DIFFUSION OF CHROMIUM IONS IN POLYMER SILICATE GELS/

Diffusion transport of Cr(III) and Cr(VI) ions in polymer/silicate gel s was studied. The effective diffusion coefficient, break-through time and ion retention capacity were determined as a function of the geome try and the composition of gel. It was found that the effective diffus ion coefficients were very close to the value characteristic in aqueou s solutions and they are proportional to the radii of hydrated ions. T he high retention of Cr(III) ions in gels was attributed to in situ ch emical reactions, mechanical entrapment and sorption. The diffusion ma ss transport of chromium ions could be described by Fick's first law. It was found that the diffusion coefficient decreases, while the break -through time and ion retention increase with the solid content of gel . The relative effect of polymer is greater by an order of magnitude t han that of the silicate content. The influence of gel components can be interpreted by a diffusion model elaborated originally for porous s ystems. It was also shown that the polymer concentration is mostly eff ective in increasing the tortuosity, while in the case of silicate con tent both the porosity and the tortuosity must be considered. The labo ratory experiments provided valuable information and data to design ef ficient profile correction and containment technologies in enhanced oi l recovery and environmental protection. (C) 1998 Elsevier Science B.V . All rights reserved.