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Observations on Activity and Diffusion Coefficients in Na‐Montmorillonite
Author(s) -
Low P. F.
Publication year - 1968
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.196800042
Subject(s) - viscosity , diffusion , chemistry , ionic bonding , thermodynamics , ion , ionic strength , diffusion layer , materials science , physics , layer (electronics) , aqueous solution , organic chemistry
Abstract Double‐layer theory was used to obtain the distribution of electrical potential between adjacent clay particles. From this distribution, the activity coefficients of the sodium and chloride ions in the system were calculated. The calculated values were close to the observed ones. The porosity of the clay‐water system was calculated from the density and concentration of clay. The calculated value was used to calculate the geometry factor. Then this factor and the diffusion coefficient of water in bulk water were used to calculate the diffusion that water would have in the clay if the water therein had its normal viscosity. Results indicated that the water in the clay was about twice as viscous as normal water. Having the geometry factor and the viscosity of the water in the system, it was possible to compute the diffusion coefficients that Na + and Cl − would have in the absence of electrical interaction with the clay. The computed values were close to those observed. To obtain closer agreement, electrical field strengths calculated by double‐layer theory were used in an empirical equation relating viscosity and field strength to obtain the distribution of viscosity relative to the particle surfaces. Also, double‐layer theory was used to obtain ionic distributions with respect to these surfaces. From the resulting distributions it was possible to determine, by means of appropriate equations, the ionic diffusion coefficients that should obtain in the clay system. Diffusion coefficients determined in this manner were somewhat better than those calculated without regard for electrical effects.