2023-03-24 ワシントン大学セントルイス校
この研究で開発された抽出プロセスは、炭酸ガス、窒素、空気などの一般的な超臨界流体を使用し、廃棄物になる石炭フライアッシュからREEを回収するもので、年間生成される79百万トン以上の石炭飛灰から抽出できるREEの潜在的な価値は、年間40億ドル以上に上るという。環境に配慮した方法であり、廃棄物の削減と改善のための手段となると、研究者たちは述べている。
＜関連情報＞
- https://source.wustl.edu/2023/03/novel-process-extracts-rare-earth-elements-from-waste/
- https://engineering.wustl.edu/news/2023/Novel-process-extracts-rare-earth-elements-from-waste.html
- https://pubs.rsc.org/en/content/articlelanding/2023/SU/D2SU00033D
多段ストリッピングによる超臨界二酸化炭素/窒素/空気抽出で石炭飛灰から希土類元素の選択的な回収が可能に Supercritical carbon dioxide/nitrogen/air extraction with multistage stripping enables selective recovery of rare earth elements from coal fly ashes
Yaguang Zhu, Guangcheng Wang§ and Young-Shin Jun
RSC Sustainability Published:16 Jan 2023
DOI:https://doi.org/10.1039/D2SU00033D
Abstract
Rare earth elements (REEs) are widely used in electronic devices and renewable energy technology, but their supply is geopolitically-limited and they are extracted by environmentally unsustainable mining practices. Coal fly ash (CFA), which is mostly discarded as waste, has recently gained attention as a potential low-grade REE source, motivating the development of greener and highly specific processes for recovering and enriching REEs. Here we present a proof-of-concept for a novel REE extraction process in which supercritical fluid enhances the ability of tributyl phosphate (TBP) to selectively extract REEs directly from solid CFA matrices. For the first time, we show that supercritical nitrogen and supercritical air can work like supercritical carbon dioxide for selective extraction. Moreover, using a prototype multistage stripping process with an aqueous solution, we collected REEs with concentrations up to 21.4 mg L−1 from the extractant. Our final products contain up to 6.47% REEs, whereas the coal fly ash source initially contained only 0.0234% REEs. Using supercritical fluid, our novel process can recover valuable and critical resources from materials previously considered to be waste.
