The complexation of Cm(III) and Eu(III) with dissolved silica was studied by time resolved laser fluorescence spectroscopy (TRLFS) in basic solutions over a range of total silica concentrations and ionic strengths (NaNO3). In highly basic solutions, both the fluorescence spectra and lifetime data indicate the formation of Eu(III)/Cm(III) complexes with oligomeric silicates as well as hydroxide groups and/or nitrate in the presence of concentrated NaNO3. At high silica concentration the inner-sphere complexation caused the shift of the fluorescence spectral maximum for Cm(III)(aq) from 594 nm to up to 607 nm and a significant increase of the hypersensitive 5D0 ? 7F2 band around 615 nm relative to the non-hypersensitive 5D0 ? 7F1 band at 592 nm for Eu(III). At the same time, the fluorescence lifetime increased from 68 ?s to up to 202 ?s for Cm(III) in 0.1 M NaNO3 and from 115 ?s to 1.8 ms for Eu(III) in 3.0 M and 5.0 M NaNO3, consistent with the removal of 6 or more water molecules upon silicate complexation. Linear correlations between the spectral intensity of Cm(III) complexes and the concentrations of the dissolved silicates suggest that Cm(III) complexation with the silicate dimer, Si2O2(OH)22-, may play a role.
Revised: May 18, 2011 |
Published: December 1, 2005
Citation
Wang Z., A.R. Felmy, Y. Xia, O. Qafoku, W. Yantasee, and H.M. Cho. 2005.Complexation of Cm(III)/Eu(III) with Silicate in Basic Solutions.Radiochimica Acta 93, no. 12:741-748.PNNL-SA-42709.