Intermediate oxidation states of technetium in alkaline solutions

The electrochemical reduction of pertechnetate ions (TcO4−) have been studied in strongly alkaline media (0.3 ÷ 10 M aqueous NaOH) using electrochemical (cyclic voltammetry (CV); chronoamperometry (CA), chronopotentiometry (CP)) and spectroelectrochemical (UV-Vis OTTLE and Au-SERS) techniques. Such obtained results show formation of two types of Tc(V) species as intermediates in the electrochemical reduction of the pertechnetates. The soluble Tc(V) forms, detected by means of UV-Vis measurements are relatively stable but disproportionate to Tc(IV) and Tc(VII). The other type of Tc(V) containing products is present at the electrode surface. The latter species were detected and characterized by a band at 700 cm−1. The final products of the multistep reduction of the pertechnetates in NaOHaq are Tc(IV) compounds which composition depends on the electrolyte concentration. Thus, insoluble and adsorbed in the electrode surface TcO2 is the main product in 0.3 M NaOH while soluble polymeric Tc(IV) are the prevailing species observed in 10 M NaOH.