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Sorption of europium on TiO2 and cement at high pH in the presence of organic ligands
Örebro University, Department of Natural Sciences.
Örebro University, Department of Natural Sciences.ORCID iD: 0000-0002-2104-4593
2006 (English)In: Journal of Radioanalytical and Nuclear Chemistry, ISSN 0236-5731, E-ISSN 1588-2780, Vol. 270, no 3, p. 495-505Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2006. Vol. 270, no 3, p. 495-505
National Category
Natural Sciences Chemical Sciences
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:oru:diva-3128DOI: 10.1007/s10967-006-0455-4ISI: 000242148200002Scopus ID: 2-s2.0-33751213363OAI: oai:DiVA.org:oru-3128DiVA, id: diva2:137078
Available from: 2004-04-28 Created: 2004-04-28 Last updated: 2023-12-08Bibliographically approved
In thesis
1. Metal distribution and mobility under alkaline conditions
Open this publication in new window or tab >>Metal distribution and mobility under alkaline conditions
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The adsorption of an element, expressed as its distribution between liquid (aquatic) and solid phases in the biogeosphere, largely determines its mobility and transport properties. This is of fundamental importance in the assessment of the performance of e.g. geologic repositories for hazardous elements like radionuclides. Geologic repositories for low and intermediate level nuclear waste will most likely be based on concrete constructions in a suitable bedrock, leading to a local chemical environment with pH well above 12. At this pH metal adsorption is very high, and thus the mobility is hindered. Organic complexing agents, such as natural humic matter from the ground and in the groundwater, as well as components in the waste (cleaning agents, degradation products from ion exchange resins and cellulose, cement additives etc.) would affect the sorption properties of the various elements in the waste. Trace element migration from a cementitious repository through the pH- and salinity gradient created around the repository would be affected by the presence and creation of particulate matter (colloids) that may serve as carriers that enhance the mobility.

The objective of this thesis was to describe and quantify the sorption of some selected elements representative of spent nuclear fuel (Eu, Am) and other heavy metals (Zn, Cd, Hg) in a clay/cement environment (pH 10-13) and in the pH-gradient outside this environment. The potential of organic complexing agents and colloids to enhance metal migration was also investigated. It was shown that many organic ligands are able to reduce trace metal sorption under these conditions. It was not possible to calculate the effect of well-defined organic ligands on the metal sorption in a cement environment by using stability constants from the literature. A simple method for comparing the effect of different complexing agents on metal sorption is, however, suggested.

The stability in terms of the particle size of suspended colloidal matter (clays and an iron hydroxide) was measured by photon correlation spectroscopy. In the absence of large amounts of organic material, the present colloids will, in most cases, not enhance metal migration in a cementitious environment due to agglomeration of the colloidal phase at high pH and salinities.

Place, publisher, year, edition, pages
Örebro: Örebro universitetsbibliotek, 2004. p. 60
Series
Örebro Studies in Chemistry, ISSN 1651-4270 ; 4
Keywords
Kemi, Adsorption, Colloids, Nuclear waste, Cement, Montmorillonite, miljökemi
National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-66 (URN)91-7668-388-5 (ISBN)
Public defence
2004-05-19, Filmsalen, Forumhuset, Örebro universitet, Örebro, 10:00
Opponent
Supervisors
Available from: 2004-04-28 Created: 2004-04-28 Last updated: 2017-10-18Bibliographically approved

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Dario, MårtenAllard, Bert

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