| 1. |
- García García, Sandra, et al.
(author)
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Effects of temperature on the stability of colloidal montmorillonite particles at different pH and ionic strength
- 2009
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In: Applied Clay Science. - : Elsevier BV. - 0169-1317 .- 1872-9053. ; 43:1, s. 21-26
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Journal article (peer-reviewed)abstract
- The effect of temperature at different pH and ionic strengths on the aggregation kinetics of colloidal montmorillonite particles in aqueous dispersions was investigated. For a given temperature and pH, the rate constant for aggregation increased with increasing ionic strength. At pH:54 the rate constant for colloid aggregation increased with increasing temperature, regardless of ionic strength. At pH 10 the aggregation rate constant decreased with increasing temperature as a general trend. In the intermediate pH interval, the aggregation rate constant apparently decreased with increasing temperature except at the highest ionic strength, where it increased with increasing temperature. The aggregation rate constant decreased at alkaline pH compared with the acidic pH range. This effect became more pronounced at higher ionic strengths and higher temperatures but could not be observed at 4 degrees C. These observations are in qualitative agreement with DLVO calculations taking temperature, pH and ionic strength into account.
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| 2. |
- Holmboe, Michael, et al.
(author)
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Effects of gamma-irradiation on the stability of colloidal Na+-Montmorillonite dispersions
- 2009
-
In: Applied Clay Science. - : Elsevier BV. - 0169-1317 .- 1872-9053. ; 43:1, s. 86-90
-
Journal article (peer-reviewed)abstract
- In many concepts for final storage of spent nuclear fuel bentonite will be used as an engineered barrier, mainly due to its inertness, plasticity and ability to retard transport of radionuclides by adsorption. In the event of water-bearing fractures making contact with the bentonite barrier, generation and transport of colloidal particles will strongly depend on groundwater composition and the surface properties of the colloidal particles. The bentonite barrier will unavoidably be exposed to ionizing radiation from the spent nuclear fuel but very little is known about effects of ionizing radiation on bentonite concerning colloidal stability. In this work we have studied the effect of gamma-radiation on the stability of dilute colloidal Na+-montmorillonite dispersions using a Cs-137 gamma-source (doses of 0-53.2 kGy). Aggregation kinetics and sedimentation experiments revealed significant radiation effects, evident as increased colloid stability. The only rationale for this is a gamma-radiation induced increase in surface potential. The effects appeared to depend on the Na+-montmorillonite concentration in the irradiated dispersions, indicating that the change in surface potential is induced by aqueous radiolysis products.
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| 3. |
- Holmboe, Michael, et al.
(author)
-
Effects ofγ-irradiation on the stability of colloidal Na+-Montmorillonite dispersions
- 2008
-
In: Applied Clay Science. - : Elsevier. - 0169-1317 .- 1872-9053. ; 43, s. 86-90
-
Journal article (peer-reviewed)abstract
- In many concepts forfinal storage of spent nuclear fuel bentonite will be used as an engineered barrier,mainly due to its inertness, plasticity and ability to retard transport of radionuclides by adsorption. In theevent of water-bearing fractures making contact with the bentonite barrier, generation and transport ofcolloidal particles will strongly depend on groundwater composition and the surface properties of thecolloidal particles. The bentonite barrier will unavoidably be exposed to ionizing radiation from the spentnuclear fuel but very little is known about effects of ionizing radiation on bentonite concerning colloidalstability. In this work we have studied the effect ofγ-radiation on the stability of dilute colloidal Na+-montmorillonite dispersions using a Cs-137γ-source (doses of 0–53.2 kGy).Aggregation kinetics and sedimentation experiments revealed significant radiation effects, evident asincreased colloid stability. The only rationale for this is aγ-radiation induced increase in surface potential.The effects appeared to depend on the Na+-montmorillonite concentration in the irradiated dispersions,indicating that the change in surface potential is induced by aqueous radiolysis products.
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| 4. |
- Larsson, Stefan, et al.
(author)
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A laboratory study on strength loss in kaolin surrounding lime-cement columns
- 2009
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In: Applied Clay Science. - : Elsevier BV. - 0169-1317 .- 1872-9053. ; 44:1-2, s. 116-126
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Journal article (peer-reviewed)abstract
- This study evaluated property changes in laboratory-prepared kaolin surrounding lime-cement columns. The parameters investigated included geotechnical parameters such as undisturbed undrained shear strength, remoulded shear strength, water content, and Atterberg limits. In addition the exchangeable Ca2+, Na+ and K+ ion concentrations were assessed. Four types of small-scale lime-cement columns were manufactured using different production methods and binder blending ratios. Tests were performed 7, 14, 30 and 90 days after installation. The migration of Ca2+, Na+ and V ions from the lime-cement columns into the surrounding soil has been confirmed through the chemical analysis on a large number of samples taken. The results illustrate that the undrained shear strength properties in the surrounding kaolin were significantly affected by the migration of Ca2+, Na+ and K+ ions. An increase in the Na+ and K+ ion concentrations in the front of the migrated Ca2+ ions was observed. The tests illustrate that, under the experimental conditions chosen, the remoulded undrained shear strength decreased in a thin zone as a result of the migrated Na+ and K+ ions. The magnitude of the strength loss depended on the binder blending ratio in the lime-cement columns.
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