Recovery of Red (Y2O3:Eu³+), Blue(Sr,Ca,Ba)10(PO4)6Cl2:Eu²+ and Green(LaPO4:Tb³+,Ce³+) Rare Earth Phosphors from Waste Phosphor Sludge by Liquid/Liquid Extraction

A new method for recovery of red (Y₂O₃:Eu³⁺), blue (Sr,Ca,Ba)₁₀(PO₄)₆Cl₂:Eu²⁺ and green (LaPO₄:Tb³⁺,Ce³⁺) rare earth phosphors from waste phosphor sludge by liquid/liquid extraction is proposed in this paper. At first ,the recommended pretreatment process is effective to remove the adhesive binder such as Al₂O₃ and the other impurities from the spent florescent powder complex, which including treatment by nitric acid solution of pH 2 for 1-5 minutes, by sodium hydroxide solution of pH 12.5 for 12 minutes and rinsing by 99.5% ethanol and distilled water. The subsequent separation for dried florescent powder was carried out in the heptane/ DMF (N, N-Dimethylformamide) system in presence of DAA (laurylamine) surfactant. Through two steps extraction process with different DAA concentration. Satisfactory separation results have been achieved; the grade and recovery of recovered red, blue and green product reach 86.0% and 80.3%, 74.8% and 95.6%, 81.2% and 79.5%, respectively. This invention provides a new possibility for the recycling of valuable rare earth phosphor from spent fluorescent lamps in the future.