An equation for estimating the diffusion coefficient of electrolytes in ion exchange membranes

✍ Scribed by Hirofumi Miyoshi; Tsugio Fukumoto; Takeshi Kataoka

• Publisher: Elsevier Science
• Year: 1983
• Tongue: English
• Weight: 627 KB
• Volume: 48
• Category: Article
• ISSN: 0011-9164
• DOI: 10.1016/0011-9164(83)80004-6

✦ Synopsis

When operating electrodialysis equipment with ion exchange membranes, the diffusion coefficient in the membrane must be predetermined. We derived an equation to estimate the diffusion coefficient with only one unknown factor by assuming that the mobility of counter-ions in the membrane was proportional to that in the solution.

The diffusion experiments were studied by a stirring cell method. The value of an apparent permeability coefficient became constant after 7200 seconds. The value was approximately equal to that of the permeability coefficient in the membrane at 200 rpm. The diffusion coefficients in the membranes were obtained for various electrolytes. The unknown factor was determined by comparing the theoretical with the experimental value of the diffusion coefficient, and a final equation to estimate the diffusion coefficient was derived. The diffusion coefficient in the membrane increased slightly with the increase of the electrolyte concentration. SYMBOLS C -concentration, mol cmm3 D -diffusion coefficient, cm* s-i d diameter of impeller, cm e -void fraction, -F -Faraday constant, C g-eq-' J -ion flux, mol cm-* s-* K -permeability coefficient, cm s-' 1 -equivalent ionic conductance, cm* a-' g-eq-' mfactor of (Y, -