Zheng Yanmin, Zhao Lei, French David, Graham Ian, Wei Qiang, Dai Shifeng, Feng Lili
College of Geoscience and Survey Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China.
College of Geoscience and Survey Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China.
Sci Total Environ. 2024 Nov 10;950:175056. doi: 10.1016/j.scitotenv.2024.175056. Epub 2024 Jul 31.
Coal fly ash has gained much attention as a potential alternative source for extracting critical metals such as Li, Ga, Nb, and lanthanides and yttrium (REY). This study investigates their distribution characteristics and modes of occurrence in alumina-rich fly ashes from the Togtoh Power Plant in Inner Mongolia, using various analytical methods. The objective was to provide a reference for the pre-enrichment of critical metals in fly ash. Lithium is primarily present in the glass phase, and its concentration is extremely low in the crystalline phases. Lithium is mainly concentrated in "pure" aluminosilicate glass, and is present but at a low level in Ca-rich aluminosilicate glass. Gallium is primarily present in the glass phase and in corundum, while Nb mainly exists in submicron zircon particles surrounded by Si-Al-Ca glass. Lanthanides and yttrium primarily occur in the glass phase and in crystalline phases, including an intermediate phase composed of the three end-member minerals of the gorceixite-crandallite-florencite series, as well as in monazite, crystalline forms of iron oxides and REY oxides. The Li concentrations in the alumina-rich fly ashes range from 562 to 894 μg/g for LiO, from 43.9 to 81.9 μg/g for Ga, from 58.7 to 70.6 μg/g for NbO, and from 258 to 450 μg/g for REY oxides, respectively, indicating their substantial potential for resource recovery. Especially, the 2nd row fly ash has the highest contents of these metals, allowing for direct extraction without the necessity for complex pre-processing. Physical separation can further enrich Li, Ga, Nb, and REY in the fly ash. In particular, particle size separation enriches these elements in the < 20 μm size range and magnetic separation enriches Li, Ga, Nb, and REY (except Ce) in the non-magnetic fraction. However, Ce is significantly enriched in the magnetic fraction compared to the original fly ash.
作为一种潜在的替代来源，用于提取锂、镓、铌以及镧系元素和钇（稀土元素）等关键金属，粉煤灰已备受关注。本研究采用多种分析方法，调查了内蒙古托克托电厂富铝粉煤灰中这些关键金属的分布特征和赋存形态。目的是为粉煤灰中关键金属的预富集提供参考。锂主要存在于玻璃相中，在结晶相中其浓度极低。锂主要集中在“纯”铝硅酸盐玻璃中，在富钙铝硅酸盐玻璃中也有存在但含量较低。镓主要存在于玻璃相和刚玉中，而铌主要存在于被硅 - 铝 - 钙玻璃包围的亚微米级锆颗粒中。镧系元素和钇主要存在于玻璃相和结晶相中，包括由磷钇矿 - 磷铝石 - 氟铈矿系列的三种端元矿物组成的中间相，以及独居石、铁氧化物的晶体形式和稀土元素氧化物。富铝粉煤灰中氧化锂的锂浓度范围为562至894μg/g，镓为43.9至81.9μg/g，氧化铌为58.7至70.6μg/g，稀土元素氧化物为258至450μg/g，这表明它们具有可观的资源回收潜力。特别是，第二排粉煤灰中这些金属的含量最高，无需复杂的预处理即可直接提取。物理分离可进一步富集粉煤灰中的锂、镓、铌和稀土元素。具体而言，粒度分离可在<20μm粒径范围内富集这些元素，磁选可在非磁性部分富集锂、镓、铌和稀土元素（铈除外）。然而，与原始粉煤灰相比，铈在磁性部分显著富集。
