Mechanism of the electrochemical reduction of TcO/sub 4//sup -/ in alkaline media

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5030281

Founta, A

The electrochemical reduction of TcO/sub 4//sup -/ in non-complexing media, in the pH range 8 to 14 was studied with the techniques of sampled dc, normal pulse and reverse pulse polarography. The experimental conditions under which TcO/sub 4//sup 2 -/ is observed were established, and a mechanism is reported for its further reduction to Tc(V) in the pH range 9 to 12. The mechanism for reduction to Tc(V) is supported by the good agreement of the limiting currents, half-wave potentials and log plot slopes with the predictions of a digitally simulated ECE mechanism. The TcO/sub 4//sup -//TcO/sub 4//sup 2 -/ reduction is reversible on a time scale of 3 msec and is pH independent. Its E/sup 0/ is estimated to be -0.88 V vs. SCE. The disproportionation of Tc(VI) is not an important part of the mechanism of the two-electron reduction of TcO/sub 4//sup -/ in the pH range 10 to 13, at ionic strength below 0.1 M and TcO/sub 4//sup -/ concentrations below 5 x 10/sup -4/ M. Disproportionation of Tc(V) above pH 12 which is accelerated by hydroxyl ions leads to its further reduction to Tc(IV). A mechanism is proposed that accounts for the three electron reduction of TcO/sub 4//sup -/ in strongly alkaline media. The electroreduction of TcO/sub 4//sup -/ in the presence of ammonia and citrate is kinetically controlled at about pH 10. Ammonia and citrate apparently complex Tc(V) and lead to its further reduction to Tc(IV).

• Research Organization: Rensselaer Polytechnic Inst., Troy, NY (USA)
• OSTI ID: 5030281
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400* -- Electrochemistry
CHEMICAL REACTIONS
CHEMISTRY
ELECTROCHEMISTRY
OXYGEN COMPOUNDS
PH VALUE
REDUCTION
REFRACTORY METAL COMPOUNDS
TECHNETATES
TECHNETIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS