Electrochemical permeability measurements of hydrophilic and hydrophobized montmorillonite films: Part I. Characteristics of diffusional transport: Kinetics of break-in/leach-out processes

In the first part of our electrochemical (cyclic voltammetric) study of montmorillonite-modified electrodes, results about film permeability have been presented. The structure of the porous aerogel–hydrogel and the effect of layer-thickness have been discussed. The more compact structure and less permeable Na- and H-montmorillonite result in smaller peak currents characteristic of the permeability of the clay film, than with more permeable Ca-montmorillonite. The thicker the film the less organized the structure and the value of the peak current decreases at increasing thickness.The kinetics of the hydration–dehydration, swelling–shrinking (“break-in/leach-out”) processes and the effect of hydrophobization were demonstrated, too. Kinetical measurement data provide information about diffusional transport via macro, meso-, and micropores, and thus characterize pore structure. Permeability decreases with increasing extents of hydrophobization. The rate constants of structure-dependent macro- and microdiffusion have been calculated.