Coordination chemistry of surface-associated ligands for solid–liquid adsorption of rare-earth elements

Hovey, Jessica L.; Dittrich, Timothy M.; Allen, Matthew J.

doi:10.1016/j.jre.2022.05.012

Cited by 25 publications

(8 citation statements)

References 239 publications

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“…A few authors recently reported that coordination chemistry is crucial in segregating REEs [34]. The solid-liquid separation or liquid-liquid separation process involves the use of coordination chemistry.…”

Section: Solution Behavior Of Reesmentioning

confidence: 99%

A Comparative Study on Recent Developments for Individual Rare Earth Elements Separation

2023

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Facilitating the demands of modern society, namely, smartphones, televisions, electric vehicles, and high-stability aircraft structures, requires low-cost and high-performance materials and a corresponding change in the approach needed to design them. Rare earth elements (REEs) play a significant role in achieving these objectives by adding small amounts of these elements to alloys, thereby enhancing material properties. Despite being more abundant than precious metals, the 17 REEs exhibit subtle variations in their chemical and physical characteristics. Thus, their separation is still crucial for industrial applications. There is a corresponding need to develop more effective and efficient separation methods. Adding to the separation challenge is the complexity of the sources of REEs and related materials. Thus, large-scale production of REE materials is difficult. Current REE processing techniques can be categorized into pre-treatment, beneficiation, separation, and refining. Researchers have developed various technologies encompassing chemical, physical, and biological methods, focusing on economic and environmental considerations. However, not all these approaches can be scaled up for mass production. This article focuses on feasible strategies such as precipitation and crystallization, oxidation and reduction, ion exchange, adsorption, solvent extraction, and membrane separation. Further research into these traditional and modern methods can potentially revolutionize the separation dynamics of REEs.

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Section: Solution Behavior Of Reesmentioning

confidence: 99%

A Comparative Study on Recent Developments for Individual Rare Earth Elements Separation

2023

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“…27,28,42,43 Modification of solid supports with ligands is an important technique to separate rare-earth elements based on coordinating angle (bite angle), donor atoms, functional groups, cavity size, range of pK a , or denticity. 24,26,44,45 With increasing specificity of the supported ligand, increased separation efficiencies become possible. Therefore, we hypothesized that 2.2.2-cryptand covalently linked to a solid support would enable the separation of lanthanides from each other as a function of size and charge because 2.2.2-cryptand preferentially binds divalent lanthanides relative to trivalent lanthanides.…”

Section: Introductionmentioning

confidence: 99%

“…Different solid-phase extractants have been studied with respect to their selectivity for rare-earth elements. − Modifications to the solid supports studied for the isolation of rare-earth elements include changing the size of the pores, degree of crosslinking, and degree of functionalization as well as selection of different ligands or functional groups to include on solid supports. ,,, Modification of solid supports with ligands is an important technique to separate rare-earth elements based on coordinating angle (bite angle), donor atoms, functional groups, cavity size, range of p K a , or denticity. ,,, With increasing specificity of the supported ligand, increased separation efficiencies become possible. Therefore, we hypothesized that 2.2.2-cryptand covalently linked to a solid support would enable the separation of lanthanides from each other as a function of size and charge because 2.2.2-cryptand preferentially binds divalent lanthanides relative to trivalent lanthanides .…”

Section: Introductionmentioning

confidence: 99%

Cryptands on a Solid Support for the Separation of Europium from Gadolinium

Kulasekara,

Kajjam,

Praneeth

et al. 2023

ACS Appl. Mater. Interfaces

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With the great demand for europium in green-energy technologies comes the need for innovative methods to isolate the elements. We introduce a solid−liquid extraction method using a 2.2.2-cryptand-modified solid support to separate europium from gadolinium using their differences in electrochemical potential. The method overcomes challenges associated with the separation of those two ions that have similar coordination chemistry in the +3 oxidation state. A competitive adsorption study in the cryptand system between Eu II /Eu III and Gd III shows greater affinity for Eu II relative to Gd III . After separation from Gd III , Eu was released by oxidizing Eu II to Eu III with 99.3% purity. The purity of separated Eu is unaffected by pH between pH 3.0 and 5.5. Overall, we demonstrate that by modifying a solid support with 2.2.2-cryptand, divalent europium can be separated from trivalent gadolinium based on the differences of affinities of 2.2.2cryptand for the two ions.

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“…Another common method for REE extraction is solid–liquid extraction. Solid–liquid extraction of REEs uses a column filled with sorbent media made of solid support that serves as an attachment surface (for example, resin) and functionalized ligands that contain various functional groups for binding REEs (for example, carboxylic acids, phosphoric acids, hydroxamate, and biological ligands). − In such systems, REEs are selectively adsorbed to the column until it is saturated, at which point a stripping solution is applied to elute the REE concentrate. This process offers several advantages relative to solvent extraction, including fast phase separation between the solid adsorbent and REE-bearing solution, reusability, and being organic-solvent-free .…”

Section: Introductionmentioning

confidence: 99%

Recycling Gadolinium from Hospital Effluent via Electrochemical Aerosol Formation

Ranaweera,

Wijesinghe,

Weerarathna

et al. 2023

ACS EST Eng.

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The increasing use of Gd-based contrast agents for magnetic resonance imaging at hospitals and research centers has led to the rapidly growing demand for Gd and Gd anomalies in surface waters. Recycling Gd from hospital effluents could simultaneously address Gd demand and severe concerns about Gd contamination. Here, we present a study relevant to the extraction and preconcentration of Gd from hospital effluents that contain parts per billion-level Gd via the ligand-assisted electrochemical aerosol formation (LEAF) process. We demonstrate that the LEAF process extracts ∼75% Gd III from 50 ppb Gd-spiked water samples, including diluted artificial urine samples while preconcentrating Gd by up to 390-fold. Mechanistic studies confirm that the surface activity of the Gd-binding ligand is essential for successful LEAF extraction. The ligands are recyclable by performing electrophoretic separation in an origami paper device, followed by water extraction. The steep pH gradient and strong electric field in the origami paper device enabled the dissociation of Gd-ligand complexes, spatial separation of Gd and ligand, and precipitation of Gd III as Gd(OH) 3 . Approximately 80% of the ligands were recovered from the paper device by water extraction and reused in subsequent extraction cycles. This straightforward and green method could also be adapted to other aqueous rare earth metal wastes in the future.

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Coordination chemistry of surface-associated ligands for solid–liquid adsorption of rare-earth elements

Cited by 25 publications

References 239 publications

A Comparative Study on Recent Developments for Individual Rare Earth Elements Separation

A Comparative Study on Recent Developments for Individual Rare Earth Elements Separation

Cryptands on a Solid Support for the Separation of Europium from Gadolinium

Recycling Gadolinium from Hospital Effluent via Electrochemical Aerosol Formation

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