Spectrophotometric study of the behaviour of pertechnetate in trifluoromethanesulfonic acid: effect of alpha irradiation on the stability of Tc(VII)

This paper is devoted to the stability of pertechnetate in trifluoromethanesulfonic acid (HTFMS) in presence or absence of alpha irradiation. The irradiations were performed using alpha particles (4He²⁺) generated by ARRONAX cyclotron with an external beam energy of 70 MeV. The stability has been determined by UV–Visible spectroscopy. In the absence of alpha irradiation, the results have shown that Tc(VII) is reduced in HTFMS between 4 and 11 M. UV–Visible spectroscopy measurements in 4–8 M show the presence of one phase of Tc(IV) oxopolymeric species. At 9 M HTFMS, the change of UV–Visible spectrum with respect to lower concentrations suggests the formation of a second new species of Tc(IV). At highly concentrated HTFMS (11 M), the Tc(VII) species remains stable. These findings exhibit the formation of reduced Tc species by partial thermal decomposition and hydrolysis processes due to the highly exothermic hydration reaction of triflic acid with water. Under alpha irradiation, the same reduced Tc species as those observed without external irradiation were obtained with higher reduction kinetics. The formation of oxopolymeric technetium at important radiolytic yield resulted from reducing radiolytic products of both water and acid.