Leaching of Rare Earth Metals from Phosphor Coating of Waste Fluorescent Lamps

Phosphors made from compounds of rare earth metals (REMs) are very efficient. This material needs to be recycled for recovery of REMs after the fluorescent lamps (FLs) reach end of life. This work focuses on the leaching studies of REMs from phosphor. The phosphor was recovered from the spent linear FLs by end cut-push method. After detailed characterization of phosphor, effects of parameters viz. leachant, concentration, temperature, and pulp density were studied to determine the optimum leaching conditions. By using 9% (v/v) H2SO4, 98.6% (w/w) yttrium and 96.2% (w/w) europium could be leached out from phosphor at temperature, 70 degrees C, time, 4h, and pulp density, 10% (w/v). The residue generated was treated with 54% (v/v) HCl to leach out 98.9% (w/w) lanthanum, 98.2% (w/w) cerium and 96.5% (w/w) terbium at temperature, 90 degrees C, time, 2h, and pulp density, 10% (w/v). Kinetic studies of leaching reactions were also carried out.