The combustion residues derived from coal, lignite, biomass, and spent wash could be recycled to extract critical elements required for energy transition. To recycle these elements from the combustion residues, it is necessary to understand their chemical mode of occurrence in the ash. This study presents the content of critical elements and their chemical mode of occurrence in coal, lignite, biomass, and incinerator ash. Lignite ash, rich in Ca and Si, offers Sc (31 mg/kg) and Nd (212 mg/kg), while coal ash, dominated by Si and Al, contains Ga (44.8 mg/kg). Biomass and spent wash ash, characterized by K, Ca, and S, present substantial potential for potash and Sc. Lignite ash primarily contains rare earth elements (REEs) in metal oxide-bound fractions, whereas in coal ash, the REEs are associated with the hard mullite or quartz phase. Biomass and incinerator ashes have significant water-soluble potash, and the Sc is associated with metal oxides. Green acids can extract critical elements from lignite, biomass, and incinerator ashes, but extracting from coal ash requires harsh conditions. Future research should concentrate on green extraction processes considering the chemical patterns of occurrence of critical elements.

中文翻译：

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回收煤、褐煤和生物质原料燃烧残渣中关键元素的前景


来自煤、褐煤、生物质和废洗涤液的燃烧残留物可以回收利用，以提取能源转型所需的关键元素。要从燃烧残留物中回收这些元素，有必要了解它们在灰烬中出现的化学方式。本研究介绍了煤、褐煤、生物质和焚烧炉灰烬中关键元素的含量及其存在的化学方式。富含 Ca 和 Si 的褐煤灰提供 Sc （31 mg/kg） 和 Nd （212 mg/kg），而以 Si 和 Al 为主的煤灰含有 Ga（44.8 mg/kg）。以 K、Ca 和 S 为特征的生物质和废洗涤灰在钾肥和 Sc 方面具有巨大的潜力。褐煤灰主要在金属氧化物结合馏分中含有稀土元素 （REE），而在煤灰中，REE 与硬莫来石或石英相有关。生物质和焚烧炉灰烬具有重要的水溶性钾，而 Sc 与金属氧化物有关。绿酸可以从褐煤、生物质和焚化炉灰烬中提取关键元素，但从煤灰中提取需要恶劣的条件。未来的研究应集中在考虑关键元素出现的化学模式的绿色提取过程上。