Ion concentration caused by an external solution into the porewater of compacted bentonite

被引:40
作者
Muurinen, A
Karnland, O
Lehikoinen, J
机构
[1] VTT Proc, FIN-02044 Espoo, Finland
[2] Clay Technol AB, Ideon Res Ctr, S-22370 Lund, Sweden
关键词
bentonite; nuclear waste; porosity; exclusion; microstructure; Donnan model;
D O I
10.1016/j.pce.2003.11.004
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
The concentrations caused by the external solution into the porewater were studied with compacted bentonite (MX-80), from which easily dissolving components had been removed in order to ensure that the ions in the porewater came from the external solution. The dry densities of the samples varied from 700 to 1700 kg/m(3) and NaCl solutions of 0.1-3 M were used as the external solution for saturation. The concentrations in the porewater were determined by the direct analysis of the squeezed porewaters and by dispersing the sample in deionized water. At high concentrations, the Donnan model can predict the concentrations in the porewater rather well. At low concentrations, where the ion exclusion is stronger, the measured concentrations are clearly higher than the modelled values. One possible explanation for this discrepancy is the microstructure of the bentonite, and an attempt to couple the effects of the microstructure and the Donnan model was made. It was assumed that there are two pore types, interlamellar pores in the montmorillonite stacks and large pores in the gel between the stacks. The dimensions of the microstructure were obtained from SAXS and BET(N-2) measurements. In this case, the fitting is much better, which supports the assumption of different pore types in bentonite. (C) 2004 Elsevier Ltd. All rights reserved.
引用
收藏
页码:119 / 127
页数:9
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