High-efficiency simultaneous extraction of rare earth elements and iron from NdFeB waste by oxalic acid leaching

Liu, Qingsheng; Tu, Tao; Guo, Hao; Cheng, Huajin; Wang, Xuezhong

doi:10.1016/j.jre.2020.04.020

Cited by 38 publications

(11 citation statements)

References 34 publications

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“…Surprisingly, for a significant fraction of partially reacted metal-rich particles (∼72%), the transition region held a sharp solid-phase concentration gradient (Figure A2,B2), suggesting that ion diffusion through the leached layer occurred at a rate faster than that of the ion-exchange reaction at the unreacted–leached interface. According to the shrinking core model, ,− outer shell layers completely devoid of products indicate a reaction-controlled process, whereas concentration gradients across the outer leached shell suggest a diffusion-controlled process. The concentration profiles measured in our study, therefore, approximate a reaction-limited process rather than a diffusion-limited process.…”

Section: Resultsmentioning

confidence: 99%

From Ashes to Riches: Microscale Phenomena Controlling Rare Earths Recovery from Coal Fly Ash

Gerardo

Davletshin

Loewy

et al. 2022

Environ. Sci. Technol.

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Coal fly ash is an alternative source of rare earth elements (REEs), which are critical in modern energy and electronic technologies. Current hydrometallurgical processes, however, yield variable recovery rates because of the limited understanding of the microscale phenomena controlling the extraction of REEs from fly ash. This work investigates the microscale processes that dictate the recovery of REEs from ash particulates via a spatiochemical analysis. We find that REE-bearing minerals are hosted in three modes with distinct recovery mechanisms: (i) REEs encapsulated in dense particles are recovered via the cation exchange between matrix metals (Al, Ca, Mg, etc.) and solution cations, (ii) REEs within permeable particles are recovered via intraparticle pore-scale fluid flow, and (iii) discrete and surface-bound REE-bearing minerals are recovered via direct exposure to reagents. The role of metal content and the limiting transport mechanisms are further probed for dense particles, the predominant mode of occurrence. This study highlights, for the first time, how the morphology and the elemental makeup of the ash matrix play a critical role in the accessibility of REEs, furthering the knowledge base required for the design of cost-effective and environmentally benign REEs recovery techniques.

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Section: Resultsmentioning

confidence: 99%

From Ashes to Riches: Microscale Phenomena Controlling Rare Earths Recovery from Coal Fly Ash

Gerardo

Davletshin

Loewy

et al. 2022

Environ. Sci. Technol.

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“…In our previous study on [Hbet][Tf 2 N], we found that iron is a significant contaminant . Moreover, Fe has been described as a dominant contaminant in the literature investigating other extraction methods for REE recovery from CFA, as well as from other REE-containing materials, including NdFeB magnets, ,− acid mine drainage sludge, bauxite mining residues, and ores of monazite, bastnasite, and xenotime. , The ubiquity of Fe across materials and its interesting behavior with [Hbet][Tf 2 N] made it the top priority for optimization.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Iron Removal in the Recovery of Rare-Earth Elements from Coal Fly Ash Using a Recyclable Ionic Liquid

Stoy

Kulkarni

Huang

2022

Environ. Sci. Technol.

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Rare-earth elements (REEs) are essential for modern technologies, and the United States currently lacks a secure domestic supply. Coal combustion residuals, specifically coal fly ash (CFA), can be a potential source. Our previous work demonstrated that REEs could be preferentially extracted from CFA using the ionic liquid (IL) betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]), and the process yielded a mildly acidic REE-rich solution with coextracted Fe and regenerated IL. In this study, we investigated three strategies to limit Fe coextraction: magnetic separation, complexing salts, and ascorbic acid (AA) reduction. Magnetic separation of CFA was ineffective in significantly lowering the Fe content in the IL phase. When NaCl was used instead of NaNO3 during extraction, chloride complexation lowered iron distribution to the IL phase over the aqueous phase (D Fe) by five folds, from ∼75 to ∼14, while REE leaching (L REEs) and recovery (R REEs) both increased. Using AA for iron reduction lowered the overall amount of Fe extracted and further decreased D Fe to ∼0.16, effectively shifting Fe preference from the IL phase to the aqueous phase. Combining the strategies of NaCl, AA, and supplemental betaine addition, leaching and extraction of REEs from CFA by [Hbet][Tf2N] were achieved in higher efficiency for REE recovery with minimized Fe concentration.

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“…Several methods have been developed to recycle REEs from NdFeB magnets. Hydrometallurgical and pyro-hydrometallurgical processes are common methods used to recover REEs from NdFeB wastes, , such as the use of bifunctional ionic liquids as extractants; oxidation roasting combined with hydrochloric acid leaching; nitration, calcination, and water leaching; mechanochemical method combined with ferric sulfate leaching; and roasting and HCl leaching . Electrochemical–hydrometallurgical processes have also been used, such as selective extraction with HCl after electrolysis pretreatment, selective electrochemical extraction with oxalic acid and NaCl, electrolysis and selective precipitation, electrochemical leaching with sulfuric and oxalic acids, and precipitation of REEs in hydrofluoric acid and recycling of Fe by electrodeposition .…”

Section: Introductionmentioning

confidence: 99%

Novel Approach for the Simultaneous Recovery of Nd from Nd₂O₃-Containing Slag and the Preparation of High-Purity Si

Lei

et al. 2021

ACS Sustainable Chem. Eng.

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The extraction of rare earth elements (REEs) from rare earth oxide slag is a major challenge of recycling REEs from REE-containing wastes using pyrometallurgical approaches, especially the recycling of Nd from spent NdFeB permanent magnets. In this study, a novel and effective approach is proposed for extracting Nd from Nd 2 O 3 -containing slag. First, low-purity Si (99.2%) was used as a reductant to extract Nd from Nd 2 O 3containing slag to prepare a bulk Si−Nd alloy. The bulk Si−Nd alloy represents one of the final products and achieves the purpose of Nd recycling because of its wide applications; alternatively, the bulk Si−Nd alloy can be further separated into Si powder and Ndcontaining HCl solution by HCl acid leaching. Thereafter, three methods can be used to recover Nd from the Nd-containing HCl solution: (1) NH 3 •H 2 O can be used to precipitate Nd 3+ as NdOCl hydrate sediment, which is roasted to obtain high-purity NdOCl (99.0%); (2) HF can be used to precipitate Nd 3+ as NdF 3 (97.0%); or (3) NdCl 3 •6H 2 O (98.1%) can be obtained after completely distilling the Nd-containing HCl solution. This new technology not only permits the recovery of Nd from the Nd 2 O 3 -containing slag but also increases the purity of Si from 99.2 to 99.997%.

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High-efficiency simultaneous extraction of rare earth elements and iron from NdFeB waste by oxalic acid leaching

Cited by 38 publications

References 34 publications

From Ashes to Riches: Microscale Phenomena Controlling Rare Earths Recovery from Coal Fly Ash

From Ashes to Riches: Microscale Phenomena Controlling Rare Earths Recovery from Coal Fly Ash

Optimization of Iron Removal in the Recovery of Rare-Earth Elements from Coal Fly Ash Using a Recyclable Ionic Liquid

Novel Approach for the Simultaneous Recovery of Nd from Nd₂O₃-Containing Slag and the Preparation of High-Purity Si

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High-efficiency simultaneous extraction of rare earth elements and iron from NdFeB waste by oxalic acid leaching

Cited by 38 publications

References 34 publications

From Ashes to Riches: Microscale Phenomena Controlling Rare Earths Recovery from Coal Fly Ash

From Ashes to Riches: Microscale Phenomena Controlling Rare Earths Recovery from Coal Fly Ash

Optimization of Iron Removal in the Recovery of Rare-Earth Elements from Coal Fly Ash Using a Recyclable Ionic Liquid

Novel Approach for the Simultaneous Recovery of Nd from Nd2O3-Containing Slag and the Preparation of High-Purity Si

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Novel Approach for the Simultaneous Recovery of Nd from Nd₂O₃-Containing Slag and the Preparation of High-Purity Si