Selective recovery of Y and Eu from rare-earth tricolored phosphorescent powders waste via a combined acid-leaching and photo-reduction process

Rare-earth tricolored phosphorescent powders (RETPPs) waste is a prime target for recovery of the scarcest, highest-market-value, and most important rare-earth elements, such as yttrium and europium. Thus, in this study, we assessed a two-step method for the selective recovery of Y and Eu from the RETPPs waste. The method involves an acid-leaching step using an “HCl + H2O2” system to yield a Y-Eu solution, followed by photo-reduction with (NH4)2SO4 to precipitate Eu as EuSO4. We optimized the conditions of each step. Acid leaching was best performed with 1 mol/L HCl in the presence of 2 mL H2O2 (per 500 mL) at 50 °C for 4 h, resulting in high Y (99.9%) and Eu (61.2%) yields with relatively low impurities. Photo-reduction was best performed with (NH4)2SO4 concentration of 50 mM, pH ∼4, and irradiation with a 254-nm ultraviolet lamp irradiation for 42 h, resulting in a 98.5% yield of high-purity (96.7%) EuSO4. These findings can help improve secondary resource recovery technologies for rare-earth elements.