Swelling and dehydration characteristics of transition metal ion-exchanged taeniolites

The swelling and dehydration characteristics of Mn²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ ion-substituted taeniolites with the exchange ratios of 85% and 78% have been investigated by high-temperature X-ray diffractometry, thermogravimetry-differential thermal analysis and calorimetry. The transition metal forms are the swelling states with two water-molecule layers at room temperature and a relative humidity of 70%, and their dehydration processes to the swelling states with a half water-molecule layer were concluded from the experimental results, to depend on the kind of the interlayer cations. In particular, the new swelling state with three-quarters water-molecule layers, showing a rational series of the basal reflections, was discovered to exist stably in the dehydration processes of manganese and nickel forms. The heat of swelling with water attains a maximum at a temperature corresponding to the appearance of the swelling state with a half water-molecule layer. The calorific value for the copper form was measured to be much larger than those for manganese, nickel and zinc forms.