Formation of Cm humate complexes in aqueous solution at pH(c) 3 to 5.5: The role of fast interchange

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Research Areas

Publication Details

Output type: Other

Author list: Freyer M, Walther C, Stumpf T, Buckau G, Fanghaenel T

Publisher: De Gruyter

Publication year: 2009

Volume number: 97

Issue number: 10

Start page: 547

End page: 558

Number of pages: 12

ISSN: 0033-8230

eISSN: 2193-3405

Languages: English-Great Britain (EN-GB)

Unpaywall Data

Open access status: closed

Abstract

Safety assessment of nuclear waste disposal includes determination of the possible impact of natural dissolved organic matter on the transport of actinide ions via groundwater into the biosphere. Thereby, much attention is paid to americium as it dominates the radiotoxicity of the nuclear waste after about 300 y and up to about 1000 y (spent fuel) or 100 000 y (vitrified reprocessing waste). A trustworthy description of the influence benefits from a sound chemical process understanding of the americium humate complexation and transport processes. A problem in this respect is that studies by TRLFS lead to inconclusive results with respect to the nature of the complexes involved. In the present study the outcome of TRLFS measurements in H2O and D2O, and at room temperature and in liquid nitrogen are compared. It is shown that the Cm3+ ion interchanges between aquo ion (Cm-aq(3+)) and humate complex (CmHA) on a time scale of milliseconds in a pH range between 3 and 5.5. Taking this interchange into account, the process can be described in the absence of ternary complexes by the 1 : 1 stoichiometry formation of one curium humate complex, or a sufficiently narrow distribution of complexes to be represented by one average complex.

Keywords

Curium, Humic substances, Time resolved laser fluorescence, TRLFS

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