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Aqueous chemistry of Ce(IV): estimations using actinide analogues

Abstract

Prediction of Cerium (Ce) aqueous speciation is relevant in many research fields. Indeed, Ce compounds are used for many industrial applications, which may require the control of Ce aqueous chemistry for their synthesis. Aquatic geochemistry of Ce is also of interest. Due to growing industrial use and its release to the environment, Ce is now considered as emerging contaminant. Cerium is also used as a proxy of (paleo)redox conditions due to the Ce(IV)/Ce(III) redox transition. Finally, Ce(IV) is often presented as a relevant analogue of tetravalent actinides (An(IV)). In the present study, quantum chemical calculations were conducted to highlight similarities between the structure of Ce(IV) and tetravalent actinides (An(IV); An = Th, Pa, U, Np, Pu) aqua-ions, especially Pu(IV). Current knowledge of An(IV) hydrolysis, solubility and colloid formation in water were briefly reviewed but important discrepancies observed with available data for Ce(IV). Therefore, new estimation of the hydrolysis constants of Ce(IV) and solubility of Ce(IV)-(hydr)oxides are proposed, by analogy with Pu(IV). By plotting pH-Eh (Pourbaix) diagrams, we showed that the pH values corresponding to the onset of Ce(IV) species formation (i.e. Ce(IV)-(hydr)oxide or dissolved Ce(IV)) agreed with various experimental results. Although, further experimental studies are required to obtain a more accurate thermodynamic database, the present work might yet help to predict more accurately Ce chemical behavior in aqueous solution.

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Publication details

The article was received on 21 Jun 2017, accepted on 13 Sep 2017 and first published on 13 Sep 2017


Article type: Paper
DOI: 10.1039/C7DT02251D
Citation: Dalton Trans., 2017, Accepted Manuscript
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    Aqueous chemistry of Ce(IV): estimations using actinide analogues

    R. Marsac, F. Réal, N. L. Banik, M. Pedrot, O. Pourret and V. Vallet, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT02251D

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