Reduction of pertechnetate by ferrous iron in solution: Influence of sorbed and precipitated Fe(II)

The reduction of TcO4- to TcO2 . nH(2)O by Fe(II) in slightly acid to basic solution has been investigated in an all-glass reaction vessel with a hydrophobic inner surface. The three-electron reduction process, although thermodynamically feasible, was found to proceed very slowly if at all. Fe(II) sorbed on the wall of untreated reaction vessels or precipitated as Fe(OH)(2)(s) or FeCO3(s) was found to reduce TcO4-, the observed rates being proportional to the amount of sorbed or precipitated Fe(II). The experimental results are discussed in light of the standard redox potentials and possible reaction paths leading from TcO4- to TcO2 . nH(2)O.