DIFFUSION OF CHROMIUM IONS IN POLYMER SIL ICATE GELS .2. EFFECT OF GEL COMPOSITION ON DIFFUSION PHENOMENA/

The effect of polymer and silicate content on the effective diffusion coefficient, break-through time and specific ion retention was studied . It was found that the diffusion coefficient decreases, while the bre ak-through time and ion retention increases with the solid content of gel. The relative effect of polymer is, however, an order of magnitude greater than that of the silicate content. The influence of gel compo nents can be interpreted by a diffusion model elaborated for porous sy stems. Accordingly, the effect of polymer and silicate might the expla ined through their contribution to modification of the volume fraction of water in the gel and the tortuosity. It was definitely shown that the polymer concentration is mostly effective in increasing the tortuo sity, while in the case of the silicate content both factors must be c onsidered. As far as the practical application of the polymer/silicate gel is concerned it was concluded that the diffusion flux should be c ontrolled primary by the macromolecular component of the searing or bl ocking phase.