EXPERIMENTAL AND MODELED ADSORPTION OF RARE EARTH ELEMENTS IN YUCCA MOUNTAIN AQUIFER

Batch reactor experiments of certain rare earth elements and experiments of particle morphology are conducted for aquifer material in Yucca Mountain. Through the experiments, high-quality hydrogeologic and geochemical parameters are derived for developing a surface complexation model. Subsequently, the PHREEQC is used for parameter evaluation under different temperatures, redox potentials and pHs. The FITEQL is used to optimize experiment-derived parameters (i.e., complexation constant) with the least squares fitting optimization procedure. After the analysis of adsorption isotherms, different surface complexation models (SCMs) are used to model adsorption for the aquifer in Yucca Mountain. Through comparisons, a proper SCM is selected for further numerical simulation of solutes and flow transportation. This study would help us better understand the geochemical reactions of REEs and provide a preliminary linkage between experiments and numerical modeling.