title: Uptake of Cm(III) and Eu(III) by calcium silicate hydrates: a solution chemistry and time-resolved laser fluorescence spectroscopy study.
abstract: The interaction of the two chemical homologues [Cm(III) and Eu(III)] with calcium silicate hydrates (CSH phases) at pH 13.3 has been investigated in batch-type sorption studies using Eu(III) and complemented with time-resolved laser fluorescence spectroscopy (TRLFS) using Cm(III). The sorption data for Eu(III) reveal fast sorption kinetics and a strong uptake by CSH phases with distribution ratios of (6 +/- 3) x 10(5) L kg(-1). Three different Cm(III) species have been identified: A nonfluorescing species, which was identified as a curium hydroxide (surface) precipitate, and two fluorescing Cm(III)/CSH-sorbed species. The fluorescing sorbed species have characteristic emission spectra with main peak maxima at 618.9 and 620.9 nm and fluorescence emission lifetimes of 289 +/- 11 and 1482 +/- 200 micros, respectively. From the fluorescence lifetimes, it was calculated that the two fluorescing Cm(III) species have one or two and no water molecules left in their first coordination sphere, suggesting that these species are incorporated into the CSH structure. A structural model for Cm(III) and Eu(III) incorporation into CSH phases is proposed based on the substitution for Ca at two different types of sites in the CSH structure.
authors.affiliation: Paul Scherrer Institute, Waste Management Laboratory, CH-5232 Villigen-PSI, Switzerland.
authors.forename: Jan
authors.initials: J
authors.lastname: Tits
authors.forename: Thorsten
authors.initials: T
authors.lastname: Stumpf
authors.forename: Thomas
authors.initials: T
authors.lastname: Rabung
authors.forename: Erich
authors.initials: E
authors.lastname: Wieland
authors.forename: Thomas
authors.initials: T
authors.lastname: Fanghänel
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry*; D003252:Construction Materials; D003476:Curium / Q000032:analysis / Q000737:chemistry*; D005063:Europium / Q000032:analysis / Q000737:chemistry*; D007700:Kinetics; D007834:Lasers; D008962:Models, Theoretical; D011850:Radioactive Waste; D017640:Silicates / Q000737:chemistry*; D012995:Solubility; D013050:Spectrometry, Fluorescence
chemical_list: D017610:Calcium Compounds; D011850:Radioactive Waste; D017640:Silicates; D005063:Europium; D003476:Curium; C031293:calcium silicate