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|Title:||SYSTEMATIC EVALUATION OF Tc(VII)/Tc(IV) REDOX PROCESSES IN 0.1 M NaCl SOLUTIONS|
|Authors:||KOBAYASHI Taishi; GAONA Xavier; FELLHAUER David; ALTMAIER M.|
|Citation:||3rd Annual Workshop Proceedings of the Collaborative Project "REdox Phenomena Controlling Systems" (7th EC FP CP RECOSY) p. 137 - 146|
|Publisher:||Karlsruher Institut fuer Technologie|
|Type:||Articles in periodicals and books|
|Abstract:||The reduction of 1·10−5 mol/dm3 (M) Tc(VII) solutions in various reducing systems (homogeneous solutions with inorganic and organic reductants and heterogeneous suspensions containing Fe(II)/Fe(III) precipitates and Fe powder) was investigated in the pH range 2 – 13 in 0.1 M NaCl/NaOH at 22ºC under Ar atmosphere. The results were systematized according to Eh/pH conditions in solution and a general borderline for the reduction of Tc(VII) to Tc(IV) regardless the reducing systems was obtained according to the reaction (TcO4 – + 4H+ +3e– = TcO2(coll,hyd) + 2H2O). This experimental borderline was (about 100 mV) lower than the equilibrium line for the reduction of Tc(VII) (log [Tc(VII)]tot = −5.0) calculated from reported standard redox potential of TcO2(s) prepared electrochemically. This possibly implies the existence of more soluble solid phases such as small Tc(IV)oxyhydroxide particles under the given conditions. Reaction kinetics are also discussed and correlated to the measured redox potentials and the reduction borderline.|
|JRC Directorate:||Nuclear Safety and Security|
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