Electrochemical Oxidation of Am(III) Ions in HNO3 Solutions

Formal oxidation potentials (E0^p) of the Am(IV)/Am(III) couple were measured and the kinetics of electrochemical oxidation of Am(III) on platinum electrode in concentrated solutions of nitric acid (1-6 M) containing potassium phosphotungstate K₁₀P₂W₁₇O₆₁ (KPW) was studied. The formal potential E0^p only slightly depends on the concentration of HNO₃ and is shifted toward the negative region by 1.0 V as compared with the standard values. The extent of Am(III) oxidation increases with increasing KPW concentration and decreasing concentration of nitric acid. Electrochemical oxidation of Am(III) is accompanied by radiochemical reduction of Am(IV) and is described by the equation -dC_Am(III)/dt = (k + k₁)C_Am(III) - k₁C₀ - k₀, where k is the apparent rate constant of electrochemical oxidation of Am(III), k₁ is the apparent rate constant of Am(IV) reduction, and k₀ is the constant of radiation-chemical reduction of Am(IV).