| Abstract: |
Due to their ubiquity in nature and chemical reactivity, aluminosilicate minerals play an important role in retarding actinide subsurface migration. However, very few studies have
examined Pu interaction with clay minerals in sufficient detail to produce a credible mechanistic model of its behavior. In this work, Pu(IV) and Pu(V) interactions with silica, gibbsite (Al-oxide), and Na-montmorillonite (smectite clay) were examined as a function of time and pH. Sorption of Pu(IV) and Pu(V) to gibbsite and silica increased with pH (4 to 10). The Pu(V)
sorption edge shifted to lower pH values over time and approached that of Pu(IV). This behavior is apparently due to surface mediated reduction of Pu(V) to Pu(IV). Surface complexation constants describing Pu(IV)/Pu(V) sorption to aluminol and silanol groups were developed from the silica and gibbsite sorption experiments and applied to the montmorillonite dataset. The model provided an acceptable fit to the montmorillonite sorption data for Pu(V). In order to accurately predict Pu(IV) sorption to montmorillonite, the model required inclusion of ion exchange. |
