Rabah Mahmoud A
Central Metallurgical R&D Institute, Industrial Wastes Laboratory, PO Box 87 Helwan, 11421 Cairo, Egypt.
Waste Manag. 2008;28(2):318-25. doi: 10.1016/j.wasman.2007.02.006. Epub 2007 Jun 12.
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.
从荧光灯玻璃管内表面的粉末涂层中回收了铕和钇金属以及一些有价值的盐。将灯管在30%的丙酮水溶液中破碎，以避免汞蒸气排放到大气中，然后通过刷洗收集粉末。粉末中的金属用硫酸/硝酸混合物进行加压浸出。如此得到的铕和钇的硫酸盐转化为硫氰酸盐。使用三甲基苄基氯化铵溶剂从硫氰酸盐溶液中选择性萃取铕和钇。负载在有机溶剂中的金属通过磷酸三丁酯在1M硝酸中进行反萃取，以生产铕和钇的硝酸盐。硝酸铕通过溶解在乙醇中与硝酸钇分离。分离出的粉末按重量计含有氧化铕1.62%、氧化钇1.65%、硫酸钙34.48%、正磷酸钙61.52%和其他杂质金属0.65%。将粉末在酸混合物中于约125℃和5MPa下进行高压釜消化4小时，溶解了96.4%的钇和92.8%的铕。硫酸盐向硫氰酸盐的转化在低温下更有利。从硫氰酸盐溶液中萃取铕和钇在约80℃时达到最大值。磷酸三丁酯在1N硝酸中于125℃时反萃取率达到99%。分别在850℃和1575℃下用氢气进行热还原生成了铕和钇金属。实现了9.4的金属分离系数。经济评估表明，所建议的方法在工业应用中似乎是可行的。
