Phase equilibrium of the CaO–SiO2–Al2O3–Ce2O3 system: A basis for recovering REEs from RE-Containing slag

Abstract

With the massive consumption of rare earth resources, the recovery of rare earth elements (REEs) from secondary resources has become a focus of attention. It is economically necessary to recover REEs from Bayan Obo RE-containing blast furnace slag (RE-BFS), which contains considerable REEs. However, due to the lack of relevant thermodynamic data, it is difficult to effectively recover REEs from RE-BFS. Therefore, the isothermal phase diagram of CaO–SiO2–Al2O3–Ce2O3 at 1100 °C was constructed in this work, according to the principle of phase diagram construction combined with the method of equilibrium experiments. The optimal rare earth equilibrium phase in this system was defined as Ce4.667-xCax(SiO4)3O1-0.5x. According to the actual composition of the RE-BFS, a dominant separation region of L + Ce4.667-xCax(SiO4)3O1-0.5x was obtained in the phase diagram. Subsequently, the extraction of REEs in the RE-BFS could be completed by solid–liquid separation, which allowed economic benefits without affecting the environment. The data reported in this work provide a theoretical basis for solving the problem of recovery from RE-containing secondary resources and developing high value-added materials.