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Natural Colloids in Groundwater from a Bentonite Mine- Correlation between Colloid Generation and Groundwater Chemistry -

Published online by Cambridge University Press:  21 March 2011

Yoshio Kuno
Affiliation:
Waste Management and Fuel Cycle Research Center, Japan Nuclear Cycle Development Institute, Tokai Works, Ibaraki, 319-1194, Japan
Gento Kamei
Affiliation:
Waste Management and Fuel Cycle Research Center, Japan Nuclear Cycle Development Institute, Tokai Works, Ibaraki, 319-1194, Japan
Hiroyuki Ohtani
Affiliation:
Research Laboratories, Kunimine Industries Co., Ltd., Tochigi, 325-0013, Japan
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Abstract

Colloids, mainly montmorillonite, generated by erosion of compacted bentonite by groundwater flow might enhance the transport of radionuclides from a radioactive waste repository. The influence of aqueous chemistry (i.e. pH, cation concentration and valence) on the dispersion of montmorillonite colloid was studied. Colloids were flocculated under higher cation concentrations ([Na+] > 10−2 M, [Ca2+] > 10−3 M) and/or under acidic condition (pH = 4) by means of batch-type experiments. Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was applied to estimate the stability of colloidal dispersion and then the limitation of theoretical calculations was pointed out. Groundwater samples were collected from two galleries at different depths of the Tsukinuno bentonite mine (northern Honshu, Japan) and investigated for the populations of colloids. The groundwater flows vertically through Tertiary sedimentary argillaceous rocks and fine tuff beds which are mined for bentonite. Low colloid concentrations were measured in these groundwater samples. This result suggests that the colloids cannot significantly disperse in the groundwaters under higher cation concentration ([Na+] > 10−2 M) or under acidic conditions. This result is consistent with those of the batch-type experiments.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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