title: Recyclables recovery of europium and yttrium metals and some salts from spent fluorescent lamps.
abstract: 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 1M 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 4h at approximately 125 degrees 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 approximately 80 degrees C. N-tributylphosphate in 1N nitric acid at 125 degrees C achieved a stripping extent of 99%. Thermal reduction using hydrogen gas at 850 degrees C and 1575 degrees 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.
authors.affiliation: Central Metallurgical R&D Institute, Industrial Wastes Laboratory, PO Box 87 Helwan, 11421 Cairo, Egypt. rucmrdi@rusys.eg.net
authors.forename: Mahmoud A
authors.initials: MA
authors.lastname: Rabah
mesh_terms: D003247:Conservation of Natural Resources / Q000191:economics / Q000379:methods*; D005063:Europium / Q000737:chemistry*; D005453:Fluorescence; D008029:Lighting; D013431:Sulfates / Q000737:chemistry; D013861:Thiocyanates / Q000737:chemistry; D015019:Yttrium / Q000737:chemistry*
chemical_list: D013431:Sulfates; D013861:Thiocyanates; D005063:Europium; D015019:Yttrium; C091417:yttria