Recovery of rare earths, lithium, and fluorine from rare earth molten salt electrolytic slag by mineral phase reconstruction combined with vacuum distillation

A novel green method for the recovery of rare earths (REs), fluorine (F), and lithium (Li) from rare earth molten salt electrolytic slag (REMSES) was proposed and demonstrated by mineral phase reconstruction combined with vacuum distillation. Kinetic analysis revealed that the roasting process was controlled by the chemical interface reaction. Under the optimized conditions (roasting temperature of 600 degrees C, LiOH center dot H2O dosage coefficient of 1.1 times, and roasting time of 4 h), NdF3 and NdOF in the slag were almost completely converted to LiF and Ca2Nd8(SiO(4))6O(2). The removal rate of F and recovery rate of LiF were 99.98 % and 98.96 %, respectively, at 1100 degrees C and 10 Pa for 1 h, indicating that F could be effectively removed by vacuum distillation. The F and Li were recovered as LiF with a purity of 99.8 wt%, which could then be recycled in the molten salt electrolysis process for the preparation of RE metals. The leaching rate of TREO from distillation residue was 99.27 % using hydrochloric acid. This process not only successfully achieved the green and efficient recovery of REs, Li, and F from REMSES, but also eliminated environmental pollution caused by the release of F.