Recovery of Rare Earth Elements from Wasted Lamp Phosphor Using Deep Eutectic Solvents

In this study, two deep eutectic solvents were used to realize the comprehensive recovery of high-value rare earth elements from wasted lamp phosphors. Firstly, 99.38% of Y and 93.12% of Eu in the phosphor waste were leached by using the hydrophilic deep eutectic solvent (betaine-propanedioic acid) under the conditions of 20% water content, leaching temperature of 90 ℃, leaching time of 16 h, and solid-liquid ratio of 75∶1 (mL/g), and the recovery of Y and Eu was realized by the oxalic acid precipitation method. And then, the extraction and separation of rare earth elements (Tb, Eu, Ce) and impurities (Al, Ba, Mg) in the second-stage alkali-melt leach solution was realized by using the hydrophobic deep eutectic solvent (thenoyltrifluoroacetone-trioctylphosphine) under the initial aqueous phase pH of 1, O/A of 0.8, and a shaking time of 12 min. The rare earth elements loaded in the hydrophobic deep eutectic solvent could be stripped by using 5 mol/L HCl to obtain the chlorinated rare earth enrichment solution, and the performance of the hydrophobic deep eutectic solvent was basically unchanged after five cycles. This process realizes high-efficiency and low-cost selective recovery of high-value rare earth elements from waste lamp phosphors, and has excellent application prospects in the field of secondary resource recovery of rare earths.