Recycle Rare Earth from Wastephosphor by a Two-Step Method

Abstract

In this paper, a new two acid hydrolysis (TAH) method has been studied for leaching rare earth (RE) from waste rare earth tricolor phosphor powders collected from spent fluorescent lamps and cathode ray tubes. Firstly, red phosphor powders (Y2O3: Eu) were dissolved by hydrochloric acid. Blue phosphor powders (Ba0.9Mg2Al16O27:0.1Eu) and Green phosphor powders (MgAl11O19: Ce, Tb) of the waste powder could not be dissolved by acid, which is named as “residue 1”, Leaching rate of yttrium and europium were 96.767% and 93.686%, respectively. Secondly, the residue 1 was decomposed into the mixture of NaAlO2, MgO, BaCO3 and Rare Earth Oxide (REO) by alkali fusion at 800°C for 2 hours. The mixture was separated into NaAlO2 solution and residue 2 containing REO by water-washing and filtrating. Finally, residue 2 was dissolved by hydrochloric acid. The total RE (TRE) leaching rate was 97.87% and the leaching rates of yttrium, europium, terbium and cerium after two acid hydrolysis were 98.405%, 99.02%, 98.45% and 96.16%, respectively. Ca2+, Mg2+ and Ba2+, were removed by adding Na2SO4. Compared to traditional method, one acid hydrolysis (OAH), TAH method could decrease the consumption of caustic soda, which is only 1/3~1/2, and reduce the burden of later RE extraction, separation and purification.