Adsorption of Eu(III) at rutile/water interface: Batch, spectroscopic and modelling studies

Abstract Knowledge of geochemical behaviors of Eu(III) in natural system is necessary for long-term safety assessment of deep radioactive waste repositories. The mobility or retention of the Eu(III) depends on its adsorption reaction at the mineral/water interface. Here, we studied the Eu(III) adsorption on rutile with batch experiments, zeta-potential analysis and time-resolved fluorescence spectra (TRFS). The results indicate that Eu(III) adsorption is controlled by outer-sphere interaction under acidic conditions, and transforms to inner-sphere interaction under neutral and alkaline conditions. A surface complexation model (SCM) from Rossendorf Expert System for Surface and Sorption Thermodynamics (RES3T) is successfully applied to describe the adsorption behavior of Eu(III) at the rutile/water interface with CHEMSPEC code. The good predictions indicate that the current SCM from RES3T could indeed be used for the estimation of Eu(III) adsorption on rutile surface, though it is not sensitive to the Eu(III) loadings. Overall, this work may provide valuable information on adsorption mechanism of Eu(III) at the rutile/water interface and help us understand the geochemical behaviors of Eu(III) in natural environments.