Recovery of Rare Earth Elements from Waste Phosphate-Based Phosphors Containing Glass by Pre-Enrichment—Alkali Roasting Method

Based on the physicochemical properties of waste phosphate-based rare earth phosphors containing glass, this paper proposes a novel recovery method for rare earth elements (REEs) that integrates pre-enrichment, alkali roasting, and enhanced leaching. Initially, preliminary enrichment of REEs was achieved through sieving to remove silicon (from glass components) and pickling to reduce calcium content (originating from calcium phosphate compounds). The enriched material was then subjected to alkaline roasting, followed by washing for impurity removal, hydrochloric acid leaching, and finally oxalic acid precipitation to extract the rare earth elements. Experimental results demonstrate that the overall recovery rate of rare earth oxides (REO) reached 96.6%, indicating highly efficient extraction and separation of REEs from the waste phosphors. Furthermore, the mechanism of the alkali roasting process was investigated via differential thermal analysis (TG-DSC). Microstructural and phase changes in the waste phosphors before and after roasting were systematically characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that green phosphor (REPO₄) was converted into rare earth oxides and water-soluble sodium phosphate under alkaline roasting conditions. The Na₃PO₄ could be effectively removed through washing, while the rare earth elements were retained in the form of oxides within the washed residue. This study provides an important theoretical foundation and technical approach for the efficient recovery of rare earth resources from waste phosphate-based phosphors.