Viscosity of RE-bearing slag systems and kinetics of nucleation and growth for RE-phases

The RE-bearing slag with a considerable concentration of rare earths have attracted widespread attention in recent years, while the serious lack of basic data greatly limits its development and utilization. The viscosity of RE-bearing slag and kinetics for nucleation and growth of RE-phase are basic data which closely related to the mass transfer, separation and recovery of rare earths in the slag. However, the current reports on viscosity of RE-bearing slags are extremely scanty, and the existing viscosity models also have limitations due to the lack of thermodynamic data of rare earths. In this study, the viscosities of various RE-bearing slag systems (CaO–SiO2–Ce2O3, CaO–SiO2–CaF2–Ce2O3 and CaO–SiO2–CaF2–P2O5–Ce2O3) were firstly measured by the rotating cylinder method, and the change rules of viscosity for RE-bearing slag with CaF2 and P2O5 were reported. Moreover, the nucleation and growth kinetics of various RE-phases (calcium cerite, cefluosil, and britholite) were comprehensively studied, and the crystallization ability of RE-phases in RE-bearing slag was found to be cefluosil, followed by britholite and calcium cerite. The basic data reported in this study provide the necessary reference and guidance for recovery and utilization of rare earths in RE-bearing slag.