It is very important to develop the recycle process for rare earth metals from the standpoint of environmental-friendly and saving-energy. We have already demonstrated that an economic recycle process of the rare earths from the waste of neodymium-based magnets. This study in rare earths recycle process was focused on the separation of the iron group metal and the recovery of the rare earths using a novel ionic liquid. In addition, this phosphonium-based ionic liquid was adaptable as an electrodeposition media for the recycle process because this kind of ionic liquid is unique physicochemical properties such as low viscosity and high electrochemical stability. The electrochemical and the diffusive properties of the iron complex were investigated from linear sweep voltammetry and chronoamperometry. The diffusion coefficient of Fe(II) was estimated to be the order of 10−11 m2 s−1 at 100°C. It was also revealed that the nucleation process of Fe(II) was proceeded on the instantaneous nucleation from Scharifker model. The overpotential of the nucleation process for Fe(II) was decreasing with elevating the bath temperature of the ionic liquid. Moreover, the selective separation of the iron metal was effectively possible for the electrodeposition at the constant potential. Furthermore, the electrodeposition in ionic liquid bath was allowed us to recover the neodymium metal at highly efficient.
