Sequential one-electron reduction of Fe(V) to Fe(III) by cyanide in alkaline medium

The reduction of Fe(V) by cyanide has been studied anaerobically in alkaline media (pH 10.55-12.10) by using a premix pulse radiolysis technique. The results demonstrated for the first time the spectroscopic evidence for sequential one-electron reductions of Fe(V) to Fe(IV) to Fe(III) in aqueous media. Rates for reductions decrease with an increase in pH and appeared to be related to deprotonation of Fe(V) and Fe(IV) species. The reactivity of the three ferrates (Fe(VI), Fe(V), and Fe(IV)) with cyanide showed that Fe(V) and Fe(IV) are approximately four- and two-orders of magnitude more reactive than Fe(VI), respectively. These rates suggest that Fe(VI) oxidations of compounds may be accelerated if reactions are performed in the presence of one-electron or two-electron reducing substrates.