Characterization techniques and experimental measurements were used to evaluate a process for recycling rare earth elements (REEs) from spent fluorescent lamp phosphors. QEMSCAN analysis revealed that 70% of the rare earth bearing minerals was less than 10 microm in size. Feeds of varying characteristic were received throughout the course of the experimental analysis. A representative sample of the as-received feed contained 5.8% total rare earth elements (TREE) and upon sieving to below 44 microm, the grade increased to 16.5% TREE. By sieving further to below 10 microm, the grade increased to 19.8% TREE. Hydrochloric acid was used as lixiviant in batch leach experiments on the phosphor powder. The maximum extraction obtained was 90% for europium and yttrium at the following conditions: 1.5 M HCl, 70˚C, 1 hr, 30 g/L and 200 rpm. However, the solubility of cerium, lanthanum and terbium remained low under these conditions. Multistage leaching and calcination followed by leaching processes also resulted in poor extraction of cerium, lanthanum and terbium. Based on experimental results a new process for extracting the chief REEs from end of life fluorescent lamps has been developed. The proposed process employs a multistage acid leach using HCl under both mild and strong leaching conditions in addition to thermal treatment of the powder. Using this process, about 90% of the europium and yttrium is extracted in the first stage leach and over 90% of lanthanum in the second stage leach. There is also over 80% of cerium and terbium extracted which marks a significant improvement. Precipitation using oxalic acid as precipitant and sodium hydroxide for pH adjustment was able to recover 100% of the REE from the leach liquor. However, the purity of the mixed rare earth oxides produced is very low because of co-precipitation of impurities from the leach liquor. The process needs to be optimized for potential industrial application.
展开▼
机译：使用表征技术和实验测量来评估回收废荧光灯磷光体中稀土元素（REE）的过程。 QEMSCAN分析显示，含稀土的矿物中有70％的尺寸小于10微米。在整个实验分析过程中，都会收到各种特性的饲料。按原样进料的代表性样品包含5.8％的总稀土元素（TREE），筛分到44微米以下时，品位提高到16.5％TREE。通过进一步筛分至10微米以下，等级提高到19.8％的TREE。在荧光粉粉末的分批浸出实验中，盐酸被用作浸滤剂。在以下条件下，for和钇的最大提取量为90％：1.5 M HCl，70°C，1小时，30 g / L和200 rpm。然而，在这些条件下，铈，镧和ter的溶解度仍然很低。多阶段浸出和煅烧以及随后的浸出过程也导致铈，镧和ter的提取不良。基于实验结果，开发了一种从报废荧光灯中提取主要稀土元素的新方法。所提出的方法除了对粉末进行热处理外，还在温和和强浸条件下采用盐酸进行多级酸浸。使用此过程，在第一阶段浸出中提取约90％的and和钇，在第二阶段浸出中提取超过90％的镧。还提取了80％以上的铈和ter，这标志着显着的改善。用草酸作为沉淀剂和氢氧化钠调节pH值的沉淀能够从浸出液中回收100％的REE。然而，由于从浸出液中杂质的共沉淀，产生的混合稀土氧化物的纯度非常低。该过程需要针对潜在的工业应用进行优化。
展开▼
