Formation and Stability of Colloids under Simulated Near Field Conditions

Geckeis, Horst; Grambow, Bernd; Loida, A.; Luckscheiter, B.; Smailos, E.; Quiñones, J.

doi:10.1524/ract.1998.82.special-issue.123

Cited by 28 publications

(19 citation statements)

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“…The observed values indicate that humic colloids in groundwaters of low salinity will be stable for a long time because of repulsive electrostatic forces which are effective among negatively charged colloids. (see, e.g., Feng et al, 1994;Geckeis et al, 1998). Additionally, repulsive forces between colloids and aquifer solids which are likely charged negative, exist (see Ramsey, 1988;Meier et al, 1991).…”

Section: Properties Of Colloids In Gorleben Groundwatersmentioning

confidence: 99%

Modeling of colloid-associated radionuclide transport in porous groundwater aquifers at the Gorleben site, Germany.

Meier

Zimmerhackl²,

Zeitler³

2003

Geochem. J.

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Results are presented which have been obtained in prediction studies on the colloid-associated transport of radionuclides through porous groundwater aquifers overlying as geochemical barrier the planned nuclear repository site at Gorleben, Germany. The studies incorporate three-phase retardation factors for 227 Ac, 228 Th, 232 U and 210 Pb in site-specific groundwater aquifers containing humic colloids and efficiencies for Brownian deposition of colloidal carriers onto immobile sedimentary grains. It is shown that colloidbound radionuclide migration can be approximately modeled by using the basic advection-dispersion transport equation modified with three-phase retardation coefficients and colloid-chemical attachment factors due to the presence of multiple phases, i.e., fluid, colloid and immobile solid. Moreover, results of sitespecific assessment studies indicate that the transport of colloid-associated radionuclides in porous groundwater aquifers overlying the Gorleben salt dome may not occur over long distances, provided that the nuclides are transported by porous flow only. rock salt may reach waste packages so that nuclides might be released (Warnecke et al., 1984(Warnecke et al., , 1994. Therefore, for the performance of a longterm safety assessment the barrier function of the geological formations overlying the salt dome have been studied by batch, column and diffusion experiments (Lieser et al

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Section: Properties Of Colloids In Gorleben Groundwatersmentioning

confidence: 99%

Modeling of colloid-associated radionuclide transport in porous groundwater aquifers at the Gorleben site, Germany.

Meier

Zimmerhackl²,

Zeitler³

2003

Geochem. J.

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“…While the colloidal properties of the radionuclide-bearing phases embedded in the clay colloid matrix will be governed by the clay, information is needed on the chemical and physical properties of the enriched radionuclide-bearing phases which will effect the disassociation/association properties with the clay during transport in a repository environment. Clay colloids have also been observed during the corrosion of other waste glasses under static corrosion tests (Geckeis et al 1998). December 2000…”

Section: Properties Of Colloids Generated From Glass Testsmentioning

confidence: 98%

“…Colloids are known to form by a variety of processes, which include condensation and dispersion (Ahn et al 1993;Geckeis et al 1998;McCarthy and Degueldre 1993). The condensation processes involve nucleation and growth of the colloid from a saturated solution.…”

Section: O-pu-o-mentioning

confidence: 99%

“…156-157) and provide evidence that the TEM results are typical for the bulk solution colloids. During the corrosion of high level waste glass under static test conditions, dissolution of the waste form eventually causes the leachate to reach saturated conditions, which promote nucleation of colloids (Geckeis et al 1998). The silica concentration in the leachates (DTN: LL000123351021.117, pp.…”

Section: Notementioning

confidence: 99%

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Colloid-Associated Radionuclide Concentration Limits: ANL

Mertz¹

2000

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“…According to Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the stability of colloids in aqueous solutions is determined by two interaction energies, van der Waals attraction and interparticle repulsion. The stability of colloid suspensions is ensured by a high repulsive barrier (energy) between particles, which is constrained by pH, ionic strength, as well as time (e.g., [20,[22][23][24]). …”

Section: Introductionmentioning

confidence: 99%

Sodium meta-autunite colloids: Synthesis, characterization, and stability

Zheng

Wan

Song

et al. 2006

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Waste forms of U such as those in the United States Department of Energy's Hanford Site often contain high concentrations of Na and P. Low solubility sodium uranyl phosphates such as sodium meta-autunite have the potential to form mobile colloids that can facilitate transport of this radionuclide. In order to understand the geochemical behavior of uranyl phosphate colloids, we synthesized sodium meta-autunite colloids, and characterized their morphology, chemical composition, structure, dehydration, and surface charge. The stability of these synthetic plate-shaped colloids was tested with respect to time and pH. The highest aggregation rate was observed at pH 3, and the rate decreases as pH increases, indicating that higher stability of colloid dispersion under neutral and alkaline pH conditions. The synthetic colloids are all negatively charged and no isoelectric points were found over a pH range of 3 to 9. The zeta-potentials of the colloids in the phosphate solution show a strong pH-dependence in the more acidic range over time, but are relatively constant in the neutral and alkaline pH range. The geochemical behavior of the synthetic colloids can be interpreted using DLVO theory.The results suggest that formation of mobile sodium meta-autunite colloids can enhance the transport of U in some contaminated sediments.

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Formation and Stability of Colloids under Simulated Near Field Conditions

Cited by 28 publications

References 0 publications

Modeling of colloid-associated radionuclide transport in porous groundwater aquifers at the Gorleben site, Germany.

Modeling of colloid-associated radionuclide transport in porous groundwater aquifers at the Gorleben site, Germany.

Colloid-Associated Radionuclide Concentration Limits: ANL

Sodium meta-autunite colloids: Synthesis, characterization, and stability

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