Treatment of exhaust fluorescent lamps to recover yttrium: Experimental and process analyses

被引:119
作者
De Michelis, Ida [1 ]
Ferella, Francesco [1 ]
Varelli, Ennio Fioravante [1 ]
Veglio, Francesco [1 ]
机构
[1] Univ Aquila, Dept Chem Chem Engn & Mat Ex Optimes Loc, I-67100 Laquila, Italy
关键词
Fluorescent; Lamp; Yttrium; Rare earths; WEEE; RARE-EARTH; EXTRACTION; LANTHANUM;
D O I
10.1016/j.wasman.2011.07.004
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
The paper deals with recovery of yttrium from fluorescent powder coming from dismantling of spent fluorescent tubes. Metals are leached by using different acids (nitric, hydrochloric and sulphuric) and ammonia in different leaching tests. These tests show that ammonia is not suitable to recover yttrium, whereas HNO(3) produces toxic vapours. A full factorial design is carried out with HCl and H(2)SO(4) to evaluate the influence of operating factors. HCl and H(2)SO(4) leaching systems give similar results in terms of yttrium extraction yield, but the last one allows to reduce calcium extraction with subsequent advantage during recovery of yttrium compounds in the downstream. The greatest extraction of yttrium is obtained by 20% w/v S/L ratio, 4 N H2SO4 concentration and 90 C. Yttrium and calcium yields are nearly 85% and 5%, respectively. The analysis of variance shows that acid concentration alone and interaction between acid and pulp density have a significant positive effect on yttrium solubilization for both HCl and H(2)SO(4) medium. Two models are empirically developed to estimate yttrium and calcium concentration during leaching. Precipitation tests demonstrate that at least the stoichiometric amount of oxalic acid is necessary to recover yttrium efficiently and a pure yttrium oxalate n-hydrate can be produced (99% grade). The process is economically feasible if other components of the fluorescent lamps (glass, ferrous and non-ferrous scraps) are recovered after the equipment dismantling and valorized, besides the cost that is usually paid to recycling companies for collection, treatment or final disposal of such fluorescent powders. (C) 2011 Elsevier Ltd. All rights reserved.
引用
收藏
页码:2559 / 2568
页数:10
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