A comparative state-of-technology review and future directions for rare earth element separation

Opare, Emmanuel Ohene; Struhs, Ethan; Mirkouei, Amin

doi:10.1016/j.rser.2021.110917

Cited by 157 publications

(55 citation statements)

References 93 publications

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“…The rare earth elements (REEs) have been applied to various areas including catalyst, ceramic, phosphor, and alloy due to their unique electronic and magnetic properties. [ 1 ] The global demand for REEs has grown steadily in recent decades owing to their importance in the consumer electronics industry and clean‐energy sector. However, this growing demand for REEs may cause environmental concerns since excessive REEs mining will increase environmental contamination such as soil, water, and plants.…”

Section: Introductionmentioning

confidence: 99%

Repeated Recovery of Rare Earth Elements Using a Highly Selective and Thermo‐Responsive Genetically Encoded Polypeptide

Hussain

Kim

Cho

et al. 2021

Adv Funct Materials

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Rare earth elements (REEs) have become increasingly important materials owing to their use in the high-tech and clean-energy industries. However, the unpredictable supply, possible health risks, and environmentally unsustainable extraction practices associated with REEs have encouraged the development of green technologies for the selective extraction and recovery of metals. This study presents a simple and innovative approach for the selective extraction and recovery of total REEs. Elastin-like polypeptide (ELP) and the REE-binding domain (lanmodulin) are fused to form REEs-sensitive and thermo-responsive genetically encoded ELP called RELP, where ELP offered a reversible, inverse phase transition for repeated uses. The RELP are purified and used for the selective extraction of total REEs from competing non-REEs metals by controlling the solution temperature (4 and 37 °C) and pH. RELP exhibit high REE specificity, even in the presence of non-REE metal ions. The bound REEs are readily recovered during at least six repeated cycles, and the efficiency is maintained. Moreover, REEs are selectively recovered by RELP from steel slag leachate, a potential industrial source of REEs. RELP offers a rapid, selective, and scalable method for REE extraction and recovery. This technology can be adapted to recover other precious metals and commodities.

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Section: Introductionmentioning

confidence: 99%

Repeated Recovery of Rare Earth Elements Using a Highly Selective and Thermo‐Responsive Genetically Encoded Polypeptide

Hussain

Kim

Cho

et al. 2021

Adv Funct Materials

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“…Alternatively, when both solutes have sieving coefficients that fall between 0 and 1, the rectifying configuration enhances the fractionation of the solutes. This approach has utility in emerging precision separations where solutes of similar molecular size and chemistry must be fractionated (e.g., purifying rare earth elements, recovering nutrients from wastewater, , or recycling lithium-ion batteries , ). Notably, when compared to its stripping section counterpart, a rectifying section can offer increased purities at high recoveries.…”

Section: Resultsmentioning

confidence: 99%

Staged Diafiltration Cascades Provide Opportunities to Execute Highly Selective Separations

Kilmartin

Ouimet

Dowling

et al. 2021

Ind. Eng. Chem. Res.

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Improved solute selectivity, an issue commonly approached through the development of advanced membrane materials, can be achieved through staged diafiltration processes. A mathematical model that describes the solute concentration profile within a single diafiltration module is developed and experimentally validated. For this module, where the diafiltrate is introduced uniformly over its length, a critical diafiltrate flux that results in the retentate concentration remaining constant during operations is identified. The model is then extended to examine two configurations of multistage diafiltration cascades: stripping sections and rectifying sections. The two configurations differ based on the connectivity between stages. Namely, stripping sections connect multiple modules by utilizing the retentate from one stage as the feed to the subsequent stage while the permeate is repurposed as the diafiltrate. In contrast, rectifying sections utilize the permeate from one stage as the feed to the subsequent stage and the retentate becomes the diafiltrate. For cascades that operate with a constant diafiltrate to feed flow ratio for all stages, the analysis demonstrates that stripping sections can reduce the diafiltrate consumed when separating low molar mass impurities from larger, impermeable molecules. On the other hand, cascades in a rectifying section configuration can improve the separation of two solutes with finite sieving coefficients between 0 and 1. Finally, asymmetric cascades, i.e., systems in which each stage has a unique diafiltrate to feed flow ratio, are shown to be capable of improving the recovery and purity of solutes in effluent streams relative to systems that operate at constant a diafiltrate to feed ratio. As a whole, the study highlights that the continued advancement of membrane separations will rely equally on thoughtful module and process design as well as the development of new materials.

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“…However, the appropriate pH for the Fe(III) removal by naphthenic acid is 3 in comparison with approximately 2.8 for scandium, which indicates an interference of iron and scandium in the extraction process. An emulsion was formed when iron was completely extracted at a pH of 3.8, leading to a slow phase separation [ 72 ].…”

Section: Separation and Purification Of Rare Earth Elements Using Sxmentioning

confidence: 99%

Scandium Recovery Methods from Mining, Metallurgical Extractive Industries, and Industrial Wastes

et al. 2022

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The recovery of scandium (Sc) from wastes and various resources using solvent extraction (SX) was discussed in detail. Moreover, the metallurgical extractive procedures for Sc recovery were presented. Acidic and neutral organophosphorus (OPCs) extractants are the most extensively used in industrial activities, considering that they provide the highest extraction efficiency of any of the valuable components. Due to the chemical and physical similarities of the rare earth metals, the separation and purification processes of Sc are difficult tasks. Sc has also been extracted from acidic solutions using carboxylic acids, amines, and acidic β-diketone, among other solvents and chemicals. For improving the extraction efficiencies, the development of mixed extractants or synergistic systems for the SX of Sc has been carried out in recent years. Different operational parameters play an important role in the extraction process, such as the type of the aqueous phase and its acidity, the aqueous (A) to organic (O) and solid (S) to liquid (L) phase ratios, as well as the type of the diluents. Sc recovery is now implemented in industrial production using a combination of hydrometallurgical and pyrometallurgical techniques, such as ore pre-treatment, leaching, SX, precipitation, and calcination. The hydrometallurgical methods (acid leaching and SX) were effective for Sc recovery. Furthermore, the OPCs bis(2-ethylhexyl) phosphoric acid (D2EHPA/P204) and tributyl phosphate (TBP) showed interesting potential taking into consideration some co-extracted metals such as Fe(III) and Ti(IV).

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A comparative state-of-technology review and future directions for rare earth element separation

Cited by 157 publications

References 93 publications

Repeated Recovery of Rare Earth Elements Using a Highly Selective and Thermo‐Responsive Genetically Encoded Polypeptide

Repeated Recovery of Rare Earth Elements Using a Highly Selective and Thermo‐Responsive Genetically Encoded Polypeptide

Staged Diafiltration Cascades Provide Opportunities to Execute Highly Selective Separations

Scandium Recovery Methods from Mining, Metallurgical Extractive Industries, and Industrial Wastes

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