Abstract
<jats:p>In this study, an efficient three‑phase process was developed to upcycle rare earth elements (REEs) from spent fluorescent lamp phosphor. The method enables recovery of high‑value emitting materials without relying on conventional oxalate precipitation or high‑temperature calcination. Using methanesulfonic acid (MSA) as the lixiviant, the halophosphonate (HALO), yttrium‑oxide (YOX), and lanthanum‑phosphate (LAP) fractions were selectively leached into separate solutions. The YOX and LAP leachates were subsequently purified by quantitative iron removal. Because of the high aluminum content in the LAP leachate, it was further treated using 3D‑printed PA12/Amberlyst‑15 composite filters. The solid‑phase extraction (SPE) step consisted of adsorption followed by two desorption stages: (1) removal of impurities such as aluminum, magnesium, and boron with 1 M NH₄Cl, and (2) recovery of the LAP fraction, containing primarily La, Tb, and Ce, using 5 M MSA. After purification, both the YOX (Y, Eu) and LAP (La, Tb, Ce) fractions were precipitated using a synthesized α‑aminobis(phosphonate) ligand. The resulting precipitates exhibited high REE purities of 99.6±1.3% (YOX) and 98.9±1.4% (LAP). The REE–ligand complexes displayed the characteristic luminescence emission bands of Tb³⁺ and Eu³⁺, supporting their potential use in optical applications.</jats:p>