An Integrated Leach–Extract–Strip Process for Yttrium Recovery from Spent Fluorescent Lamps: Kinetic Assessment and Solid–Liquid Extraction with D2EHPA-Impregnated XAD-7

Growing demand for rare earth elements (REEs) necessitates the development of efficient recycling strategies from secondary sources. This work presents a complete hydrometallurgical process for recovering yttrium (Y) from spent fluorescent lamps, emphasizing the efficient coupling of a conventional acid leaching with a solid–liquid extraction system. Multi-stage sulfuric acid leaching (2 M, 65 °C, an S/L ratio of 0.25 g/L) achieved a cumulative yttrium dissolution of 71.11% over four stages, with individual stage recoveries (based on initial yttrium content) of 44.2%, 21.56%, 7.19%, and 0.68%. Kinetic and spectroscopic analyses (FTIR, SEM-EDS) revealed that the leaching rate is controlled by diffusion through an in situ formed sulfate-rich layer (CaSO4, Na2SO4), as described by the Z-L-T (Zhuravlev–Leshokin–Templeman) model (Ea = 35.5 kJ mol−1). The resulting leachate was subjected to solid–liquid extraction using Amberlite XAD-7 resin impregnated with D2EHPA. Under optimal conditions, the extraction process was highly efficient, yielding over 99% yttrium recovery at an optimal pH of 0.75 with a low resin dosage of 0.1 g/L. Furthermore, the solvent-impregnated resins exhibited excellent reusability over five consecutive extraction–stripping cycles, maintaining a single-cycle stripping efficiency above 70% and a cumulative recovery exceeding 97%. This study validates the technical feasibility of an integrated leach–extract–strip process based on impregnated resins as an alternative approach for yttrium recycling from electronic waste, potentially supporting the development of a circular economy.