電子廃棄物から重要鉱物を回収(Critical Minerals Recovery from Electronic Waste)

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2024-04-23 パシフィック・ノースウェスト国立研究所(PNNL)

現代生活に不可欠なデバイスである携帯電話やパソコンなどは、古代の産業である鉱業から採掘される鉱物に完全に依存しています。これらが役割を終えると、通常は大量に埋め立てられます。しかし、パシフィックノースウェスト国立研究所の研究チームが開発した方法により、電子廃棄物から貴重な鉱物を回収することが可能になるかもしれません。彼らは、水溶液を用いた単純な方法で、連続的に流れる反応室内で鉱物を分離しました。この研究は、環境にやさしく、スケーラブルな鉱物回収プロセスの開発を目指しており、高価な試薬や時間を要するプロセスを使用せずに、ほぼ純粋な希土類元素を分離・回収することに成功しました。

<関連情報>

水溶液からのネオジムおよびジスプロシウム分離の流れによる促進 Flow-driven enhancement of neodymium and dysprosium separation from aqueous solutions

Qingpu Wang  and  Chinmayee V. Subban
RSC Sustainability  Published:12 Feb 2024
DOI:https://doi.org/10.1039/D3SU00403A

Abstract

Selective extraction of rare earth elements (REEs) from waste NdFeB magnets and natural mineral sources has been challenging due to the similar properties of neodymium (Nd) and dysprosium (Dy). Current separation methods mainly include solvent extraction and organic ligand-based selective precipitation, which are chemical- and energy-intensive in addition to the long separation times required to reach thermodynamic equilibrium. Here, we demonstrate a laminar co-flow method that relies on flow-induced non-equilibrium conditions to selectively precipitate Dy3+ from aqueous solutions containing mixed Nd3+ and Dy3+ at various ratios. The concentration of reactant sodium dibutyl phosphate for selective precipitation was identified based on the differences in the spatiotemporal dynamics of the Nd3+ and Dy3+ precipitates. Under optimized conditions, our method showed increased Dy purity in the precipitate product at significantly shorter reaction times, compared to commonly used convective bulk mixing. We found a nearly Dy-pure (99.9%) precipitate from starting mixtures of Nd : Dy in 50 : 50 and 30 : 70 ratios. Our single-step method is efficient and environmentally friendly and does not require harmful organic solvents or difficult to synthesize complex ligands.

電子廃棄物から重要鉱物を回収(Critical Minerals Recovery from Electronic Waste)

反応拡散カップリングが電池原料水溶液からの金属イオンの逐次析出を促進する Reaction–Diffusion Coupling Facilitates the Sequential Precipitation of Metal Ions from Battery Feedstock Solutions

Qingpu Wang and Elias Nakouzi
Environmental Science & Technology Letters  Published:November 22, 2023
DOI:https://doi.org/10.1021/acs.estlett.3c00754

Abstract

Abstract Image

The development of new technologies for chemical separations is urgently needed to meet the surging demand for critical materials that has strained resources and caused environmental challenges. Inspired by the classic Liesegang experiment, we demonstrated the separation of critical metal ions based on the coupling of ion diffusion and precipitation kinetics. For this purpose, a model feedstock solution simulating dissolved battery electrodes was placed on top of a hydrogel loaded with a precipitating agent, namely, sodium hydroxide. As the lithium, manganese, cobalt, and nickel ions diffused into the gel, a gradient of precipitates formed along the length of the reactor. Elemental analysis of the spatially distributed precipitates showed the enrichment of nickel near the gel–solution interface, followed by the formation of an almost pure (>96%) manganese product further along the reactor. Optimization experiments revealed that a sodium hydroxide concentration of 10 mM and a gel/solution volume ratio of 2:1 favored efficient separations. The robustness of the method was demonstrated in four out of five feedstock compositions of typically used battery cathodes. Our proof-of-concept experiments present a paradigm for critical materials separations that does not require specialty chemicals, binding agents, membranes, or toxic solvents.

0500化学一般
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