Adsorption of Cations on Mineral-Aqueous Solution Interface at Elevated Temperatures

Kubicki/Lvov

EAR-0073722

Experiments and molecular simulations will be performed in parallel to examine the behavior of mineral surface charge, zeta potential and adsorption in aqueous solutions at elevated temperatures. Numerous research groups are currently working on these phenomena; however, almost no data exists for these parameters at elevated temperatures up to 300 degrees C. The method to be employed is microelectrophoresis for determination of electrical mobilities of oxide particles. The minerals chosen for this study are corundum and zircon. Water flow through the crust near radioactive waste storage facilities and in hydrothermal areas occurs in the temperature range of this study. Knowledge of the surface charge and zeta potential with temperature are critical for predicting adsorption behavior of ions because a change in sign can signal a shift from adsorption to desorption. Understanding adsorption behavior is in turn key to the ability to predict the migration of contaminants in the subsurface. Due to difficulties in assessing the positions of ions near a mineral surface in situ under high temperature conditions, molecular simulations are a valuable companion to the experimental component of this research. Both quantum and classic mechanical simulations of surfaces, water and counterions are planned. By linking experiment and theory via the measured and simulated points-of-zero charge and zeta potentials, the structure of counter-ions near a surface may be reliably modeled. Molecular simulations provide insight into the amount of adsorption likely to take place and the mechanisms of adsorption that control the kinetics of ions near surfaces.