Coal fly ash (CFA), an anthropogenic waste generated from the combustion of coal, is in research focus for the potential it holds in extracting critical metals. Within the classification of critical metals, includes a group of 16 commercially significant metals known as rare earth elements (REEs). The supply of REEs is touted as one of the building blocks of the 21st century to realize a sustainable future. High demand projections for the future coupled with market monopolization, provide an impetus to extract REEs from secondary resources such as CFA. In this study, three Victorian brown CFA samples were examined, quantifying 41 metals and 16 REEs. All three CFA samples had an outlook coefficient (i.e., ratio of the relative amount of critical REE to the relative amount of excess REE) > 0.7, with an observed light REE enrichment and Eu anomaly, implicating the samples as a suitable feedstock for REE extraction. Quantification studies rendered Loy Yang CFA, from the largest power station in Australia, to be rich with REEs with a total metal concentration of 418 mg/kg, followed by CFA from other power stations (Yallourn: 73.6 mg/kg and Morwell: 36.1 mg/kg). A comparative study for different methods of calibration during inductively coupled plasma - mass spectrometry analysis (and external vs internal calibration), depicted the reproducible nature of results while using an internal standard. Subsequently an in-house developed multi-element standard addition method is proposed, within an accuracy of 2–50 %. A new sequential extraction method for studying modes of occurrences in CFA, depicting REE association with larger fractionation, is explored, with results rendering REE association with: aluminosilicate bound (∼ 61.2 %) > acid soluble fraction (23.1 %) > crystalline Fe bound (5.9 %) > organic matter bound (5.3 %) > amorphous Fe bound (3.5 % TREE) > Mn-oxide bound (0.9 % TREE) > water soluble mineral bound (0.1 % TREE). This underpins the strong REE association in the residual and acid soluble fraction in brown CFA.

中文翻译：

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维多利亚褐煤粉煤灰中关键金属和稀土元素的定量和回收前景：一种有前途的关键金属提取辅助来源


粉煤灰 （CFA） 是煤炭燃烧产生的人为废物，因其在提取关键金属方面的潜力而成为研究重点。在关键金属分类中，包括一组 16 种具有商业意义的金属，称为稀土元素 （REE）。稀土元素的供应被吹捧为 21 世纪实现可持续未来的基石之一。对未来的高需求预测加上市场垄断，为从 CFA 等二级资源中提取 REE 提供了动力。在这项研究中，检查了三个维多利亚棕色 CFA 样品，量化了 41 种金属和 16 种稀土元素。所有三个 CFA 样品的前景系数（即临界 REE 的相对量与过量 REE 的相对量之比）> 0.7，观察到轻度 REE 富集和 Eu 异常，表明样品是 REE 提取的合适原料。定量研究表明，来自澳大利亚最大发电厂的 Loy Yang CFA 富含稀土元素，总金属浓度为 418 mg/kg，其次是来自其他发电厂的 CFA（Yallourn：73.6 mg/kg 和 Morwell：36.1 mg/kg）。在电感耦合等离子体-质谱分析（以及外部校准与内部校准）期间，对不同校准方法的比较研究描述了使用内标时结果的可重现性。随后，提出了一种内部开发的多元素标准添加方法，准确度为 2–50 %。探索了一种新的顺序提取方法，用于研究 CFA 中出现的模式，描述了 REE 与较大分馏的关联，结果使 REE 与以下相关：铝硅酸盐结合 （∼ 61.2 %） > 酸溶性馏分 （23.1 %） > 结晶 Fe 结合 （5.9 %） > 有机物结合 （5.3 %） > 无定形 Fe 结合 （3.5 % TREE） > 氧化锰结合 （0.9 % TREE） > 水溶性矿物结合 （0.1 % TREE）。这支持了棕色 CFA 中残留和酸溶性部分的强烈 REE 关联。