Sorption behaviour of radioactive nuclides (e.g. U, Np, Ln(III)) with natural minerals (muscovite and orthoclase)
Thermodynamic data for the sorption of actinides (e.g. U, Np) on different mineral surfaces (mica, especially muscovite; feldspar, especially orthoclase) should be appointed by means of experimental work. Thereby for Np and U the sorption of different oxidation states on these minerals should be examined to get some information about the redox behaviour. (Additional work with Ca as competition cation is done, that represents an important groundwater component.) At the beginning experiments start with a binary system and afterwards it will be supplemented by anionic ligands or cationic competition metals.
Beside conventional batch experiments as a function of pH, actinic-concentration, ionic strength and liquid to solid ratio in combination with already implemented methods (ICP-MS, LSC) with detection limits at the range of tracers, a lot of microscopic and spectroscopic methods will be used. Thus the characterisation of solid particles can be done by BET, XRD and AFM. In addition laser induced spectroscopy (TRLFS), UV/Vis-Spectroscopy, oscillation spectroscopy (ATR FT-IR, Raman) and x-ray absorption spectroscopy is available. This should be used to determine the speciation and structure of possible surface complexes and to generate reaction equations that can be implemented in surface complexation models.