Recyclables recovery of europium and yttrium metals and some salts from spent fluorescent lamps

Europium and yttrium metals and some valuable salts were recovered from the powder coating the inner surface of the glass tubes of fluorescent lamps. The tubes were broken under 30% aqueous acetone to avoid emission of mercury vapor to the atmosphere, and the powder was collected by brushing. Metals available in the powder were pressure leached using sulfuric/nitric acid mixture. Sulphate salt of europium and yttrium so obtained was converted to thiocyanate. Trimethyl-benzylammonium chloride solvent was used to selectively extract Eu and Y from the thiocyanate solution. The metal loaded in the organic solvent was recovered by N-tributylphosphate in 1 M nitric acid to produce nitrate salts of Eu and Y. Europium nitrate was separated from yttrium nitrate by dissolving in ethyl alcohol.The isolated powder contained 1.62% europium oxide, 1.65% yttrium oxide, 34.48% calcium sulphate, 61.52% Ca orthophosphate and 0.65% other impurity metals by weight. Autoclave digestion of the powder in the acid mixture for 4 h at ≈125 °C and 5 MPa dissolved 96.4% of the yttrium and 92.8% of the europium. Conversion of the sulphate to thiocyanate is favoured at low temperature. Extraction of Eu and Y from the thiocyanate solution attained its maximum at ≈80 °C. N-tributylphosphate in 1 N nitric acid at 125 °C achieved a stripping extent of 99%. Thermal reduction using hydrogen gas at 850 °C and 1575 °C produced europium and yttrium metals, respectively. A metal separation factor of 9.4 was achieved. Economic estimation revealed that the suggested method seemed feasible for industrial applications.