Key Laboratory of Coal Processing & Efficient Utilization, Ministry of Education, School of Chemical Engineering and Technology, China University of Mining & Technology, Xuzhou, 221116, China; Department of Energy and Mineral Engineering, Earth and Mineral Sciences (EMS) Energy Institute, Center for Critical Minerals, The Pennsylvania State University, University Park, 16802, PA, USA.
Key Laboratory of Coal Processing & Efficient Utilization, Ministry of Education, School of Chemical Engineering and Technology, China University of Mining & Technology, Xuzhou, 221116, China.
Chemosphere. 2020 Jun;248:126112. doi: 10.1016/j.chemosphere.2020.126112. Epub 2020 Feb 4.
Coal fly ash (CFA) is one of the most promising secondary sources of rare earth elements and yttrium (REY). This research first studied the modes of occurrence of REY in CFA collected from a China's power generation plant which utilizes a coal feedstock with an elevated REY content. The fact that rare earth minerals remain in CFA and REY associate with metal oxides was proved by emission-scanning electron microscope with an energy-dispersive X-ray spectrometer. The technical feasibility of recovery of REY from CFA was then studied through conducting various physical separation methods followed by acid leaching. It was found that REY are concentrated in fine particle size, non-magnetic and middle density fractions. Using combined physical separation processes, the REY of CFA was enriched from 782 μg·gto 1025 μg g. The acid leaching process was optimized for various parameters via the Taguchi three-level experimental design. Upon optimization, the physical separation product was leached at the optimum condition and 79.85% leaching efficiency was obtained. Based on the obtained results, a conceptual process flowsheet was developed for recovery of REY from CFA. Such recovery maximizes REY resources utilization and enhances sustainability of CFA disposal.
粉煤灰（CFA）是稀土元素和钇（REY）最有前途的二次资源之一。本研究首先研究了从中国某发电厂采集的粉煤灰中 REY 的赋存形态，该发电厂使用的煤料中 REY 含量较高。事实证明，稀土矿物仍存在于粉煤灰中，REY 与金属氧化物有关，这是通过带有能量色散 X 射线光谱仪的发射扫描电子显微镜证明的。然后通过进行各种物理分离方法随后进行酸浸，研究了从粉煤灰中回收 REY 的技术可行性。发现 REY 集中在细颗粒尺寸、非磁性和中等密度馏分中。使用组合的物理分离工艺，将粉煤灰中的 REY 从 782μg·g 富集到 1025μg·g。通过田口三级实验设计对各种参数进行了酸浸工艺优化。优化后，在最佳条件下对物理分离产物进行浸出，获得了 79.85%的浸出效率。基于获得的结果，为从粉煤灰中回收 REY 开发了概念性工艺流程。这种回收最大限度地利用了 REY 资源，增强了粉煤灰处置的可持续性。
