Ion Diffusion: II. Comparison of Apparent Self and Counter Diffusion Coefficients

Abstract

Listen

Translate article

AbstractThe experimental distributions of Rb86 diffusing in soil materials are obtained using a quick‐freeze method. The calculation of apparent diffusion coefficients of Rb from data obtained from these distributions is presented for the following geometries: (1) self diffusion and (2) counter diffusion of Rb diffusing from soil media initially saturated with Rb into the same soil media initially saturated with H+. The distribution of Rb86 counter diffusing from kaolinite clay, montmorillonite clay, Sharkey clay soil and Dundee silt loam soil pastes into H+ saturated kaolinite, montmorillonite, Sharkey and Dundee pastes can be characterized using self diffusion theory.The order of magnitude of apparent self diffusion coefficients is larger than those for counter diffusion in each of the four soil materials. The order of magnitude of the rate of Rb diffusion in the four soil materials is as follows: kaolinite clay > Dundee silt loam soil > Sharkey clay > montmorillonite clay. The values of the diffusion coefficients range from 3.9 × 10−7 cm.2 sec.−1 to 24.3 × 10−7 cm.2 sec.−1.Qualitative apparent counter diffusion coefficients of Rb diffusing from soil media initially saturated with Rb into strong acid exchange‐resin discs initially saturated with H+ are also presented for qualitative comparison purposes.