Surface complexation modeling for description of actinide sorption at the buffer materials/water interface

Abstract

As mechanistic modeling becomes more feasible, surface complexation modeling was applied to actinide sorption reactions with the edge-surface hydroxyl groups of montmorillinite contained in bentonite, which is a potential buffer material for radwaste disposal. The determined surface properties of Japanese bentonite samples suggested possible interactions between positively charged surface sites and anionic Np(V) species in alkaline pH region under high inorganic carbon concentration conditions. The interfacial capacitance density affected determination of the bentonite surface parameters and the Np(V) surface complexation constants. The valence of the aqueous sorbing species was clarified to be useful in determining surface complexation constants of actinide sorption.