Document Detail


Studies of electrochemical properties of compacted clays by concentration potential method.
MedLine Citation:
PMID:  17346739     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The development of concentration (membrane) potential upon step-wise change in salt concentration has been studied for diaphragms made of various strongly compacted clays (montmorillonite, illite, kaolinite) equilibrated with 0.1 M NaCl solution. Porous ceramic filters were used to confine the clays mechanically to be able to achieve high extent of compaction (dry density approximately 2000 kg/m3). A theoretical analysis has revealed that the relaxation pattern is primarily controlled by the properties of porous filters and only slightly depends on the clay properties. At the same time, quasi-stationary values of concentration potential are directly related to the electrochemical perm-selectivity of clay. This property has revealed considerable differences in the electrochemical behaviour of various clays used in this study. This has been attributed to the differences in the micro-structure of clays, in particular to the existence or nonexistence of the so-called interlayer water where cations may retain some mobility. It has also been shown that in clays with high electrochemical perm-selectivity, one can expect a strong increase in the diffusivity of cationic radio-tracers with decreasing ionic strength of equilibrium electrolyte solution. At the same time, low electrochemical perm-selectivity means no noticeable dependence of this kind. The correctness of this observation has been corroborated by the comparison of our findings with the literature data on the diffusion of cationic radio-tracers through compacted montmorillonite (high perm-selectivity) and kaolinite (low perm-selectivity). To check the self-consistency of our approach, we have also carried out sample measurements of diffusion of cationic and anionic radio-tracers through compacted illite. It has been found that the measured effective diffusion coefficients were in excellent agreement with the electrochemical perm-selectivity estimated for this clay from the measurements of concentration potential.
Authors:
Andriy Yaroshchuk; Martin A Glaus; Luc R Van Loon
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Publication Detail:
Type:  Journal Article     Date:  2007-02-16
Journal Detail:
Title:  Journal of colloid and interface science     Volume:  309     ISSN:  0021-9797     ISO Abbreviation:  J Colloid Interface Sci     Publication Date:  2007 May 
Date Detail:
Created Date:  2007-04-16     Completed Date:  2007-07-30     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0043125     Medline TA:  J Colloid Interface Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  262-71     Citation Subset:  IM    
Affiliation:
Laboratory for Waste Management, Paul-Scherrer Institute, 5232 Villigen PSI, Switzerland. andriy.yaroshchuk@upc.edu
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MeSH Terms
Descriptor/Qualifier:
Adsorption
Aluminum Silicates / chemistry*
Electrochemistry
Particle Size
Porosity
Sodium Chloride / chemistry*
Surface Properties
Time Factors
Water / chemistry
Chemical
Reg. No./Substance:
0/Aluminum Silicates; 1302-87-0/clay; 7647-14-5/Sodium Chloride; 7732-18-5/Water

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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