TMPAC-EG deep eutectic solvent for sustainable recovery of Nd by electrodeposition

The electrodeposition of neodymium (Nd) in a novel analogous ionic liquid (AIL), phenyltrimethylammonium chloride-ethylene glycol (TMPAC-EG), was investigated. The existence form and the electrochemical behavior of Nd(III) in TMPAC-EG were studied using spectroscopic, cyclic voltammetry and chronoamperometry analyses. The spectroscopic analyses indicates that Nd3+ interact with Cl_and EG to form complexes [Nd(EG)6-yCly]3-y as NdCl3 dissolves in TMPAC-EG IL. Cyclic voltammograms reveals that the overpotential for Nd electrodeposition in TMPAC-EG IL decreases with the rise of the temperature. The diffusion coefficient of Nd(III) ions is calculated to about 10_12 m2 s_ 1. The diffusion activation energy for Nd(III) ions is determined to be 22.8 kJ mol_ 1 from the temperature dependence of diffusion coefficient. The transient analysis indicates that initial nucleation behavior of Nd conforms to the three-dimensional instantaneous nucleation and growth model, which are largely independent of temperature. In addition, deposition temperature and deposition potential are found to have a great influence on the nucleation and growth kinetics of Nd electrodeposition. Depending on the temperature and potential of electrodeposition, metallic neodymium with caterpillar-shape, nodule, layered rock, or porous structures was obtained.