Investigation of the process for aggregate formation with the reduction of uranium

Ouchi, Kazuki  ; Otobe, Haruyoshi  ; Kitatsuji, Yoshihiro  

In this study, we investigated the relationship between reduction process and formation of aggregates by measuring electrochemical quartz crystal microbalance (EQCM). When EQCM measurements of the reduction of U(V) to U(IV) in weakly acid solution were performed, the frequency was changed negatively. This indicates that aggregates of U(IV) were formed on the electrode. We consider that aggregates form in the three steps from the deposition rate; the induction step ( start deposition), early stage aggregation step (deposition amount 4 nmol) and secondary stage aggregation step (deposition amount 4 nmol). The pH dependence of the reduction and deposition rate was investigated. The U(IV) aggregates formed at more than pH3.1. When pH was higher, the induction time was fast, and aggregation rates at early and secondary stage were high. This suggests that a U hydroxide relates to the formation of aggregates.