The surface reactions of U(VI) on γ-Al2O3 In situ spectroscopic evaluation of the transition from sorption complexation to surface precipitation


The surface reactions of U(VI) on γ-Al2O3 In situ spectroscopic evaluation of the transition from sorption complexation to surface precipitation

Müller, K.; Foerstendorf, H.; Rossberg, A.

Aluminates, representing an essential component of clay minerals, play a decisive role in regulating the mobility of contaminants in rock and soil formations, in particu-lar due to their tendency to form coatings on mineral surfaces [1].
In this work, U(VI) sorption on γ-Al2O3 is comparatively investigated using in situ vibrational and X-ray absorption spectroscopy. The focus was set to micromolar U(VI) concentrations and a variety of environmentally relevant sorption parameters in order to resolve discrepancies reported earlier [2-4].
Time-resolved (TR) IR spectroscopic sorption experiments at the alumina-water in-terface evidence the formation of three different species as a function of surface loading (c.f. Fig.): a monomeric carbonate complex, an oligomeric surface complex and a surface precipitate. These results are confirmed by IR experiments performed at different flow rates, pH values, ionic strengths, U(VI) concentrations, and in inert gas atmosphere. Results of EXAFS experiments of batch samples are consistent to these findings [5].

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Publ.-Id: 24078