The role of surface-bound hydroxyl radicals in the reaction between H2O2 and UO2

• Published in: Journal of coordination chemistry 2018-07, Vol.71 (11-13), p.1799-1807
• Main Authors: Barreiro Fidalgo, Alexandre, Kumagai, Yuta, Jonsson, Mats
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Dependence; Dissolution; Hydrogen peroxide; Hydroxyl radical; Hydroxyl radicals; Kemi; Reaction kinetics; Reaction time; surface; Uranium; Uranium dioxide
• ISSN: 0095-8972; 1029-0389; 1029-0389
• DOI: 10.1080/00958972.2018.1466287

In this work, we have studied the reaction between H 2 O 2 and UO 2 with particular focus on the nature of the hydroxyl radical formed as an intermediate. Experiments were performed to study the kinetics of H 2 O 2 consumption and uranium dissolution at different initial H 2 O 2 concentrations. The results show that the consumption rates at a given H 2 O 2 concentration are different depending on the initial H 2 O 2 concentration. This is attributed to an alteration of the reactive interface, likely caused by blocking of surface sites by oxidized U/surface-bound hydroxyl radicals. The dissolution yield given by the amount of dissolved uranium divided by the amount of consumed hydrogen peroxide was used to compare the different cases. For all initial H 2 O 2 concentrations, the dissolution yield increases with reaction time. The final dissolution yield decreases with increasing initial H 2 O 2 concentration. This is expected from the mechanism of catalytic decomposition of H 2 O 2 on oxide surfaces. As the experiments were performed in solutions containing 10 mM and a strong concentration dependence was observed in the 0.2-2.0 mM H 2 O 2 concentration range, we conclude that the intermediate hydroxyl radical is surface bound rather than free.