Application Case Sorption onto Rocks

The SCM concept combined with a powerful sorption database allows a straightforward extension towards rocks and soils composed of several minerals. Their sorption behaviour should be predicted from the weighted superposition of the sorption processes for all constituting minerals. The number of important rock-forming minerals is rather limited, more then 95 % of the known rocks in the earth s crust consist of only about 20 minerals and mineral groups (Ronov and Yaroshevsky, 1967). Thus we hypothesized that the sorption behaviour of uranium(VI) onto rocks can be described 

The studied phyllite is composed of 48 vol.% quartz, 25 vol.% chlorite, 20 vol.% muscovite, 5 vol.% albite feldspar, and 2 vol.% opaque material, mostly rutile, magnetite, and traces of hematite. The basis for the successful interpretation of the experimental sorption data of uranium(Vl) on phyllite were  

The surface complex formation constants and the protolysis constants were optimized by using the experimentally obtained data sets and the computer code FITEQL (Herbelin and Westall, 1996). Surface site densities were evaluated from adsorption isotherms at pH 6.5 and a total uranium concentration of 1x10 M. The formation of ferrihydrite during the batch sorption experiment was identified by Mossbauer spec- 

FITEQL calculations were carried out for a composite phyllite which was constructed from the respective mineral components quartz, chlorite, muscovite, and albite in their relative proportion within the phyllite, and in addition with the newly forming phase ferrihydrite. 

The modelling indicated that uranium(VI) sorption to ferrihydrite clearly dominates the uranimn(VI) sorption on phyllite showing the great importance of secondary iron phases for sorption studies. 

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