Leaching of Rare Earth Elements from End‑of‑Life Fluorescent Lamps Using a Binary Deep Eutectic Solvent: Influential Parameters and Dissolution Mechanism Determination

White fluorescent powder is considered a suitable recycling source for recovery of rare earth elements. In this research, recovery of 8 elements, including Ce, Eu, Gd, La, Lu, Nd, Tb, and Y, from white fluorescent powder was investigated using a binary deep eutectic composed of choline chloride and p-toluene sulfonic acid at a molar ratio of 2:1. Dissolution yields above 95% were observed at 90°C and after 72 h for Eu, Gd, Nd, and Y from a solution concentration of 1 g/L. Data analysis indicated that recovery rates increased significantly as temperature and time rose from 50 to 90°C and from 0–72 h, respectively. Increasing the temperature and duration enhances the probability of effective collisions between sample particles and DES molecules, thereby raising recovery. It was found that the leaching mechanism shifted between the initial 0–3 h window and the subsequent 3–72 h period. Kinetic modeling and activation energy calculations using the Arrhenius equation were applied to Ce, Eu, La, Tb, and Y. Based on the results, the leaching mechanism for the first 3 h of the process was a chemical control model. However, during the 3–72 h period, the kinetic model of Ce and Tb transitioned from a chemical control model to a mixed control model.