This study mainly focused on the thermodynamic evaluation on the recyclability of various rare metals. Totally, recycling of end-of-life (EoL) nickel, cobalt, nickel-cobalt based alloy, titanium, zinc, and silicon products was considered. During the recycling, the alloying elements contained in EoL products are always treated as impurity elements, and the removability/controllability of them was quantitatively evaluated using thermodyanmic method in present study.
1. Following the thermodynamic evaluation on refinability of EoL Ni- and Co-based superalloys by remelting process carried out in 2014 (H. 26), the activity coefficients of NiO and CoO in CaO-Al2O3-SiO2 slag were measured by metal/slag/gas equilibrium experiments to provide fundamental thermodynamic information for the control of Ni-Co-based solvent alloy using remelting process. Controlling the basicity of CaO-Al2O3-SiO2 slag close to unity is found helpful to remove the contained iron and reduce the oxidation losses of nickel and cobalt during remelting of EoL superalloys. The controllability of Ni-Co-Fe alloy composition using CaO-Al2O3-SiO2 slag was evaluated based on present results.
2. The refinability of silicon using slag treatment and directional solidification processes was evaluated by thermodynamic method.
3. The removability of aluminum and vanadium from EoL titanium by evaporation of sub-oxides was thermodynamic evaluated.
4. Following the thermodynamic evaluation on the refinability of EoL zinc in H.26, the distribution of iron and lead between chloride slag and zinc was experimentally measured.