A rise in global energy demand has led to an increase in coal consumption. Consequently, global coal fly ash production has increased creating a pressing need for recycling and utilisation of coal fly ash. Since coal fly ash is enriched with rare earth elements one application is to extract rare earth elements from this waste material. There has been a rise in demand for rare earth elements over the past decades due to their use in optics, automotive, electronics, energy, defence industries etc. In this study, a two-stage hydrometallurgical process (alkali fusion-acid leaching) was used to recover rare earth elements from coal fly ash from a South African Power Station (Tutuka Power Station). The coal fly ash was firstly roasted at high temperature with sodium hydroxide, followed by acid leaching with hydrochloric acid. The effect of acid concentration on the recovery of rare earth elements from coal fly ash was investigated. Results indicated that acid concentration had a significant effect on rare earth element recovery. Rare earth element recovery increased as HCl concentration increased from 1 mol/L (0%) to 2 mol/L (33%) and decreased as acid concentration increased to 3 mol/L (29%). Thus, the acid concentration of 2 mol/L was the optimal concentration for rare earth element recovery. In addition, the study showed that the alkali fusion-acid leaching method favoured the recovery of heavy rare earth elements (47.78%) and medium rare earth elements (46.78%) over light rare earth elements (33.93%) due to their mineral associations.

全球能源需求的增加导致煤炭消费量的增加。因此，全球粉煤灰产量增加，迫切需要回收和利用粉煤灰。由于粉煤灰富含稀土元素，因此一种应用是从这种废料中提取稀土元素。在过去的几十年里，由于稀土元素在光学、汽车、电子、能源、国防工业等领域的应用，对稀土元素的需求不断增加。在这项研究中，采用了两阶段湿法冶金工艺（碱熔酸浸出）。用于从南非发电站（图图卡发电站）的粉煤灰中回收稀土元素。粉煤灰先用氢氧化钠高温焙烧，再用盐酸酸浸。研究了酸浓度对从粉煤灰中回收稀土元素的影响。结果表明，酸浓度对稀土元素回收率有显着影响。稀土元素回收率随着 HCl 浓度从 1 mol/L (0%) 增加到 2 mol/L (33%) 而增加，随着酸浓度增加到 3 mol/L (29%) 而降低。因此，2 mol/L 的酸浓度是稀土元素回收的最佳浓度。此外，研究表明，碱熔-酸浸法由于其矿物组合，有利于重稀土元素（47.78%）和中稀土元素（46.78%）的回收率高于轻稀土元素（33.93%）。结果表明，酸浓度对稀土元素回收率有显着影响。稀土元素回收率随着 HCl 浓度从 1 mol/L (0%) 增加到 2 mol/L (33%) 而增加，随着酸浓度增加到 3 mol/L (29%) 而降低。因此，2 mol/L 的酸浓度是稀土元素回收的最佳浓度。此外，研究表明，碱熔-酸浸法由于其矿物组合，有利于重稀土元素（47.78%）和中稀土元素（46.78%）的回收率高于轻稀土元素（33.93%）。结果表明，酸浓度对稀土元素回收率有显着影响。稀土元素回收率随着 HCl 浓度从 1 mol/L (0%) 增加到 2 mol/L (33%) 而增加，随着酸浓度增加到 3 mol/L (29%) 而降低。因此，2 mol/L 的酸浓度是稀土元素回收的最佳浓度。此外，研究表明，碱熔-酸浸法由于其矿物组合，有利于重稀土元素（47.78%）和中稀土元素（46.78%）的回收率高于轻稀土元素（33.93%）。2 mol/L的酸浓度是稀土元素回收的最佳浓度。此外，研究表明，碱熔-酸浸法由于其矿物组合，有利于重稀土元素（47.78%）和中稀土元素（46.78%）的回收率高于轻稀土元素（33.93%）。2 mol/L的酸浓度是稀土元素回收的最佳浓度。此外，研究表明，碱熔-酸浸法由于其矿物组合，有利于重稀土元素（47.78%）和中稀土元素（46.78%）的回收率高于轻稀土元素（33.93%）。