Exploring the Reduction Mechanism of 99Tc(VII) in NaClO4: A Spectro-Electrochemical Approach

• Published in: Inorganic chemistry 2022-07, Vol.61 (26), p.10159-10166
• Main Authors: Rodríguez, Diana M., Mayordomo, Natalia, Parra-Puerto, Andrés, Schild, Dieter, Brendler, Vinzenz, Stumpf, Thorsten, Müller, Katharina
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.2c01278

Technetium (Tc) is an environmentally relevant radioactive contaminant whose migration is limited when Tc­(VII) is reduced to Tc­(IV). However, its reaction mechanisms are not well understood yet. We have combined electrochemistry, spectroscopy, and microscopy (cyclic voltammetry, rotating disk electrode, X-ray photoelectron spectroscopy, and Raman and scanning electron microscopy) to study Tc­(VII) reduction in non-complexing media: 0.5 mM KTcO4 in 2 M NaClO4 in the pH from 2.0 to 10.0. At pH 2.0, Tc­(VII) first gains 2.3 ± 0.3 electrons, following Tc­(V) rapidly receives 1.3 ± 0.3 electrons yielding Tc­(IV). At pH 4.0–10.0, Tc­(IV) is directly obtained by transfer of 3.2 ± 0.3 electrons. The reduction of Tc­(VII) produced always a black solid identified as Tc­(IV) by Raman and XPS. Our results narrow a significant gap in the fundamental knowledge of Tc aqueous chemistry and are important to understand Tc speciation. They provide basic steps on the way from non-complexing to complex media.