Recovery of an yttrium europium oxide phosphor from waste fluorescent tubes using a BrOnsted acidic ionic liquid, 1-methylimidazolium hydrogen sulfate

BACKGROUNDSpent fluorescent lamps, classified as hazardous waste in the EU, are segregated at source. Processes for the recovery of critical rare-earth (RE) elements from the phosphor powder waste, however, often involve use of aggressive acid or alkali digestion, multi-stage separation procedures, and production of large aqueous waste streams which require further treatment. RESULTSTo overcome these difficulties phosphor powder pre-treated with dilute HCl was leached with a 1:1 wt. [Hmim][HSO4]:H2O solution at a solid:liquid ratio of 5%, at 80 degrees C for 4h with stirring at 300rpm to recover 91.6wt% of the Y and 97.7wt% of the Eu present. The yttrium-europium oxide (YOX), (Y0.95Eu0.05)(2)O-3, recovered by precipitating the dissolved RE elements from the leach solution with oxalic acid and converting the oxalate to an oxide phase by heating, was characterised by FTIR, XRD and luminescence analysis. The analyses suggest the recovered oxide has the potential to be directly reused as YOX phosphor. Regeneration and reuse of the ionic liquid is achieved with only minor leaching efficiency losses found over four leaching/recovery cycles. CONCLUSIONThe recovery of yttrium europium oxide from waste fluorescent tube phosphor by a simple efficient low cost ionic liquid process has been developed. (c) 2017 Society of Chemical Industry