Electrochemical Coreduction of Gd(III) with Pb(II) and Recovery of Gd from LiCl-KCl Eutectic Assisted by Pb Metal

Abstract

To recover Gd from LiCl-KCl eutectic, the coreduction mechanism of Gd(III) with Pb(II) was investigated using electrochemical methods. The formation potentials related to the formation of three Gd-Pb intermetallics were detected by cyclic voltammetry, square wave voltammetry and chronopotentiometry, and the formation mechanism of Gd-Pb compounds could be described as xPb(II) + 2xe− = xPb. Meanwhile, the electroreduction of Gd on liquid Pb electrode was explored. The diffusion coefficient of Gd metal in liquid metallic Pb was determined by anodic chronopotentiometry. The kinetic parameters of Gd(III)/Gd(in Pb) couple in the temperature range from 723 K to 873 K were determined employing linear polarization (LP) method. Based on the relationship of exchange current density and temperature, the reaction activation energy was estimated to be 23.17 kJ mol−1. In addition, the recovery of Gd from molten salts was performed assisted by liquid Pb electrode by constant potential electrolysis (CPE) and constant current electrolysis (CCE). The products characterized using XRD, SEM with EDS are comprised of GdPb3 and Pb phases. The concentration change of Gd during CCE process was monitored by ICP-AES, and the recovery rate was estimated. The results showed that Gd concentration decreased and recovery rate increased with the duration.