Adsorption of Transition Metal Cations on B75 Bentonite and Behavior of the Glass/Copper/Bentonite Barrier System under Simulated Repository Conditions

Abstract

Since plans for a future deep geological repository (DGR) site have been published in Hungary, further study of their material characteristics has become essential to understand how to operate and design them properly fully. The main goal of this study is to understand the retention of cations (Ni(II) and Co(II)) by the B75 bentonite through adsorption and desorption experiments and the interactions between materials of the glass/copper/bentonite model system under repository conditions. The obtained adsorption and desorption isotherms show irreversible sorption of both ions at higher concentrations (above 10^–5 M), where the difference is higher in the case of the Ni(II) ions than for Co(II) ions. The surface study of the borosilicate glass shows an increasing trend in the concentration of Zr and O, and a decrease in the case of Si, Ba, Na, and B, showing an equilibrium state from the beginning. The surface of different physical shapes of copper (rod, tape, sliver) shows differences in the case of the rod; higher C and lower O amounts were found, which indicates the formation of Cu₂O; however, the difference between the samples was not influential. Based on the inductively coupled plasma-optical emission spectrometry, the concentration of elements in the pore water solutions was determined. The release of B, K, Na, and Si increased throughout the experiment; in contrast, the concentrations of divalent cations (Ca and Mg) decreased throughout the measurement. No copper dissolution was detected.