Abstract:A process of magnetic separation, roasting, and leaching was proposed to extract rare earth elements from molten salt electrolytic slag. The results of the full process examination show that iron removal efficiency of the raw material is 45.59% under the optimal magnetic separation strength of 100 mT. The optimal process conditions of the non-magnetic phase in the roasting and leaching process include roasting temperature of 750 ℃, CaO dosage of 30%, leaching temperature of 25 ℃, and HCl concentration of 3 mol/L. The total recoveries of Nd and Pr reach 95.98% and 96.15% respectively in the whole process. The in-situ XRD combined with thermodynamic analysis was used to clarify the mineral phase transformation law during roasting. It is found that during the roasting process, REF3 reacts with CaO to form REO, while CaCl2 reacts with CaO and REF3 to form REOCl, which further transforms into REO. Increasing roasting temperature can reduce the formation of insoluble phase REOCl and promote transformation of REF3 to soluble phase REO, thus increasing the leaching efficiency of rare earth. This study can provide theoretical guidance for the recovery of rare earth.