Recovery of rare earth elements from CRT phosphors Par 2026 Separation and

Rare earth elements (REEs) are critical raw materials with unique physical-chemical properties, being widely used in phosphors for lighting devices, including CRT screens. These are now being stockpiled, and greener recovery routes are needed to reintroduce REEs into the market for proper valorisation. This work (part one of a two-paper set) evaluates phosphor sieving and acid leaching to select optimal fractions and elucidate leaching kinetics. Phosphors were characterized by XRD, PIXE and SEM-EDS. Sieving effectively removed contaminants (Al, Si, Sr, Ba, Pb). The < 38 μm fraction is enriched in ZnS and Y2O2S; XRD, PIXE, XRF, ICP-OES and SEM-EDS showed Zn, S and Y as main elements. ZnS and (Y0.9597Eu0.0403)2O2S appear as angular or modular particles without clear phase distinction. For this fraction, mass density was 2.41 g/cm3 and humidity 0.1912%. Acid leaching with 3 M HNO3 plus 6 g H2O2/g sulphur was tested at 25, 40 and 55 °C to track Y, Eu and Zn leaching profiles. Higher temperatures enhanced Y, Eu and Zn leaching recoveries and rates, while 25 °C improved REE selectivity from Zn. Recoveries were fit into shrinking-core and shrinking-particle models. At lower temperature, leaching rates are reaction-controlled; at higher temperatures, diffusion becomes significant, particularly for Zn. SEM-EDS revealed alpha-sulphur deposition on unreacted cores, introducing diffusion limitations at higher temperature. The apparent activation energy for Zn leaching was much higher than for REEs, explaining slower Zn release. Differences likely stem from transition state enthalpy and crystal structure rather than lattice energy.