Chemical thermodynamics of Technetium in the OECD/NEA Update Volume

Since publishing "Chemical Thermodynamics of Technetium" (1999RAR/RAN)about 20 years ago many new solubility studies with hydrous oxide of Tc(IV) have been undertaken and evidence for polymerization of Tc(IV) in aqueous solutions has strongly increased. New spectroscopic data have become available, leading to the spectroscopic confirmation of Tc(VII)/Tc(IV) and Tc(IV)/Tc(III) redox boundaries. This causes the need to reassess the chemical thermodynamics of Technetium in the frame of an update volume by OECD/NEA on the chemical thermodynamics of the actinides and technetium. In particular, hydrolysis schemes and chloride complexation are affected. Slow aging/dehydration of the hydrous oxide have been taken into account. No evidence for the existence of TcO⁺² has been found, leading to the rejection of thermodynamic data involving this species. (author)