A "Two-Step" Electrochemical Approach for Recovery of Plutonium and Uranium from Aqueous Acidic Waste Solutions

Chemical quality control of nuclear fuel, particularly the determination of Pu and U contents by chemical methods, results in analytical acidic aqueous waste solutions from which Pu and U must be recovered efficiently for the remediation of radioactive wastes. Reported methods involve several complicated steps requiring addition of chemical oxidants/reductants for valence adjustments and generation of secondary wastes, thereby making the recovery process cumbersome. Herein, we report a novel two-step electrochemical approach for Pu and U recovery from acidic aqueous waste solutions containing different metallic impurities (Fe, Cr, Mn, Cd, Al, Ni, Co, Zn, and Mg) by bulk electrolysis using a Pt gauze electrode. Pu and U are recovered from these waste solutions in a two-step process: (i) bulk electrolysis of the mixed solution at a constant potential of 0.1 V vs Ag/AgCl/3 M KCl that results in the reduction of PuO₂²⁺ to Pu³⁺ followed by the precipitation of Pu³⁺ as K₂(K_0.5Pu_0.5)(SO₄)₂, which is then filtered and separated and (ii) the filtrate solution is again subjected to bulk electrolysis at a constant potential of -0.35 V vs Ag/AgCl/3 M KCl resulting in the reduction of UO₂²⁺ to U⁴⁺. The U⁴⁺ is then precipitated as K₂(K_0.67U_0.33)(SO₄)₂, which is filtered and separated, leading to a Pu- and U-free aqueous acidic waste solutions. Biamperometry shows that 97.8% and 99.1% recovery of Pu and U, respectively, is possible, and emission spectrometry confirms the purity of K₂(K_0.5Pu_0.5)(SO₄)₂ and K₂(K_0.67U_0.33)(SO₄)₂. Because of its operational simplicity, potential for remote handling, and excellent extraction efficiency, the present methodology can easily replace traditional methods for the recovery of Pu and U from acidic aqueous waste solutions.