Spectroscopic characterization of the competitive binding of Eu(III), Ca(II), and Cu(II) to a sedimentary originated humic acid

L. Marang (1, 2) , Sascha Eidner (3) , Michael U. Kumke (3) , Marc F. Benedetti (2) , Pascal E. Reiller (1)

1 LSRM - Laboratoire de Spéciation des Radionucléides et des Molécules
2 EA1880 - Activation et dysfonctionnements des réseaux neuronaux
3 University of Potsdam = Universität Potsdam

The competition between REE, alkaline earth and d-transition metals for organic matter binding sites is still an open field of research; particularly, the mechanisms governing these phenomena need to be characterized in more detail. In this study, we examine spectroscopically the mechanisms of competitive binding of Eu(III)/Cu(II) and Eu(III)/Ca(II) pair to Gorleben humic acid (HA), as previously proposed in the framework of the NICA-Donnan model. The evolution of time-resolved laser induced luminescence spectra of humic-complexed Eu(III) showed two strikingly different environments for a comparable bound proportion for Cu(II) and Ca(II). Cu(II) seems to compete more effectively with Eu(III) inducing its release into the Donnan phase, and into the bulk solution as free Eu3+. This is evidenced both by the shapes of the spectra and by the decrease in the luminescence decay times. In contrast with that, Ca(II) induces a modification of the HA structure, which enhances the luminescence of humic-bound Eu(III), and causes a minor modification of the chemical environment of the complexed rare earth ion.

Domains: Inorganic chemistry; Organic chemistry

L. Marang, Sascha Eidner, Michael U. Kumke, Marc F. Benedetti, Pascal E. Reiller. Spectroscopic characterization of the competitive binding of Eu(III), Ca(II), and Cu(II) to a sedimentary originated humic acid. Chemical Geology, 2009, 264 (1-4), pp.154-161. ⟨10.1016/j.chemgeo.2009.03.003⟩. ⟨cea-00402976⟩