Selective Reduction and Separation of Europium from Mixed Rare-Earth Oxides Recovered from Waste Fluorescent Lamp Phosphors

摘要

Europium is vital to the production of high technology products. In recent years, the worldwide market for europium has been controlled by primary sources in China. However, recycling europium from waste fluorescents is a strategy to supply europium. Waste phosphor powder is recovered from recycled lamps and retorted, sieved, and leached to produce europium and yttrium rich concentrate. Europium is separated from yttrium by reducing Eu(Ⅲ) to Eu(Ⅱ) by selective reduction with zinc and precipitated as europium (Ⅱ) sulfate from solution via sulfuric acid. After building upon previous work and removing unit operations, the optimized conditions for europium sulfate were determined. The effects of varying the entrance pH, quantity of sulfate, choice of inert gas, selective reduction time, and precipitation time were studied upon the final grade and recovery of europium (Ⅱ) sulfate. The final purity of 93.84% of europium (Ⅱ) sulfate with a recovery of 84.2% was obtained after using an entrance pH equal to 2.5, 5 times the stoichiometric ratio of sulfate, a 2 h precipitation time, and 30 min selective reduction time.