| 1. |
- Dario, M., et al.
(författare)
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Effects of cement additives on radionuclide mobility
- 2004
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Ingår i: Mater Res Soc Symp Proc. ; , s. 639-644
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Konferensbidrag (refereegranskat)abstract
- The effects of organic cement additives (totally 7) on the sorption of Eu on cement and TiO2 were measured with variation of the concentration of the additive (0.001-10% of the water phase) and reaction time (up to 420 d). There was a significant reduction of the sorption of Eu on cement as well as on TiO2 after 24 h of exposure time in the presence of additives at levels that would be obtained in a cement/water system if the total load of the additive in the cement (up to 3%) would be released into the water phase. Sorption increased with time and would be expected to reach constant levels after 100-200 d. Storage of the additives at 60 and 120°C, pH 12.5, for up to 110 d (in order to degrade them) did not lead to significantly altered sorption behaviour.
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| 2. |
- Dario, Mårten, et al.
(författare)
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Effects of cement additives on radionuclide mobility
- 2004
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Ingår i: Scientific basis for radioactive waste management XXVII. - Warrendale, Pa : Materials Research Society. - 1558997520 ; , s. 639-644
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 3. |
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| 4. |
- Dario, M., et al.
(författare)
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Effects of technical adsorbents and cleaning agents in a cement matrix - A case study
- 2004
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Ingår i: Mater Res Soc Symp Proc. - 1558997520 ; , s. 371-376
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Konferensbidrag (refereegranskat)abstract
- The effects of organic cleaning agents (totally three) and degradation products from solid technical adsorbents (two) on the sorption of Eu on cement and TiO2 were measured with variation of concentration (0.001-10% of the water phase for the cleaning agents, alkaline degradation products corresponding to 0.03-8 mM DOC for the adsorbents) and reaction time (up to 420 d). The effects of the cleaning agents Industrikombi and Prefect Citron were minor. The degradation of the ion exchanger (metaacrylic polymer) had no significant effect on the Eu-sorption. The other adsorbent (filter aid, inert fibre; acrylonitrile polymer) was rapidly degrading at high pH, and the degradation products had a significant reducing effect on the sorption of Eu at added DOC-levels in the mM-range. This category of adsorbent materials should not be incorporated in a cement waste matrix or be stored in a cementitious environment together with radionuclides.
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| 5. |
- Dario, Mårten, et al.
(författare)
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Sorption of europium on TiO2 and cement at high pH in the presence of organic ligands
- 2006
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 270:3, s. 495-505
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Tidskriftsartikel (refereegranskat)abstract
- Organic substances present in radioactive waste lower the sorption of metal ions at the high pH in cement matrices and, hence, enhance their possible migration. The aim of this study was to develop a method to compare organic substances or their degradation products with respect to what extent they affect metal sorption. Batch sorption studies were performed with cement or TiO2 as solid phase and Eu(III) as a model element for trivalent lanthanides and actinides at pH 12.5 (representative of a cement waste matrix during the first approximately 100,000 years). Different kinds of ligands were studied in a broad concentration range, e.g., organic acids, cement additives, cleaning agents and degradation products from ion-exchange resin.
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| 6. |
- Eriksen, Trygve, et al.
(författare)
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Sorption effects on cation diffusion in compacted bentonite
- 1999
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Ingår i: Engineering Geology. - 0013-7952 .- 1872-6917. ; 54:1-2, s. 231-236
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Tidskriftsartikel (refereegranskat)abstract
- Diffusion of Na+. Cs+, Co2+ and Sr2+ in bentonite compacted to a dry density of 1800 kg m(-3) and saturated with groundwaters and aqueous solutions of differing ionic strength have been studied experimentally using the through diffusion technique. Sorption experiments have been carried out under a wide range of pH and concentration of supporting electrolyte. The dependence of the apparent diffusivity of Na+, Cs+ and Sr2+, mainly sorbed by ion exchange, on the sorption intensity is accommodated by a model encompassing diffusion of the sorbed cations within the electrical double layer next to the mineral surface in addition to diffusion in the pore water. The apparent diffusivity of Co2+, sorbed by surface complexation reactions, corresponds to complete immobilization on sorption.
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| 7. |
- Gustafsson, Åsa, et al.
(författare)
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Study of Ni(II) sorption on chlorite - a fracture filling mineral in granites
- 2004
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Ingår i: 28th Symposium on the Scientific Basis for Nuclear Waste Management held at the 2004 MRS Spring Meeting San Francisco, CA, APR 13-16, 2004. ; , s. 373-378
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Konferensbidrag (refereegranskat)abstract
- Chlorite is an Fe(II)-containing phyllosilicate which is often present as a fracture filling mineral in e.g. granitic rocks. It may therefore be significant in influencing redox conditions and sorption processes in granitic groundwaters. The sorption properties of chlorite may therefore be important when modelling the migration of radionuclides under reducing conditions around nuclear waste repositories or in sites contaminated by mining waste. The sorption behaviour of Ni(II) onto a natural chlorite (Karlsborg, Sweden) was investigated using a batch technique. The effects of three different background electrolyte concentrations (0.01 M, 0.1 M and 0.5 M NaClO4) different pH values (ranging from 4 to 11) and different Ni(II) concentrations (10(-6) and 10(-8) M) were studied under anoxic conditions in a glove-box. Ni(II) solutions were spiked with 63 Ni and beta-Liquid scintillation counting (LSC) was used to determine the concentration of nickel in the bulk solution, allowing the calculation of solid-water distribution coefficients for the metal ion. The results of the sorption experiments show strong pH dependence at pH > 5, but the sorption is independent of ionic strength. The maximum adsorption is found in the pH range between 7 and 11 with K-d values approximate to10(3) cm(3)/g. A diffuse double layer model has been used to describe the experimental results.
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| 8. |
- Molera, Mireia, et al.
(författare)
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Anion diffusion pathways in bentonite clay compacted to different dry densities
- 2003
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Ingår i: Applied Clay Science. - 0169-1317 .- 1872-9053. ; 23:1-4, s. 69-76
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Tidskriftsartikel (refereegranskat)abstract
- Diffusion of the anions Cl- and I- in MX-80 compacted bentonite has been studied at different ionic strengths (0.01, 0.1 M NaClO4) and clay density (0.4, 0.8, 1.2, 1.8 g cm(-3)) at the buffered pH of bentonite 8.2 using a through-diffusion technique with measurement of breakthrough curves and concentration profiles in the bentonite. Apparent diffusivities and capacity factors (alpha=epsilon+rhoK(d)) are obtained from diffusion simulations using the computer code ANADIFF. Two diffusion processes, both with density and ionic strength dependent apparent diffusivities and capacity factors, were observed. The diffusion processes observed are ascribed to diffusion in intralayer and interparticle water. The experimental data indicate that intralayer water constitutes the dominating part of water in bentonite compacted to dry the densities 0.4-1.8 g cm(-3) studied in this work.
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| 9. |
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