Speciation of technetium and rhenium complexes by in situ XAS-electrochemistry

A spectro-electrochemical cell was developed in order to study the speciation of radio-elements in thermodynamic unstable redox states using in situ XAS spectroscopy. This cell was used for the speciation of Re and Tc complexes in chloride media. Experiments on Re were carried out with the aim to validate the functionality of the experimental set-up. During electro-reduction of Re(VII) in HCl media, EXAFS and XANES studies were performed in order to reveal the formation of chloro-oxygenated compounds of Re(IV). The speciation of technetium in aqueous solutions of deep geological deposits for radioactive waste is important to predict its mobility under reducing conditions. XANES spectra showed that electro-reduction of Tc(VII) in chloride media leads to a position of K-edge absorption which agrees with a Tc(IV)/Tc(III) mixture