University of L'Aquila, Department of Chemistry, Chemical Engineering and Materials - Ex-Optimes Loc., Campo di Pile, 67100 L'Aquila, Italy.
Waste Manag. 2011 Dec;31(12):2559-68. doi: 10.1016/j.wasman.2011.07.004. Epub 2011 Aug 12.
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, 4N H(2)SO(4) 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.
该论文研究了从废弃荧光灯管拆解中回收荧光粉中的钇。在不同的浸出试验中，使用不同的酸（硝酸、盐酸和硫酸）和氨浸出金属。这些测试表明，氨不适合回收钇，而 HNO(3)会产生有毒蒸气。采用全因子设计，用 HCl 和 H(2)SO(4)来评估操作因素的影响。HCl 和 H(2)SO(4)浸出体系在钇提取率方面给出了相似的结果，但后者可以减少钙的提取，随后在下游回收钇化合物时具有优势。在 20% w/v S/L 比、4N H(2)SO(4)浓度和 90°C 的条件下，钇的提取率最大。钇和钙的收率分别接近 85%和 5%。方差分析表明，对于 HCl 和 H(2)SO(4)介质，酸浓度和酸与矿浆密度的相互作用单独对钇的溶解有显著的正影响。根据经验建立了两个模型来估算浸出过程中钇和钙的浓度。沉淀试验表明，至少需要化学计量的草酸才能有效地回收钇，并可以生产出纯的草酸钇 n-水合物（99%级）。如果在设备拆解后回收荧光灯的其他部件（玻璃、黑色和有色金属废料）并加以利用，那么该工艺在经济上是可行的，此外，通常还需要支付给回收公司用于收集、处理或最终处置此类荧光粉的费用。
