The kinetic mechanism of water adsorption/desorption on samples of natural clinoptilolite-K has been investigated by using an electrical method based on measurements of variation of AC current intensity during the time. In particular, a high-frequency sinusoidal voltage (5kHz) was applied to the sample (high frequency was required to avoid sample/electrode interface polarization phenomena) and the resulting AC micro-current intensity was monitored during the time. The sample was hydrated by exposition to a 75% humidity atmosphere, while dehydration was achieved by exposing the sample to activated silica gel in a close container or simply taking it in air. The hydration reaction followed a pseudo-zero-order kinetics, while the dehydration reaction followed a first-order kinetics both in air or dry atmosphere. The observed kinetic behaviors can be explained on the basis of a 'catalytic effect' of cations in both water adsorption and desorption from the 3D-framework walls.
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