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Title: Complexation parameters for the actinides(IV)-humic acid system : a search for consistency and application to laboratory and field observations
Authors: Reiller, Pascal E.
Evans, Nick
Szabo, Gyula
Keywords: Actinides
Humic substances
Complexation
Thorium
Plutonium
Uranium
Analogy
Redox
Issue Date: 2008
Publisher: © Oldenbourg Wissenschaftsverlag, München
Citation: REILLER, P.E., EVANS, N. and SZABO, G., 2008. Complexation parameters for the actinides(IV)-humic acid system : a search for consistency and application to laboratory and field observations. Radiochimica Acta, 96 (6), pp.345-358
Abstract: The coherence of actinide(IV) complexation by humic substances (HS) is reviewed and new data are proposed. In a first attempt, the values of independent data from literature on Th(IV), U(IV), and Pu(IV) are collected, selected, and compiled. The data obtained follow the “classical” trend of increasing conditional formation “constant” with pH, led both by the increasing ionisation of HS and by the extensive hydrolysis of the tetravalent actinides. Even though a fair agreement is evident, the experimental uncertainties do not permit a full analogy between the actinides(IV) to be ascertained. In a second attempt, the experiments from which the original data are available were reinterpreted using only one hydrolysis constant set for U(IV) as an exemple, considering that all actinides(IV) have analoguous humic complexation behaviour. Hence, the obtained evolution of conditional formation “constant” is much more coherent and the uncertainties do not permit to distinguish an actinide(IV) from one another. The obtained data are then applied to independent laboratory and in situ experiments in order to delimit the domain of possible applicability. This exercise demonstrates the treatment of data through analogy in the case of actinides(IV) and would permit to limit and orientate the number of necessary, but difficult, experiment with redox sensitive elements like U, Np, or Pu. It also demonstrate that complexation-only mechanisms may not be sufficient to understand field observations.
Description: This article is Restricted Access. It was published in the journal, Radiochimica Acta [© Oldenbourg Wissenschaftsverlag, München] and is available at: http://www.atypon-link.com/OLD/loi/ract
Version: Restricted access
DOI: 10.1524/ract.2008.1500
URI: https://dspace.lboro.ac.uk/2134/4045
ISSN: 0033-8230
Appears in Collections:Closed Access (Chemistry)

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