Selective Electrochemical Separation and Recovery of Uranium from Mixture of Uranium(VI) and Lanthanide(III) Ions in Aqueous Medium.

Abstract

Separation of uranium (U) from interfering lanthanide ions (Ln3+) in aqueous medium is important in view of sustainable nuclear power production and remediation of radioactive waste. Separation of U in aqueous medium by electrochemical means is still unexplored. Herein, we report electrochemical separation of U from interfering lanthanides ions in 0.1 M KCl on poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) modified platinum (PEDOT:PSS/Pt) electrode. U in solution commonly exists as uranyl (UO22+). U separation is achieved in a two step process: (i) UO22+ reduction to insoluble urania (UO2) which gets deposited on PEDOT:PSS/Pt in the presence of Ln3+ (La3+, Ce3+, and Sm3+) ions and (ii) oxidation of electrodeposited UO2 to UO22+ in fresh 0.1 M KCl (pH = 2) solution. Electrodeposition of UO2 is confirmed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Although, the presence of Ln3+ ions in UO22+solution hinders electrodeposition of UO2, but application of more negative reduction potential (-0.6 V vs Ag/AgCl) for longer duration (8 h) results in quantitative electrodeposition of UO2. Inductively coupled plasma mass spectrometry (ICP-MS) shows that 94% (±10%) recovery of UO22+ is possible from mixed solution of UO22+and Ln3+ ions on PEDOT:PSS/Pt electrode.