs+, NH4+, Mg2+ and Al3+. ETA results characterized radon mobility and microstructure changes that accompanied the mass loss of the samples due to
dehydration on heating in air. A collapse of interlayer space between the silicate sheets after water release from the MMT
samples was characterized by a decrease of the radon release rate, ΔE. Decreases in c-axis basal spacing (d001) values determined from XRD patterns for the different montmorillonite samples follow the sequence:
The decrease of the radon release rate (ΔE) determined by ETA that characterized microstructure changes due to collapse of interlayer space corresponded well to differences
in the c-axis basal spacing (Δd001) values determined from the XRD patterns before and after samples dehydration.