Selective extraction and recovery of rare earth metals from waste fluorescent powder using alkaline roasting-leaching process

Waste management of rare earth metals (REMs) containing materials and recycling of rare earth metals (REM) from waste materials are becoming more and more important due to high demand and resource exhaustion. However, extraction of REM from waste fluorescent powder materials is difficult because of their special aluminate structure. A novel "alkaline roasting-acid leaching" process was developed in this study. The alkaline roasting process mechanism was examined using differential thermal analysis (DTA)-thermogravimetric (TG) measurements, and the roasting product was characterized by XRD analysis. In this process, Al2O3 was converted into water soluble NaAlO2 via alkaline roasting, and NaAlO2 in the roasting product could be easily dissolved in water, while the rare earth oxide (REOs) remained as solid. After filtration, REOs cake was leached using hydrochloric acid to achieve 99.8% of REM recovery. It was concluded that the alkaline roasting-acid leaching process could effectively separate Al2O3 and REOs with high REM recovery.