Separation Of Lanthanides Research Articles

Glycopolymer-Mediated Selective Separation of Middle Rare Earth Elements.

The selective separation of rare earth elements (REEs), particularly middle REEs (MREEs) with intermediate ionic radii, poses significant challenges for current methods. In this study, we introduce a novel approach that leverages negatively charged glycopolymers for size-specific separation of MREEs. By varying glycopolymer properties such as degree of polymerization (DP) and charge density, we achieved a distinct U-shaped selectivity profile, with a pronounced preference for Samarium (Sm) and Europium (Eu) over other REEs like Cerium (Ce), Gadolinium (Gd), and Holmium (Ho). Enrichment experiments demonstrated the practical potential of this methodology, achieving over 10% selectivity for Sm in Ce/Sm and Ho/Sm mixtures (10:1 ratios). Further, a separation experiment with a 1:1 Ce/Sm mixture yielded 15% enrichment after five filtration cycles with minimal glycopolymer, underscoring the approach's effectiveness. This work highlights the promise of glycopolymer-based strategies for targeted MREE separation, offering an efficient and tunable pathway for refining separation processes in REE applications.

Glycopolymer‐Mediated Selective Separation of Middle Rare Earth Elements

The selective separation of rare earth elements (REEs), particularly middle REEs (MREEs) with intermediate ionic radii, poses significant challenges for current methods. In this study, we introduce a novel approach that leverages negatively charged glycopolymers for size‐specific separation of MREEs. By varying glycopolymer properties such as degree of polymerization (DP) and charge density, we achieved a distinct U‐shaped selectivity profile, with a pronounced preference for Samarium (Sm) and Europium (Eu) over other REEs like Cerium (Ce), Gadolinium (Gd), and Holmium (Ho). Enrichment experiments demonstrated the practical potential of this methodology, achieving over 10% selectivity for Sm in Ce/Sm and Ho/Sm mixtures (10:1 ratios). Further, a separation experiment with a 1:1 Ce/Sm mixture yielded 15% enrichment after five filtration cycles with minimal glycopolymer, underscoring the approach's effectiveness. This work highlights the promise of glycopolymer‐based strategies for targeted MREE separation, offering an efficient and tunable pathway for refining separation processes in REE applications.

Selective Extraction of Terbium Using Functionalized Metal–Organic Framework-Based Solvent-Impregnated Mixed-Matrix Membranes

Advancements in membrane separation techniques will expand the applications and requirements for highly specialized, inventive, efficient, and resistant separation materials. The selective separation of rare earth elements (REEs) is one of the expanding applications of membrane-based techniques, as their use is becoming more widespread. Membrane techniques are becoming increasingly desired as environmentally friendly, straightforward methods for treating wastewater and separating metals. For the separation of REEs, an innovative impregnated mixed-matrix membrane (IMMM) technique was developed in this study. It provides a selective, efficient, and reusable method that is suitable for industrial applications. Terbium was selectively adsorbed from other REEs using organophosphorus IMMM with a loading capacity of 113.2 mg/g in 3 h and was reused three times without destroying the initial membrane. Solvent impregnation is thought to offer specific chelation sites that are selective for terbium separation.

Research on the Hierarchical Separation of Rare Earths and Lithium from Rare Earth Molten Salt Slag

Lithium is an important non-renewable resource, and the study of the tiered separation of rare earths and lithium from rare earth molten salt slag is an important approach to solving the current global resource shortage. This article adopts a sulfuric acid leaching process and a lithium-containing solution iron lithium extraction separation process to recover lithium from rare earth molten salt slag. The method systematically investigates the impact of sulfuric acid concentration, liquid-to-solid ratio, leaching temperature, leaching time, pH, P507 concentration, phase ratio, extraction temperature, and extraction time on the lithium extraction effect and iron lithium separation effect in rare earth molten salt slag. The results show that under the conditions of a sulfuric acid concentration of 0.9 mol/L, a liquid-to-solid ratio of 8:1 mL/g, a leaching temperature of 70 °C, a leaching time of 90 min, a pH of 0.9, a P507 concentration of 50%, a phase ratio of 5:3, an extraction temperature of 30 °C, and an extraction time of 20 min, the lithium leaching rate reaches 97.8%, and the separation of iron and lithium is fully achieved. This method can efficiently recover the valuable element lithium from rare earth molten salt slag, which is of great significance for the subsequent preparation of lithium products and the realization of a closed-loop production of rare earth alloys by molten salt electrolysis.

Selective Growth of Nb-Fe-B Intermetallic Compounds for the Direct Separation of Rare Earths Based on Manipulating Liquation

Since the primary goal of industrialization has changed to carbon neutrality, the importance of rare earths (REs) has increased due to their criticality in green industries. The attainment of sustainable resources via green production processes is necessary due to the increasing need for REs. Liquid metal extraction is regarded as a leading technology for supporting the sustainability of resources based on the selective reactivity between REs and extractants. However, this process requires multiple stages, including pretreatment, extraction and separation, which are considered bottlenecks in industrialization. In this work, reverse selectivity is applied instead of conventional liquid metal extraction (c-LME) for the direct separation of REs in a single stage. Niobium (Nb) is selected because of its thermodynamic properties for enhancing the selectivity of the reactions between the extractant and other elements, excluding REs. The process is thermodynamically designed for liquation systems, and it reflects the interactions between the extractant and magnets. The solidification behavior based on the selective growth of phases without REs is shown with variations in the composition and cooling rate to confirm the kinetics. The composition prevents the formation of RE-Fe intermetallic compounds, and excess Nb is considered a bottleneck for separating REs. In addition, the cooling rate influences the agglomeration of RE as a layer. Because of the manipulation of the liquation, 92.89% of the REs are successfully separated in the form of accumulated layers. This effective process for the direct separation of REs is verified through thermodynamic and experimental assessments. Overall, this investigation can provide new guidelines for the construction of a circular economy after improving the energy efficiency of this system in future research.

Modulating metal-centered dimerization of a lanthanide chaperone protein for separation of light lanthanides

Elucidating details of biology's selective uptake and trafficking of rare earth elements, particularly the lanthanides, has the potential to inspire sustainable biomolecular separations of these essential metals for myriad modern technologies. Here, we biochemically and structurally characterize Methylobacterium (Methylorubrum) extorquens LanD, a periplasmic protein from a bacterial gene cluster for lanthanide uptake. This protein provides only four ligands at its surface-exposed lanthanide-binding site, allowing for metal-centered protein dimerization that favors the largest lanthanide, LaIII. However, the monomer prefers NdIII and SmIII, which are disfavored lanthanides for cellular utilization. Structure-guided mutagenesis of a metal-ligand and an outer-sphere residue weakens metal binding to the LanD monomer and enhances dimerization for PrIII and NdIII by 100-fold. Selective dimerization enriches high-value PrIII and NdIII relative to low-value LaIII and CeIII in an all-aqueous process, achieving higher separation factors than lanmodulins and comparable or better separation factors than common industrial extractants. Finally, we show that LanD interacts with lanmodulin (LanM), a previously characterized periplasmic protein that shares LanD's preference for NdIII and SmIII. Our results suggest that LanD's unusual metal-binding site transfers less-desirable lanthanides to LanM to siphon them away from the pathway for cytosolic import. The properties of LanD show how relatively weak chelators can achieve high selectivity, and they form the basis for the design of protein dimers for separation of adjacent lanthanide pairs and other metal ions.

Structural and Thermodynamic Analyses of the Complexation of Pr(III), Nd(III), and Eu(III) with Lactate for Simulating the TALSPEAK Process.

The complexation of Pr(III), Nd(III), and Eu(III) with lactic acid/lactate (HA/A-) in aqueous solution was reinvestigated using spectroscopic and potentiometric titrations. In addition to the well-confirmed 1:1, 1:2, and 1:3 complexes (LnA2+, LnA2 +, and LnA3), more attention was given to the arguable 1:4 species (LnA4 -) previously reported. With spectroscopic methods, the LnA4 - species was clearly identified in aqueous solutions, and the capability and limitation of the potentiometric method were evaluated and discussed. With the confirmed stability constants for the four complexes, a simulation of the TALSPEAK process (Trivalent Actinide Lanthanide Separation with Phosphorus-Reagent Extraction from Aqueous Complexes) was performed, clarifying the error caused by the previously missing 1:4 species. It was found that high concentrations of lactic acid/lactate (over 2 mol/L) slightly affect the extraction of Ln(III) in the TALSPEAK process, but it might not be accountable for the considerable difference between experimental results and predictions from the simulation using currently adapted model.

Microalgae for the Extraction and Separation of Rare Earths: An STXM Study of Ce, Gd, and P

Microalgae for the Extraction and Separation of Rare Earths: An STXM Study of Ce, Gd, and P

A novel extraction process for efficient recovery of rare earth elements from the leaching liquor of ion-adsorption type rare earth ore using unsaponified N, N-di(2-ethylhexyl)-diglycolamic acid

There are still challenges in the recovery of rare earth elements (REEs) from leaching liquor of ion-adsorption type rare earth ore. In this paper, unsaponified N, N-di(2-ethylhexyl)-diglycolamic acid (HDEHDGA) was used to develop a green extraction process for efficient separation and enrichment of REEs. The cation exchange mechanism of RE(III) extraction was proposed by slope analysis and FT-IR spectra. HDEHDGA exhibited excellent extraction performances, such as short equilibrium time, high selectivity towards RE(III) and easy stripping by 0.5 mol/L HCl solution. REEs was enriched from 287.5 mg/L to 63.30 g/L by five-stage counter-current extraction and three-stage counter-current stripping using unsaponified HDEHDGA. The enrichment factor reached 220, and the proportion of REEs was increased from 80.76 wt% to 98.82 %. The loss of REEs was controlled below 2.14 wt%. This extraction strategy helps to improve the REEs recovery and avoid ammonia–nitrogen wastewater, which demonstrates its application potential in the ion-adsorption type rare earth ore.

Construction of Ion-Imprinted Graphene Oxide Mixed-Matrix Membranes for Selective Adsorption and Separation of Tm3.

Efficient adsorption and separation of rare earth from other similar rare earth wastewater has become an urgent demand for resource utilization of ion-type rare earth minerals in China. Herein, thulium (Tm) ion-imprinted graphene oxide (GO)-doped polyether sulfone (PES) membranes (GO-TII/PES-2 membranes) were prepared, in which ion-imprinted graphene oxide was applied as an efficient Tm3+ ionic ligand in the imprinted layer and polyether sulfone was applied as a carrier in the membrane matrix to achieve the selective adsorption and separation of Tm3+ and neighboring rare earth ions. Combined with an ion rectifier, the separation and purification performances of Tm3+ were explored. The separation factors β(Tm3+/Tb3+), β(Tm3+/Sm3+), β(Tm3+/Nd3+), and β(Tm3+/Ce3+) in the dynamic adsorption process increased significantly from 1.22, 1.04, 1.04, and 1.02 for nonimprinting to 3.07, 3.91, 3.91, and 3.33 for imprinted membranes. The GO-TII/PES-2 membrane adsorbed about three times more Tm3+ than the nonionic-imprinted (GO-NII/PES) membrane by adding a color developer and quantifying Tm3+ based on a fast and easy UV-photometric method. After eight dynamic permeations, the adsorption of Tm3+ by the GO-TII/PES-2 membrane decreased by only 13%, indicating that the membrane has good reuse performance. Additionally, the investigation examined the influence of Tm3+ on wheat seed germination, underscoring its potential application in agriculture and the importance of adsorbing and separating rare earth ions.

Preparation of large specific surface rare earth oxides from calcium-containing rare earth solution by carbon dioxide carbonization method☆

The calcium-containing rare earth solution is generated during the recovery processes of NdFeB waste, which is treated as wastewater by enterprises. In this paper, the carbon dioxide carbonization method was applied to the separation of rare earths and calcium in the solution, as well as the preparation of rare earth oxides with a large specific surface. It is shown that the process of CO2 carbonization of solution includes reactions such as the dissolution, diffusion and ionization of CO2, the carbonate precipitation of rare earth ions, and the neutralization of hydrogen ions. At a pH of 4.5, the carbonization precipitation rate is effectively controlled, enabling homogeneous precipitation and ensuring both high precipitation yield and rare earth oxides purity. In this way, the crystallization of carbonization products is a process dominated by the oriented attachment theory and coexisting with the Ostwald ripening theory, resulting in abundant pores formed by multiple layers of stacking in the products. With the optimal carbonization conditions, the rare earth precipitation yield solution reaches 99.32%. The obtained carbonization products are crystalline (LaCe)(CO3)3·8H2O, and the purity of the rare earth oxides is as high as 99.22 wt%. The specific surface area of the rare earth oxides reaches 94.7 m2/g, and its adsorption efficiency for tetracycline hydrochloride in solution can reach 92.6% in a short time. The rare earth oxides are expected to be used as an adsorption material for wastewater treatment and other adsorption environments.

Extraction and separation of rare earth elements using LN resins in hydrochloric acid

Extraction and separation of rare earth elements using LN resins in hydrochloric acid

Computation-Aided Development of Next-Generation Extractants for Trivalent Actinide and Lanthanide Separation

Computation-Aided Development of Next-Generation Extractants for Trivalent Actinide and Lanthanide Separation

Optimization of ion-pairing HPLC method for mutual separation of rare earth elements: unveiling the “diad-effect” appraisal utilizing periodic variations in their properties

A new ion-pairing HPLC method has been developed for the analytical separation of rare earth elements (REEs), utilizing the unique “diad-effect” of the lanthanides. A chemometric approach was used to optimize the separation process, examining the impact of mobile phase pH and ion-pairing reagent concentration on resolution and elution time. A triple gradient elution program was proposed, involving changes in the pH of the mobile phase from 3.5 to 4.5, the ion-pairing reagent concentration from 25 mM to 0.05 M, and the mobile phase complexing additive (hydroxyisobutyric acid) concentration from 0.05 M to 0.5 M. With the proposed method, all REEs, including pairs that are typically difficult to separate (Pr–Nd, Eu–Gd, and Dy–Y), were effectively separated in less than eight minutes. The method validation conducted following ICH guidelines showed accurate results, with an accuracy of 99–108% across a concentration range of 50–150% of the target concentration for REEs. It also exhibited good linearity (0.9998–0.9992) across a concentration range of 5–15 µg/mL for REEs and a detection limit of 0.27–0.98 µg/mL for the various species. The proposed HPLC method proved reliable and successfully separated a commercial sample of yttrium-group oxides.

A Novel Process for the Separation of Rare Earth Elements to Recover Pure Nd(III) Solution from the NdFeB Magnets

ABSTRACT FeNdB magnets are one of the important secondary resources containing rare earth elements (REEs). The REEs present in FeNdB magnets can be separated from other metals by double salt precipitation. In order to recover pure Nd(III) solution from the double salts, separation experiments were done with the leaching solutions of the double salts containing Ce(III), Nd(III), and Pr(III). The REEs present in the double salts were completely dissolved using 0.5 M HCl solution at room temperature. First, Ce(III) was separated by oxidative precipitation of CeO2 and Ce(OH)4 by using NaClO and NaOH as an oxidizing and neutralizing agent. Complete separation of Ce(III) from the leaching solution of the double salts was possible by controlling solution pH at 5 under the following conditions: 11 for the molar ratio of NaClO/Ce(III) and 400 rpm at 40°C for 60 min. Second, all the Nd(III) and Pr(III) ions present in the filtrate were completely extracted by using saponified D2EHPA. Third, four stages of cross-current scrubbing of the loaded D2EHPA with pure Nd(III) solution removed most of the Pr(III) from the loaded D2EHPA. Finally, pure Nd(III) solution was obtained by stripping the scrubbed D2EHPA with weak HCl solution. The optimum conditions for the extraction, scrubbing, and stripping were obtained. A simple process was proposed to recover Nd(III) solution with purity higher than 99.9% from FeNdB magnets.

Selective electro-capacitive deionization of Yb(III) by nanospherical N-doped carbon supported nickel‑iron bimetallic oxide, nitride and phosphide

The separation of rare earth elements from the mining waste water is highly important but still facing challenge. In this study, three different porous composite electrode materials were well-designed by decorating the nickel‑iron bimetallic oxide, nitride or phosphide onto nitrogen-doped carbon nanosphere, respectively (termed as NiFeO@NC, NiFeN@NC and NiFeP@NC), and utilized in capacitive deionization device for electrosorption of Yb(III) from water under the low-voltage electric field. The characterization and electrochemical results indicated that the incorporation of N or P atom lead to the reduced specific surface area and the enhanced electrochemical properties (i.e., larger specific capacitance, lower charge transfer resistance). In addition, NiFeN@NC and NiFeP@NC exhibited the excellent electrosorption capacities of Yb(III) with 105.24 mg·g−1 and 90.31 mg·g−1, respectively, under conditions of a flow rate of 20 mL·min−1, a voltage of 1.2 V, and pH of 5.0, which was extremely higher than NiFeO@NC (i.e., 50.7 mg·g−1). Moreover, all these three materials also demonstrated the remarkable electrosorption selectivity of Yb(III) from the mixed solution, and the robust durability with over 90 % of initial capacities after ten consecutive electrosorption-desorption cycles. Furthermore, the XPS characterizations and electrosorption results revealed that the electrosorption mechanism mainly depended on the synergistic effects of intrinsic Faraday redox reaction, electric double layer capacitance and active binding sites. Therefore, this work provided a feasible strategy for the separation of rare earth elements from aqueous solution, and the prospective applications related to the recovery of rare earth elements from mining wastes or spent permanent magnets in future life.

X-ray Induced Cycling of Rare-Earth Elements between Bulk and Interfacial Liquid.

Reversible cycling of rare-earth elements between an aqueous electrolyte solution and its free surface is achieved by X-ray exposure. This exposure alters the competitive equilibrium between lanthanide ions bound to a chelating ligand, diethylenetriamine pentaacetic acid (DTPA), in the bulk solution and to insoluble monolayers of extractant di-hexadecyl phosphoric acid (DHDP) at its surface. Evidence for the exposure-induced temporal variations in the lanthanide surface density is provided by X-ray fluorescence near total reflection measurements. Comparison of results when X-rays are confined to the aqueous surface region to results when X-rays transmit into the bulk solution suggests the importance of aqueous radiolysis in the adsorption cycle. Amine binding sites in DTPA are identified as a likely target of radiolysis products. The molecules DTPA and DHDP are like those used in the separation of lanthanides from ores and in the reprocessing of nuclear fuel. These results suggest that an external source of X-rays can be used to drive rare-earth element separations. More generally, use of X-rays to controllably dose a liquid interface with lanthanides could trigger a range of interfacial processes, including enhanced metal ion extraction, catalysis, and materials synthesis.

Enhanced rare earth element recovery with cross-linked glutaraldehyde-lanthanide binding peptides in foam-based separations

HypothesisLanthanide Binding Tag (LBT) peptides that coordinate selectively with lanthanide ions can be used to replace the energy intensive processes used for the separation of rare earth elements (REEs). These surface-active biomolecules, once selectively complexed with the trivalent REE cations, can adsorb to air/aqueous interfaces of bubbles for foam-based REEs recovery. Glutaraldehyde, an organic compound that is a homobifunctional crosslinker for proteins and peptides, can be used to enhance the adsorption and interfacial stabilization of lanthanide-bound peptides films. ExperimentsThe stability of the interfacial cross-linked films was tested by measuring their dilational and shear surface rheological properties. Surface activity of the adsorbed species was analyzed using pendant drop tensiometry, while surface density and molecular arrangement were determined using x-ray reflectivity and x-ray fluorescence near total reflection. FindingsGlutaraldehyde cross-linked REE-peptide complexes enhance the adsorption of lanthanides to air-water interfaces, resulting in thicker interfacial structures. Subsequently, these thicker layers enhance the dilational and shear interfacial rheological properties. The interfacial film stabilization and REEs extraction promoted by the cross-linker presented in this work provides an approach to integrate glutaraldehyde as a substitute of common foam stabilizers such as polymers, surfactants, and particles to optimize the recovery of REEs when using biomolecules as extractants.

Amino Acid Decorated Phenanthroline Diimide as Sustainable Hydrophilic Am(III) Masking Agent with High Acid Resistance.

Hydrophilic actinide masking agents are believed to be efficient alternatives to circumvent the extensive hazardous organic solvents/diluents typically employed in the liquid-liquid extraction for nuclear waste management. However, the practical application of hydrophilic ligands faces significant challenges in both synthetic/purification procedures and, more importantly, the acid resistance of the ligands themselves. Herein, we have demonstrated the combination of phenanthroline diimide framework with a biomotif of histidine flanking parts could achieve efficient separation of trivalent lanthanides/actinides (also actinides/actinides) under high acidity of over 1 M HNO3. This approach leverages the soft-hard coordination properties of N, O-hybrid ligands, as well as the energetically favored imides for metal coordination and the multiple protonation of histidine. These factors collectively contribute to the synthesis of an easily accessible, highly water-soluble, superior selective, and acid-resistant Am(III) masking agent. Thus, we have shown in this paper, by proper combination of synthetic N, O-hybrid ligand with amino acid, trivalent lanthanide and actinide separation could be efficiently fulfilled in a more sustainable manner.

Highly Efficient and Precise Rare-Earth Elements Separation and Recycling Process in Molten Salt

Owing to the worldwide trend towards carbon neutrality, the number of Dy-containing heat-resistant Nd magnets used for wind power generation and electric vehicles is expected to increase exponentially. However, rare earth (RE) elements (especially Dy) are unevenly distributed globally. Therefore, an environmental-friendly recycling method for RE elements with a highly precise separation of Dy and Nd from end-of-life magnets is required to realize a carbon-neutral society. As an alternative to traditional hydrometallurgical RE separation techniques with a high environmental load, we designed a novel, highly efficient, and precise process for the separation and recycling of RE elements from magnet scrap. As a result, over 90% of the RE elements were efficiently extracted from the magnets using MgCl2 and evaporation loss was selectively suppressed by adding CaF2. The extracted RE elements were electrolytically separated based on the formation potential differences of the RE alloys. Nd and Dy metals with purities greater than 90% were estimated to be recovered at rates of 96% and 91%, respectively. Almost all the RE in the scraps could be separated and recycled as RE metals, and the byproducts were easily removed. Thus, this process is expected to be used on an industrial scale to realize a carbon-neutral society.