Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) Study of the Sorption of Cm(III) onto Smectite and Kaolinite


Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) Study of the Sorption of Cm(III) onto Smectite and Kaolinite

Stumpf, T.; Bauer, A.; Coppin, F.; Kim, I. J.

The surface sorption process of Cm (III) onto smectite and kaolinite was investigated by time-resolved laser fluorescence spectroscopy (TRLFS) in the trace concentration range. We conclude that at low pH Cm(III) is sorbed onto kaolinite and smectite as an outer-sphere complex and retains its complete primary hydration sphere. With increasing pH, inner-sphere adsorption onto kaolinite and smectite occurs via the aluminol edge sites. The same evolution of the Cm(III)-clay surface species as a function of pH was observed for both minerals. Starting at a pH ³ 5, we observe the formation of a ºAl-O-Cm2+(H2O)5 surface complex, which is replaced by a second species at higher pH. The second surface complex may be a monodentate ºAl-O-Cm+(OH)(H2O)4 species or bidentate º(Al-O)2-Cm+(H2O)5 species. The Cm(III)/clay surface complexes are characterised by their emission spectra (peak maxima at 598.8 nm and 603.3 nm) and their fluorescence lifetime (both 110±7 µs). An important result for the mobility and bioavailability of radionuclides is that no incorporation of Cm(III) into the bulk clay structure was observed.

  • Environmental Science and Technology

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Publ.-Id: 3640