Voltamperometric determination of uranium and plutonium in alkaline solutions

Abstract

The simultaneous determination of U(VI), Pu(VI), Pu(V) in 0.5–4.0 M NaOH has been elaborated by means of classical and differential pulse voltamperometry. U(VI) is determined with a dropping mercury electrode (DME) at the half-wave potential of E_1/2=−0.89 V vs. Ag/AgCl reference electrode due to reduction to U(V). The limiting current or peak heights are proportional to uranium(VI) concentration in the range of 1.3.10⁻⁷–3·10⁻⁴ M U(VI). Deviation from proportionality is observed for higher concentrations due to polymerization of uranates. Pu(VI) and Pu(V) are determined with a platinum rotating electrode at E_1/2=−0.02 V due to the reaction Pu(VI)+e⁻»Pu(V) and with DME at E_1/2=−1.1 V due to the reduction to Pu(III). The limiting currents of both Pu(VI) and Pu(V) are proportional to their concentrations in the range of 4·10⁻⁶–1.2·10⁻³ M Pu. The determination of U(VI), Pu(VI), Pu(V) is not interfered by the presence of the following salts: 2M NaNO₃, 2M NaNO₂, 1.5M NaAlO₂, 0.5M NaF and ions of Mo(VI), W(VI), V(V), Cu(II). The presence of CrO ²⁻₄ and FeO ⁻₂ ions disturbs the determination of U(VI) in 1–4M NaOH, however, contribution of the reaction Fe(III)+e⁻»Fe(II) to uranium reduction peak can be calculated from the height of the second peak Fe(II)+2 e⁻»Fe(0).