Time-Resolved Laser Fluorescence Spectroscopy Study of the Sorption of Cm(III) onto Smectite and Kaolinite
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- 作者：Thorsten Stumpf ; Andreas Bauer ; Frederic Coppin ; and Jae Il Kim
- 刊名：Environmental Science & Technology
- 出版年：2001
- 出版时间：September 15, 2001
- 年：2001
- 卷：35
- 期：18
- 页码：3691 - 3694
- 全文大小：98K
- 年卷期：v.35,no.18(September 15, 2001)
- ISSN：1520-5851
文摘
For long-term performance assessment of nuclear wasterepositories knowledge concerning interactions of actinideswith mineral surfaces is imperative. The mobility andbioavailability of released radionuclides is strongly dependenton sorption/desorption processes onto mineral surfaces.Therefore it is necessary to characterize the surface speciesformed and to elucidate the reaction mechanisms involved.The high fluorescence spectroscopic sensitivity of Cm(III) has attracted our interest regarding the complexationprocess of Cm(III) onto smectite and kaolinite as amodel system for the sorption of trivalent actinides in thetrace concentration range. We conclude that at low pH Cm(III) is sorbed onto kaolinite and smectite as an outer-spherecomplex and retains its complete primary hydrationsphere. With increasing pH inner-sphere adsorption ontokaolinite and smectite occurs via the aluminol edge sites.The same evolution of the Cm(III)-clay surface speciesas a function of pH was observed for both minerals. Startingat a pH 
5 we observe the formation of a 
Al-O-Cm2+(H2O)5 surface complex, which is replaced by a secondspecies at higher pH. The second surface complex may bea monodentate Al-O-Cm+(OH)(H2O)4 species orbidentate (Al-O)2-Cm+(H2O)5 species. The Cm(III)/claysurface complexes are characterized by their emission spectra(peak maxima at 598.8 and 603.3 nm) and their fluorescencelifetime (both 110 ± 7 
s). An important result in viewof the mobility and bioavailability of radionuclides is thatno incorporation of Cm(III) into the bulk clay structure wasobserved.
5 we observe the formation of a Al-O-Cm2+(H2O)5 surface complex, which is replaced by a secondspecies at higher pH. The second surface complex may bea monodentate Al-O-Cm+(OH)(H2O)4 species orbidentate (Al-O)2-Cm+(H2O)5 species. The Cm(III)/claysurface complexes are characterized by their emission spectra(peak maxima at 598.8 and 603.3 nm) and their fluorescencelifetime (both 110 ± 7 s). An important result in viewof the mobility and bioavailability of radionuclides is thatno incorporation of Cm(III) into the bulk clay structure wasobserved.