Adsorption and desorption of steam on a superabsorbant polyacrylic polymer .4. Effect of mass on kinetics of adsorption and desorption

The effect of steam adsorption-desorption on hydrophilic polymer processes is studied under controlled pressure and temperature. Experiments were performed using a relatively high mass of polymer (2 to 20 g), to examine the influence of different parameters on the adsorption-desorption mechanisms, such as the polymeric adsorbant mass, the steam pressure, the temperature and the number of adsorption-desorption cycles. The limiting step of these processes varies from a pseudo-first-order step type for the low adsorbant mass (< 1 g), to a diffusive step for the mass range 2 to 20 g, In this last range, the process does not depend upon the adsorbant mass; only the adsorption and desorption rates change due to the modification of the space scale of the solid. The adsorption kinetics was not modified by the number of cycles, even for the first cycle; this is the opposite result as compared to when the experiment was performed with a low mass of polymer.