Abstract
Self-diffusion coefficients were determined for organic adsorbates (2-propanol and acetone) in triamine-modified and unmodified controlled-pore glasses, using the pulsed field gradient NMR technique. Saturated amounts of adsorption were decreased considerably by the surface modification, indicating the reduction of free space for adsorption. With modified surface, both diffusivity and permeability were increased irrespective of the state of adsorption (unmixed or mixed). With unmodified surface, the order of diffusivity was reversed for 2-propanol and acetone by changing the state of adsorption ; the same reversal was also observed for permeability. This common characteristic feature is interpreted in terms of preferential adsorption of acetone (vs. 2-propanol) on hydroxyl (acidic) adsorption sites on the glass surface. Modification of surface acidity by treating with aqueous aluminium nitrate (or sodium acetate) supports this view.
Together with the common trend in diffusivity and permeability for the triamine-modified surface, importance of diffusivity in determining the permeation property is suggested.
