Photochemical oxidation of Np(IV) in KHCO3 + K2CO3 solutions in the presence of Am(III)

Previously the authors have shown that Am(III) is photoxidized by water to Am(IV) in HCO3 + CO2-3 solutions. The potential of the Am(IV)/Am(III) couple in carbonate solutions is 0.99-0.81 V. Since the potentials of the Np(V)/Np(IV) and Np(VI)/Np(V) couples are 0.1 and 0.44 V, respectively, it is expected that Np(IV) would also be photooxidized in bicarbonate-carbonate solutions, Moreover, it was of interest to examine the neptunium behavior in the presence of Am(III), because Am(IV) formed upon photooxidation of Am(III) can additionally react with Np(IV) and catalyze its photooxidation