Research on the Mechanism and Process Optimization for Efficient Recovery of Rare Earth Elements from Waste Light-Emitting Diodes

With the rapid development of semiconductor lighting technology, the amount of waste light-emitting diodes (LEDs) has increased continuously, making the rare earth elements contained in LED phosphors, such as Y, Eu and Tb, an important secondary resource. However, these elements are usually incorporated into phosphor lattices in stable doped forms, and their high lattice energy and complex multiphase structures greatly hinder efficient recovery. This study focuses on the recovery of rare earth elements from waste LEDs and systematically analyzes their occurrence characteristics, interfacial dissociation behavior, migration mechanisms, selective leaching, and separation processes. A theoretical framework covering structural decomposition, interface liberation, selective dissolution, and purification is established to support the high-value utilization of critical resources from complex electronic waste.

The results indicate that the synergistic effect of thermal treatment and chemical pretreatment can significantly weaken interfacial bonding, reducing the bonding strength from about 12.3 MPa to below 3.0 MPa and increasing the phosphor exposure rate to over 80%. Under optimized leaching conditions of 85.0–90.0 ℃ and 3.8–4.4 mol·L⁻¹ acid concentration, the release rate constant of rare earth elements exceeds 0.045 min⁻¹, while the apparent activation energy decreases to approximately 40.0 kJ·mol⁻¹, indicating a transition from diffusion control to interfacial reaction control. In complexing systems, increasing the stability constant to logK≈2.3 effectively suppresses hydrolysis and promotes continuous dissolution. Furthermore, a multistage recovery process enables rare earth recovery efficiencies of 93.0%–95.0%, with impurity dissolution below 22.0%. Coupled solvent extraction, adsorption, and ion exchange achieve separation efficiencies above 90% and product purity exceeding 99.5%. Process integration further reduces energy consumption by approximately 18.0% and improves reagent utilization to over 75.0%.