Separation Of Lanthanides Research Articles

A task-specific ionic liquid based on hydroxypyridinone for lanthanide separation

A 1,2-hydroxypyridinone (HOPO) grafted ionic liquid (HOPO-IL) was synthesized for the first time and characterized by NMR spectroscopy and mass spectrometry. The solvent extraction of this HOPO-IL used as an extractant for lanthanide separation in various ionic liquids (ILs) and organic solvent was investigated, revealing enhanced extraction performance in the IL solvents. The extraction performance increased by ∼2 folds in ILs than in organic solvent. The extraction behavior of this HOPO-IL extractant was also compared in aqueous solutions under different acidities. The effects of aqueous phase acidity and the additions of an IL’s cation or anion to the aqueous phase on separation properties of lanthanides are studied, indicating a strong pH-dependence and a dominant cation-exchange mechanism of lanthanide extraction.Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (https://energy.gov/downloads/doe-public-access-plan).

Rational Technology for Separation of Rare-Earth Elements of the Yttrium Group

Rational Technology for Separation of Rare-Earth Elements of the Yttrium Group

Separation of rare earth elements from a South American ionic clay lixivium by sequential precipitation

Ionic clays, formed by natural weathering of rare earth element (REE)-containing minerals and surface adsorption of liberated ions, are a critical REE resource. Here, the sequential precipitation of impurities and REEs from the desorption of a South American ionic clay is investigated. Selective sequential precipitation profiles are constructed by stepwise addition of 1.3 M ammonium bicarbonate to the lixivium. During sequential precipitation, ammonium bicarbonate first behaves as a pH adjustor to remove co-extracted impurities as hydroxides, and then behaves as both a carbonate ion source and a pH adjustor to precipitate the REEs as carbonates. Impurity precipitation is completed at pH 6.0 and REE precipitation is completed at pH 6–7.5; however, total carbonate concentration during the impurity precipitation step must be kept low to prevent REE loss. To gain a better understanding of the REE precipitation step, thermodynamic calculations using the Davis model are performed. Dysprosium is studied as a model REE and its speciation diagram as a function of pH and total carbonate and sulfate ion concentrations is constructed. It is found that the primary factors controlling REE precipitation are pH, carbonate, and sulfate concentrations. The knowledge gained in this work provides a deeper understanding of the sequential impurity and REE precipitation processes from the desorption lixivium of a unique ionic clay from South America. The results would help guide future work on REE separation from this distinct ionic clay.

Efficient sorption and group separation of rare earth elements using modified CuO nanocomposite

Radioactive waste from aquatic nuclear power plants includes long-lived radiotoxic trivalent lanthanides. Because of the growing demand for rare-earth elements (REEs) in high-tech applications, new sustainable approaches to REE recycling and separation have been developed. Separation of rare earth elements (REEs) is extremely difficult due to their similarity in properties. Also, Fe2O3 is the major contaminant of REE recovery. As a result, the purpose of this work is to create a novel nano composite, sodium alginate grafted polyacrylic acid/CuO, SA-g-(PAA/CuO). Modified nano CuO is prepared using sol-gel technique and calcinied at 600 °C/2h. The SA-g-(PAA/CuO) nanocomposite was created using free radical polymerization with 60 Co gamma irradiation at a dose of 25 KGy. The prepared composite was characterised by FT-IR, XRD, TG-DTA, SEM, particle size analysis, TEM, and pore size distribution. SA-g-(PAA) with 10% nano CuO, SA-g-(PAA/CuO)-II, is investigated for the sorption of light rare earth elements (La3+, Ce3+) and intermediate rare earth elements (Eu3+) at 25 °C and heavy rare earth elements (Y3+) at pH 4.5. Sorption of contaminants (Fe3+) is studied at pH 2.5. The equilibrium of sorption reaction is attained at 5 h. The obtained results showed that the monolayer capacities for La3+, Ce3+, Eu3+, Fe3+, and Y3+ are 83.68, 90.83, 94.69, 24.66, and 7.52 mgg-1, respectively. SA-g-(PAA/CuO)-II nanocomposite efficiently separates La3+, Ce3+, and Eu3+ from Fe3+ and Y3+.

Prompt digestion and HPIC separation of rare earth elements in surrogate post-detonation debris material with detection by ICP-MS and gamma spectroscopy

Prompt analysis of fission products and rare earth elements (REE)s in post-detonation nuclear debris is critical for nuclear forensic analysis. In this work the compatibility of ammonium biflouoride fusion and microwave digestion in combination with high pressure ion chromatography (HPIC) separation was examined for the analysis of REEs. The refractory geological materials USGS G-2, QLO-1a, AGV-2 and BHVO-2 were used as surrogate post-detonation debris. The HPIC separation used a mixed bed ion exchange column with a gradient elution consisting of oxalic acid and diglycolic acid mobile phases. Quantitative recovery for seven REEs was achieved using the in-line HPIC-ICP-MS. An off-line HPIC method was also developed to separate U, Pu, and REE fission products. Collected fractions were analyzed by ICP-MS or gamma ray spectroscopy. The offline HPIC separation with detection of short-lived fission products with gamma ray spectroscopy had detection limits 5–20,000 times lower than quadrupole ICP-MS for stable REEs.

Efficient Recovery of Rare Earth Elements and Zinc from Spent Ni-Metal Hydride Batteries: Statistical Studies.

Considering how important rare earth elements (REEs) are for many different industries, it is important to separate them from other elements. An extractant that binds to REEs inexpensively and selectively even in the presence of interfering ions can be used to develop a useful separation method. This work was designed to recover REEs from spent nickel–metal hydride batteries using ammonium sulfate. The chemical composition of the Ni–MH batteries was examined. The operating leaching conditions of REE extraction from black powder were experimentally optimized. The optimal conditions for the dissolution of approximately 99.98% of REEs and almost all zinc were attained through use of a 300 g/L (NH4)2SO4 concentration after 180 min of leaching time and a 1:3 solid/liquid phase ratio at 120 °C. The kinetic data fit the chemical control model. The separation of total REEs and zinc was conducted under traditional conditions to produce both metal values in marketable forms. The work then shifted to separate cerium as an individual REE through acid baking with HCl, thus leaving pure cerium behind.

The selective adsorption of rare earth elements by modified coal fly ash based SBA-15

The modification of fly ash based SBA-15 enables the selective adsorption of REE(III) with a high capacity. • The species distribution of rare earth elements ions was simulated. • DTPADA-SBA-15 owned high adsorption efficiency and selectivity for REE (III). • DTPADA-SBA-15 owned preferable reusability in acidic solution. Rare earth elements (REE) are strategic resources and the recycling of REE in alternative resources is urgent and gets increasingly attention. However, the separation of REE in these alternative resources is still a challenge due to the low concentration of REE and multi coexisted ions in acidic system. In this study, the species distribution of REE within the pH 0–8.0 was calculated. The SBA-15 originated from coal fly ash was modified by two steps with (3-aminopropyl) triethoxysilane (APTES) and diethylenetriaminepentaacetic dianhydride (DTPADA) to obtain DTPADA-SBA-15 adsorbent, which was applied to the selective adsorption of REE. The results showed that DTPADA-SBA-15 possessed excellent adsorption performance on the selective adsorption of REE, including Eu, Gd, Tb, Nd and Sm, in acidic solution (pH 2) with multi competing ions. The FT-IR and Zeta potential characterization verified that the chemical adsorption through the coordination of O in DTPADA-SBA-15 with REE was dominant at lower pH value. The study of adsorption kinetics indicated that the adsorption of rare earth metal ions followed pseudo-second-order kinetic, of which the adsorption process followed the Langmuir isotherm model.

Application of silica-based sorbents to extraction of rare earth elements from loparite processing products

Apatite and loparite are the main sources of rare earth elements (REE) in Russia. Loparite is a complex titanate and niobate containing up to 30% wt. of REE oxides predominantly of the cerium group. Extraction processing methods are used at the stages of group separation and separation of REE concentrates. Tributyl phosphate (TBP) is a widely used extracting agent for these purposes. Extraction technologies have a number of disadvantages, in particular, a large number of separation stages because of low separation coefficients of individual REE combined with difficulties in separating liquid phases. The use of TBP-containing sorbents allows to eliminate the latter disadvantage. Both organic polymers and inorganic compounds may be used as sorbent carriers; among inorganic ones, silica is widely used, and it was selected for this study. The purpose of this work was to study the effect of variations of the proposed methods for synthesis of silica and modified TBP based sorbents on their ability to extract REE from the solutions of loparite concentrate processing. The article briefly describes a procedure for sorbent samples synthesis. Tetraethoxysilane, tributyl phosphate, stannic chloride and nanotubes have been used as starting reagents for the synthesis. A number of physicochemical properties have been determined for the synthesized samples (pore volume and their average diameter, surface area and morphology, acid-base properties of the surface), and thermogravimetric analysis has been performed. The sorption properties of the samples have been tested by the example of REE extraction from process solutions of loparite working up. The separation coefficients of Sm/La pairs up to 3.7, Pr/Nd up to 1.8 were obtained; therefore, the studied samples may be potentially used for samarium isolation from the REE combination, as well as for Pr – Nd pair separation. This study was supported by the Tomsk State University Development Programme (Priority-2030).The SEM researches and results of measuring the specific surface area (SBET) and porous structure were carried out with the equipment of Tomsk Regional Core Shared Research Facilities Center of National Research Tomsk State University. Center was supported by the Ministry of Science and Higher Education of the Russian Federation Grant no. 075-15-2021-693 (no. 13.RFC.21.0012)).

Selective separation of low concentration rare earths via coordination-induced ion imprinted electrospun membranes

How to efficiently utilize the low-concentration rare earth wastewater has become an urgent demand for the sustainable mining and resource utilization of ion-type rare earth minerals in China. Herein, we developed Y ion-imprinted electrospun membranes (Y-IIEMs) for the selectively separation of neighboring heavy rare earth ion Y(III) from Ho(III) and Er(III) by applying high efficient ligand-inducing and aqueous phase ion-imprinting. Cyanex272 was applied as carrier in membrane matrix and also as high-efficient ionic ligand in imprinted layer. Thermal stability of Cyanex272 was greatly improved after pDA bionic adhesion and sol-gel aqueous phase imprinting. Water contact angle of Y-IIEMs was only 23.2° which was probably a combination result from all the polar groups PO and P–OH from Cyanex 272 ligand, the imino groups from pDA layer and the silicon hydroxyls from sol-gel imprinting. And the calculated static adsorption imprinting factor of Y(III) was more than 7 indicating that valid recognition sites were successfully formed. The separation factors β(Y/Ho) and β(Y/Er) in dynamic permeation process increased significantly from 1.24 and 0.85 for non-imprinting to 2.01 and 1.77 for imprinting membranes. After 8 cycles of dynamic permeation, Y-IIEMs’ flux decreased only 13.8%, which implied good stability and reuse performance.

Advancing Rare-Earth Separation by Machine Learning.

Constituting the bulk of rare-earth elements, lanthanides need to be separated to fully realize their potential as critical materials in many important technologies. The discovery of new ligands for improving rare-earth separations by solvent extraction, the most practical rare-earth separation process, is still largely based on trial and error, a low-throughput and inefficient approach. A predictive model that allows high-throughput screening of ligands is needed to identify suitable ligands to achieve enhanced separation performance. Here, we show that deep neural networks, trained on the available experimental data, can be used to predict accurate distribution coefficients for solvent extraction of lanthanide ions, thereby opening the door to high-throughput screening of ligands for rare-earth separations. One innovative approach that we employed is a combined representation of ligands with both molecular physicochemical descriptors and atomic extended-connectivity fingerprints, which greatly boosts the accuracy of the trained model. More importantly, we synthesized four new ligands and found that the predicted distribution coefficients from our trained machine-learning model match well with the measured values. Therefore, our machine-learning approach paves the way for accelerating the discovery of new ligands for rare-earth separations.

Separation of rare earths in chloride media by synergistic solvent extraction with mixture of HEHAMP and CA12 and stripping with HCl

The synergistic extraction of rare earths (REs) from chloride media by a mixture of two extractants 2-ethylhexylaminomethyl phosphonic acid mono-2-ethylhexyl ester (HEHAMP, HA) and sec-octylphenoxy acetic acid (CA12, HB) was investigated. A remarkable positive synergistic effect was observed at the molar ratio of HEHAMP to CA12 being of 2:3. The extraction of REs was found to be a cation exchange process and the extracted species of Yb3+ was determined as YbCl2HAB. The separation factors (SF) of adjacent heavy REs, i.e. SFYb/Tm and SFLu/Yb, for the mixtures were 2.50 and 1.63, which were much higher than those of the sole HEHAMP and the sole CA12 system. In additional, the values of SFYb/Y and SFLu/Y were 7.17 and 11.14, respectively, which were higher than those of other reported synergistic systems and those of the sole HEHAEP or CA12 system, suggesting that the mixture of HEHAMP and CA12 is a potential synergistic extraction system for the separation of heavy REs and/or Y(III) from other heavy REs. A cascade extraction process for the separation of Y(III) from yttrium-enriched REs feed using the synergistic extraction system was developed, which are superior to sole CA12 system. The Y2O3 product with a purity of 99.4% was obtained by 8 extraction stages and 5 scrubbing stages.

Comparative DFT study of americium and europium complexation with 2,9-bis(1,2-diazin-3-yl)-1,10-phenanthroline ligand in gas phase

2,9-bis(1,2,4-triazin-3-yl)-1,10-phenantroline (BTPhen) based ligands have shown great promise in separation of trivalent lanthanides and actinides. Although many experimental studies have shown that americium is forming stronger complexes with the BTPhen ligands than europium, most theoretical studies have thus far failed to reproduce these results. In the current study, two different metal forms (the naked cation and its tetraaquatrinitrato complex) were used to study five different complexation reactions. It was shown that in case of naked cations europium forms the most stable complex with the 2,9-bis(1,2-diazin-3-yl)-1,10-phenanthroline (BTPhen-CH) ligand in all of the compared reactions. In case of tetraaquatrinitrato complex it was shown that europium gets a higher stabilizing effect and thus americium complexes with BTPhen-CH become the more stable form, as can be seen in the experimental studies.

Separation of Rare Earth and Aluminum by Selective Complexation

The presence of aluminum in the weathering crust leaching rare earth ore harms the subsequent extraction and separation of rare earths. High-quality rare earth production processes must reduce the aluminum content in their feed liquid. Groups containing lone pairs of electrons can form stable insoluble complexes with metal ions under certain conditions. In this paper, 3-hydroxyphenylphosphoryl propionic acid is used to selectively separate rare earths by complexation in feed liquid. The results show that: using 3-hydroxyphenylphosphoryl propionic acid as the complexing agent, and when the amount of 3-hydroxyphenyl phosphoryl propionic acid is six times the theoretical complete reaction amount, the reaction time is 10 min, the reaction temperature is 50 °C, and the solution is adjusted to pH 1, the extraction rate of RE3+ is 90.48%, and the extraction rate of Al3+ is nearly 9.52%. The separation of rare earth and aluminum is well realized. 3-hydroxyphenyl phosphoryl propionic acid has good water solubility and low cost, and the product after complexation reaction with metal ions is solid and easy to separate. It has potential as an alternative complexing agent in the industry.

Atomistic Insights into Structure and Dynamics of Neodymium(III) Complexation with a Bis-lactam Phenanthroline Ligand in the Organic Phase.

Rare-earth elements (REEs) such as neodymium are critical materials needed in many important technologies, and rigid neutral bis-lactam-1,10-phenanthroline (BLPhen) ligands show one of the highest extraction performance for complexing Nd(III) in REE uptake and separation processes. However, the local structure of the complexes formed between BLPhen and Nd(III) in a typical organic solvent such as dichloroethane (DCE) is unclear. Here, we perform first-principles molecular dynamics (FPMD) simulations to unveil the structure of complexes formed by BLPhen with Nd(NO3)3 in the DCE solvent. BLPhen can bind to Nd(III) in either 1:1 or 2:1 fashion. In the 1:1 complex, three nitrates bind to Nd(III) via the bidentate mode in the first solvation shell, leading to the formation of a neutral complex, [Nd(BLPhen)(NO3)3]0, in the organic phase. In contrast, there are two nitrates in the first solvation shell in the 2:1 complex, creating a charged complex, [Nd(BLPhen)2(NO3)2]+. The third nitrate was found to be far away from the metal center, migrating to the outer solvation shell. Our simulations show that the binding pocket formed by the two rigid BLPhen ligands allows ample space for two nitrates to bind to the Nd(III) center from opposite sides. Our findings of two nitrates in the first solvation shell of the 2:1 complex and the corresponding bond distances agree well with the available crystal structure. This study represents the first accurate FPMD modeling of the BLPhen–Nd(III) complexes in an explicit organic solvent and opens the door to more atomistic understanding of REE separations from first principles.

Thiocyanate Ions Form Antiparallel Populations at the Concentrated Electrolyte/Charged Surfactant Interface.

Anions play significant roles in the separation of lanthanides and actinides. The molecular-scale details of how these anions behave at aqueous interfaces are not well understood, especially at high ionic strengths. Here, we describe the interfacial structure of thiocyanate anions at a soft charged interface up to 5 M bulk concentration with combined classical and phase-sensitive vibrational sum frequency generation (PS-VSFG) spectroscopy and molecular dynamics (MD) simulations. At low concentrations thiocyanate ions are mostly oriented with their sulfur end pointing toward the charged surfactants. The VSFG signal reaches a plateau at around 100 mM bulk concentration, followed by significant changes above 1 M. At high concentrations a new thiocyanate population emerges with their sulfur end pointing toward the bulk liquid. The -CN stretch frequency is different for up and down oriented SCN- ions, indicating different coordination environments. These results provide key molecular-level insights for the interfacial behavior of complex anions in highly concentrated solutions.

A novel functionalized ionic liquid [DOC4mim][DEHG] for impurity removal of aluminum in rare earth leaching solution

The separation of rare earth (RE) and aluminum (Al) has always been a practical challenge. In this article, a novel functionalized ionic liquid 1-butyl-3-(3,3-dimethyl-2-oxobutyl)-imidazol-3-ium bis(2-ethylhexyl)glycinate ([DOC4mim][DEHG]) with high selectivity was developed for the impurity removal of Al from ion-adsorbed type RE ores leaching solution. In the sulfuric acid system, the ionic liquid extracted Al through an ion association mechanism. Salting out agent of Na2SO4 could change the stoichiometric number of extraction equilibrium. For the actual RE leaching solution, the inhibitory effect exhibited by Na2SO4 prevented more RE elements from being removed together with Al. Under the optimized extraction conditions, the removal rate of Al was more than 95%, also the recovery rate of RE was more than 96%. Compared with saponified industrial extractant naphthenic acid, it revealed better interface phenomenon and higher RE recovery performance. NaOH solution with low concentration could be used to strip and regenerate RE-loaded [DOC4mim][DEHG] at the same time. In five cycles, the extraction system maintained good reproducibility. There was no acid consumption in the separation process. This work provides a new insight into the efficient and sustainable removal of Al impurity from actual RE leaching solution.

Effect of polar molecular organic solvents on non-aqueous solvent extraction of rare-earth elements

The extraction and separation of five different rare-earth elements, La, Nd, Eu, Dy and Yb, from an aqueous chloride solution and from different chloride non-aqueous solutions using the solvating extractant Cyanex 923 was investigated. As previous studies had demonstrated the potential of non-aqueous solvent extraction (NASX) to refine rare earths from ethylene glycol, structural analogues of ethylene glycol (1,2-propanediol and 1,3-propanediol) and to other polar organic solvents (triethylene glycol, dimethylsulfoxide, methanol, N,N-dimethylformamide and N,N-dimethylacetamide) were studied. The extraction data were interpreted in terms of different solvent properties: dielectric constant, Gutmann donor number, molecular structure and hydrogen-bonding capabilities. Remarkable differences were observed between the extraction behaviour from ethylene glycol, 1,2-propanediol and 1,3-propanediol. Therefore, these solvent systems were further studied to elucidate the speciation of the rare-earth elements by optical absorption and luminescence spectroscopy. Based on these studies, both contact-ion-pair formation and solvation strength are assumed to play an important role in the extraction of rare earths by Cyanex 923 from different polar organic solvents. The differences in extraction behaviour can be exploited to fine-tune the separation of rare earths.

Investigating Landmodulin's EF Hands in Relation to Lanthanide Recycling Methods

Rare earth elements (REEs) have distinct and varied electronic properties that have been applied for military and civilian use in electronics, such as cell phones and computer chip technologies. The recycling methods for REEs are complex and require a multitude of resources that prompt new studies to improve REEs separations. Lanmodulin (LanM), a protein that naturally bind to lanthanides, may provide a biological route for REE separation. Understanding the structure of LanM’s EF‐hands will explain how the lanthanides bond to them and lead to a greater understanding of how LanM can be used to recycle REEs to benefit our environment. The Summit Country Day School MSOE Center for BioMolecular Modeling MAPS Team used 3D modeling and printing technology to examine structure‐function relationships of EF1‐3 hands on lanmodulin. LanM has three tight binding EF‐hands, EF1 (D35‐E46), EF2 (D59‐E70), and EF3 (D84‐ E95), which are abundant in carboxylate side chains that bind the lanthanides. Lanthanide binding promotes a large conformational shift of the protein from a disorganized state to an organized state. The interior of the protein is a condensed helical bundle, and the majority of the exterior is composed of the EF hands, making bonding with lanthanides easier due to the EF hands being solely on the exterior. These three hands contain a higher number of coordination numbers (8‐9) compared to only 7 in Calmodulin (CaM), resulting in more specialized bonding properties. LanM also has a conserved proline between the first and second putative metal‐coordinating residues in each of the four EF hands, which is unique to this protein and may play a role in reducing affinity for calcium ions. In conclusion, analyzing the properties of the binding sites of EF1‐3 in LanM through 3D modeling can reveal insights on utilizing proteins as a method to extract and recycle REE in order to be environmentally cognizant.

A new finding and technology for selective separation of different REEs from CaO-SiO2-CaF2-P2O5-Fe3O4-RE2O3 system

The significant increase in global consumption of rare earth elements (REEs) has attracted more attention to the separation of REEs from complex rare-earth systems. Bayan Obo ore is the world’s largest rare-earth deposit, where REEs are mainly transfered to RE-concentrate which contains various species of REEs (mainly includes lanthanide: Ce, La, Pr, and Nd). This study reported a new finding and technology for selective separation of different REEs from Bayan Obo RE-concentrate system. The basic data on phase transformation of different REEs in CaO-SiO2-CaF2-P2O5-Fe3O4-RE2O3 systems were reported, and firstly found that different REEs of Ce, La, Pr and Nd could be selectively enriched into cerium oxide, lanthanum ferrate, praseodymium apatite and neodymium apatite, respectively. A novel technology of separating RE-phases via super gravity was proposed, various high-purity RE-phases containing different REEs were separated and characterized, and the crystal information missing in the current database were supplemented.

Improving Rare-Earth Mineral Separation with Insights from Molecular Recognition: Functionalized Hydroxamic Acid Adsorption onto Bastnäsite and Calcite.

Enhancing the separation of rare-earth elements (REEs) from gangue materials in mined ores requires an understanding of the fundamental interactions driving the adsorption of collector ligands onto mineral interfaces. In this work, we examine five functionalized hydroxamic acid ligands as potential collectors for the REE-containing bastnäsite mineral in froth flotation using density functional theory calculations and a suite of surface-sensitive analytical spectroscopies. These include vibrational sum frequency generation, attenuated total reflectance Fourier transform infrared, Raman, and X-ray photoelectron spectroscopies. Differences in the chemical makeup of these ligands on well-defined bastnäsite and calcite surfaces allow for a systematic relationship connecting the structure to adsorption activity to be framed in the context of interfacial molecular recognition. We show how the intramolecular hydrogen bonding of adsorbed ligands requires the inclusion of explicit water solvent molecules to correctly map energetic and structural trends measured by experiments. We anticipate that the results and insights from this work will motivate and inform the design of improved flotation collectors for REE ores.