Extraction Of Lanthanides Research Articles

Preparation of magnetic oil-based gel microspheres containing di(2-ethylhexyl)phosphoric acid for extraction of scandium ions at low concentrations in aqueous solutions

Extraction of low-concentration rare earths is one of the important paths for the sustainability of the rare earth industry. The research and development of materials suitable for the extraction of rare earth ions at low concentrations is of great significance. Currently, the application of solvent extraction in the rare earth production industry is highly mature. However, it is not economical to use it for the extraction of low concentration rare earths with problems of phase separation and organic phase loss. This work innovatively proposes to encapsulate the extractant and diluent in magnetic oleogel microspheres, which are obtained by solubilizing magnetic poly (phenyl divinylbenzene)(PS-DVB) microspheres with the extractant and diluent.. The magnetic PS-DVB microspheres of 3 ∼ 16 μm were prepared by suspension polymerisation, followed by encapsulation of di(2-ethylhexyl)phosphoric acid (D2EHPA) and dichloroethane in magnetic PS-DVB microspheres using emulsion swelling, and then magnetic oil-based gel microspheres containing D2EHPA with a particle size of 10 ∼ 32 μm were obtained. The magnetic oil-based gel microspheres containing D2EHPA consist of about 96 wt% liquid phase and about 4 wt% solid phase, with D2EHPA accounting for more than 4.19 wt%. The magnetic oil-based gel microspheres are very close to small oil droplets and are superparamagnetic. The magnetic oil-based gel microspheres containing D2EHPA could completely extract 60 ppm of scandium ions(Sc3+) under the conditions of O:A = 1:50,1:60,1:70, and the extraction equilibrium times were 6, 9 and 12 min, respectively. This extractant encapsulation scheme inherits the selectivity of traditional extractants while simultaneously preserving the advantages of rapid extraction by solvent extraction.

Rare earth element extraction from geothermal brine using hybrid capacitive-deionisation process

Rare Earth Elements (REE) in geothermal brine include pollutants such as dissolved Lanthanum, Cerium, Praseodymium, Neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, lithium, and other ions. These REEs in geothermal brine, also popularly known as “Vitamins of the modern industry”, are vital for industries such as new energy vehicles, wind turbines, radar systems, laser crystals, etc., and harmful for agriculture and drinking purposes. Hence, identifying, quantifying, and extracting these REEs are essential and economical for a geothermal plant. The present study systematically investigates identifying and quantifying the REE and other essential ions in geothermal brine sources from Gujarat regions. For the extraction of REE from geothermal brine, geothermal brine treatment systems and their integration with automation control are designed in the present work. The proposed system filters geothermal brine and extracts REE through a hybrid filtration setup using capacitive deionization. Solar photovoltaic Water Filtration uses a hybrid Capacitive De-Ionization (CDI) treatment-based prototype to purify water and extract REE. The CDI method is an emerging technology in the desalination systems. It has far greater leverage over other desalination methods such as electrodialysis. The proposed design allows the simultaneous removal of various dissolved organic and inorganic contaminants in geothermal brine.

Bioleaching of rare earth elements (REEs) from Indonesian red mud by the bacterium Bacillus nitratireducens strain SKC/L-2

Red mud, a residue of the bauxite industry, represents a secondary source of rare earth elements (REEs) with substantial commercial value and untapped potential. Bioleaching, an innovative, cost-effective, and environmentally friendly method, offers a means of extracting valuable metals from mining wastes. This study explored the bioleaching of Indonesian red mud using Bacillus nitratireducens strain SKC/L-2 to recover REEs. The experiments were carried out over three days at 25 °C with different concentrations of red mud (1.5, 3, and 6 g/L) and a 10% v/v bacterial inoculum in a specific bioleaching medium. The findings indicated a slight reduction in REEs extraction by the bacterium as the red mud concentration increased from 1.5 to 6 g/L in the direct bioleaching process. In the experiment using 1.5 g/L red mud, 16 REEs were successfully extracted, with high extraction levels for specific elements such as Lu (92.0%), Tb (80.61%), and Gd (67.42%). However, when the red mud concentration was increased to 6 g/L, the survival potential of Bacillus nitratireducens strain SKC/L-2 decreased, leading to reduced recovery of elements such as Lu (76.80%), Tb (70.30%), and Gd (55.83%). The study reveals the behaviour of Bacillus nitratireducens in interacting with red mud and enduring high alkalinity, resulting in REEs extraction. These findings enhance the understanding of microbial interactions with red mud and provide insights into potential resource recovery applications.

Preparation of phosphorylated conjugated microporous organic polymers and extraction of low-concentration rare earth elements

Aiming at the extraction and recovery of rare earth elements (REEs) in low-concentration rare earth leaching tailings, a kind of phosphorylated conjugated microporous organic polymer (P-CMP) was prepared and applied to adsorb rare earth ions (Nd3+, Dy3+, Y3+). The structure of P-CMP was characterized by FT-IR. SEM and EDS were utilized to illustrate the surface morphology and element distribution of P-CMP, respectively.The adsorption mechanism of P-CMP was determined by XPS. The effects of pH, ion concentration and adsorption time on adsorption capacity were investigated. The isotherm of the rare earth adsorption process was fitted by Langmuir and Freundlich models, and the kinetics was fitted by Pseudo-firstorder and Pseudo-second-order. The results show that P-CMP is an amorphous microporous material, which has strong interaction with Nd3+ (30.18 mg/g), Dy3+ (37.84 mg/g) and Y3+ (22.01 mg/g), and the synergistic effect of amino and phosphate groups provides good selectivity (S.F.(Nd3+/Men+) = 5*103~5*104). The PCMP selectively adsorbs rare earth ions in the actual system and cycles 8 times.

Effect of ion to ligand ratio on the aqueous to organic relative solubility of a lanthanide-ligand complex.

In the solvent extraction of rare earth elements, mechanistic aspects remain unclear regarding where and how extractant molecules coordinate metal ions and transport them from the aqueous phase into the organic phase. Molecular dynamics simulations were used to examine how unprotonated di(2-ethylhexyl)phosphoric acid (DEHP-) ligands that coordinate the Gd3+ ion can transfer the ion across the water-organic interface. Using the umbrella sampling technique, potential of mean force profiles were constructed to quantify the relative solubility of the Gd3+ ion coordinated to 0-3 DEHP- ligands in either water, 1-octanol, or hexane solvents and at the water-organic interfaces. The simulations show the Gd-DEHP- complexes, at varying Ln-ligand ratios, preferentially solvate on water-organic interfaces. While the Gd(DEHP-)3 complex will diffuse past the aqueous-organic interface into the octanol solvent, it is thermodynamically preferred for the Gd(DEHP-)3 complex to remain in the water-hexane interface when there is no amphiphilic layer of excess ligand.

Flow-driven enhancement of neodymium and dysprosium separation from aqueous solutions

Flow-induced non-equilibrium conditions yielded high-purity Dy precipitate from aqueous mixtures of NdCl3 and DyCl3 more quickly compared to conventional equilibrium stirred mixing.

Research of Bayan Obo tailings characteristics and recovery methods

This paper presents a new method for the recovery of iron and rare earth elements (REEs) from Bayan Obo tailings, which are the waste materials from the extraction of iron and REEs from the Bayan Obo ore deposit in Inner Mongolia, China. The method is based on the combination of microwave-assisted carbothermal reduction and acid leaching. The microwave-assisted carbothermal reduction can effectively reduce the iron oxides and REE oxides in the tailings to metallic iron and REE metals, respectively, and separate them from the gangue minerals. The acid leaching can then dissolve the REE metals from the reduced product and obtain a high-purity REE solution. The effects of various parameters on the performance of the method were investigated and optimized, and the mechanisms and kinetics of the reactions were analyzed and modeled. The results showed that the method can achieve a high recovery rate of iron and REEs, a high selectivity of REEs, a low energy consumption, and a simple process. The economic and environmental benefits of the method are also significant, as it can utilize the Bayan Obo tailings and recover the valuable elements from them, and reduce the waste generation and greenhouse gas emission. The method provides a new and efficient technology for the utilization of Bayan Obo tailings and the recovery of iron and REEs, and contributes to the fundamental understanding of the microwave-assisted carbothermal reduction and acid leaching processes.

IMPACTS OF AMMONIUM SULFATE LEACHING ON ION ADSORPTION RARE EARTHS AND SOIL MECHANICAL PROPERTIES

In-situ leaching (ISL) has gained prominence as a non-destructive method for rare earth element (REE) extraction, particularly in regions like China. However, concerns over the environmental impact and soil stability due to ISL activities have surfaced following a landslide incident. This article distills the essence of a comprehensive research endeavor that delves into the effects of ammonium sulfate ISL leaching, employing concentrations of 0.05M, 0.1M, and 0.5M, on soil mechanical properties. The study encompasses physicochemical, physical, and mechanical tests, unveiling substantial alterations in shear strength, cohesion, angle of internal friction, zeta potential, liquid limit, plastic limit, and plasticity index following leaching. XRF and XRD analyses reveal the presence of REEs and distinctive mineral phases in the soil samples. Overall, ISL induces a weakening of the soil, raising concerns about potential slope failures and emphasizing the need for a deeper understanding of ISL’s impact on soil properties in the context of REE mining.

Theoretical investigation on the ligands constructed from phenanthroline and five-membered N-heterocyclic rings for bonding and separation properties of Am(III) and Eu(III).

The ligands, derived from the combination of phenanthroline and various five-membered N-heterocyclic rings, were subject to a comprehensive investigation for their potential in the extraction and separation of actinides and lanthanides. This study employed DFT methods to thoroughly explore the properties of both phenanthroline (Ph) and the diverse five-membered N-heterocyclic rings (R1-R8). Additionally, tridentate ligands RlPh (l = 1-8) and tetradentate ligands RlPhRr (l, r = 1-8) were analyzed in detail, encompassing their electrostatic potential (ESP), protonation energy, coordination bonding with the metals Am(III) and Eu(III), and the thermodynamics of extraction separation for Am(III) and Eu(III). The findings highlight that the electrostatic potential (ESP) and binding capabilities of the five-membered N-heterocyclic ring units serve as effective predictors for the properties of intricate tridentate and tetradentate ligands, as well as their coordination bonding affinity with metals. The ligands' binding energy is closely associated with their ESP, and notably, the binding energy of tridentate and tetradentate ligands correlates well with the binding energies of their constituent structural units. The computational results reveal that the R2 unit, along with its corresponding tridentate ligand R2Ph and tetradentate ligands R2PhRr, exhibits the highest ESP, superior binding energies, and the strongest coordination bonding affinity with the metals. The theoretical calculations further identify several promising extractants for the effective separation of Am(III) and Eu(III). The tridentate ligands R1Ph, R7Ph, and R4Ph, and the tetradentate ligands R4PhR4, R6PhR6, R2PhR2, R1PhR5 and R3PhR6 were identified as having excellent separation performance for Am(III) and Eu(III). This study would provide insights for the design of extractants for the separation of Am(III) and Eu(III) by use of five-membered N-heterocyclic rings as structural units.

The role of fluocerite in the genesis of bastnäsite: mechanistic insights and transformation pathways.

Fluocerite is a rare earth element (REE) fluoride found as an accessory mineral in magmatic-hydrothermal REE ore deposits, including alkaline complexes and carbonatites, where it is often associated with REE-fluorocarbonates. This study investigates the crystallisation kinetics, mechanisms and energetics of fluocerite (REEF3) and its role as a precursor phase of bastnäsite, one of the key minerals used for the extraction of REE. Fluocerite was synthesized by reacting pure fluorite (CaF2) with La-, Ce- and Nd-bearing solutions at temperatures ranging from ambient to low hydrothermal (30-90 °C). The synthetic fluocerites were then placed in contact with Na2CO3 solutions at temperatures up to 200 °C. A combined approach using powder X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy was used to determine the nature and quantify the crystallising solids. Our findings reveal a temperature-dependent fluorite-fluocerite transformation, with completion observed within 1 hour at 90 °C and extending to around 30 days at 30 °C. The rate of crystallisation decreases proportionally with the atomic number of the rare earth elements. On the other hand, the carbonation reaction of fluocerite exhibits a significantly slower rate, by ∼3 orders of magnitude, in comparison to the fluorite-fluocerite transformation, regardless of temperature conditions. The synthetic La, Ce and Nd fluocerites transformed into bastnäsite at all temperatures, also forming cerianite (CeO2) in the Ce-bearing experiments and metastable kozoite, NdCO3OH(orth), in the Nd-bearing experiments. Activation energies of fluocerite nucleation increase proportionally with the ionic radii of the REE (81 ± 6 (La); 84 ± 5 (Ce), 96 ± 10 (Nd) kJ mol-1), while the activation energies associated with fluocerite crystallisation are slightly higher for La (90 ± 12 kJ mol-1) and similar for Ce and Nd (76 ± 12 and 72 ± 8 kJ mol-1, respectively).

Agile synthesis and automated, high-throughput evaluation of diglycolamides for liquid–liquid extraction of rare-earth elements

The study presents a scalable and sustainable extraction method for rare earth, featuring a green, scalable synthesis of diglycolamides that reduces greenhouse gas emissions by 67% and a liquid-liquid extraction workflow.

Metadynamics investigation of lanthanide solvation free energy landscapes and insights into separations energetics.

Lanthanide ion solvation chemistry in nonaqueous phases is key to understanding and developing effective separation processes for these critical materials. Due to the complexity and inherent disorder of the solution phase, a comprehensive picture of the solvated metal ion is often difficult to generate solely from conventional spectroscopic approaches and electronic structure calculations, particularly in the extractant phase. In this work, we use classical molecular dynamics (MD) simulation with an advanced sampling technique, metadynamics, supplemented by experimental spectroscopy and speciation analysis, to measure lanthanide solvation free energy landscapes. We define coordination-based collective variables to probe the entire range of solvation configurations in the organic phase of lanthanum (La), europium (Eu), and lutetium (Lu) nitrate salts bound with a commonly used extractant, N,N'-dimethyl, N,N'-dioctylhexylethoxymalonamide (DMDOHEMA). The known lanthanide extraction trend of La ≈ Eu > Lu is readily explained by the measured free energy surfaces, which show consistent DMDOHEMA coordination from La to Eu, followed by loss of DMDOHEMA coordination from Eu to Lu. These simulations suggest how ligand crowding at the metal center can control selectivity, in this case resulting in the opposite extraction trend as observed with other conventional extractants, where the enthalpic contribution from increasing lanthanide charge density across the series dominates the extraction energetics. We also find that the presence of inner-sphere water, verified by time-resolved fluorescence, diversifies the accessible solvation structures. As a result, understanding solvation requires consideration of an entire thermodynamic ensemble, rather than the single dominant lowest-energy structure, as is often considered out of necessity in interpretation of spectroscopic data or in electronic structure-based ligand design approaches. In general, we demonstrate how metadynamics uniquely enables investigation of complex, multidimensional solvation energetic landscapes, and how it can explain selectivity trends where extraction is controlled by more complex mechanisms than simple charge density-based selectivity.

Spectroscopic characterization of europium binding to a calmodulin-EF4 hand peptide-polymer conjugate.

The emergence of biological ligand as an alternative to chemical ligands enables a sustainable lanthanide extraction route. In this study, a peptide originating from the loop of domain 4 calmodulin (EF4) was synthesized and the interaction with europium ions was monitored using time resolved laser fluorescence spectroscopy (TRLFS). Despite being retracted from its full protein structure, the twelve amino acids of calmodulin-EF4 showed binding to europium. Europium-peptide complex formation was evident by an increase in decay time from 110 to 187 μs. The spectra of europium bound to peptide can be easily distinguished from the free europium ion as the 5D0 → 7F2 peak intensifies. When europium bound to the peptide-polymer conjugate, the decay time was further increased to 259 μs. This suggests that lanthanide binding can be enhanced by immobilizing the short peptide into a polymer matrix. The europium-peptide/conjugate bond was reversible, triggered by pH, promoting peptide reusability. Due to the fact that the study was conducted exclusively in water, it suggests minimal use of chemicals is possible while maintaining peptide affinity. This makes the calmodulin-EF4 peptide an ideal candidate as biological ligand. This study lays the groundwork for developing a peptide-based filter material for lanthanide separation.

UNDERSTANDING THE ROLE OF DIFFUSION IN THE SEPARATION OF RARE EARTH ELEMENTS IN WATER-n-HEXANE SYSTEMS: A MOLECULAR DYNAMICS SIMULATION STUDY

Liquid-liquid extraction is one of the methods for separating rare earth elements (REE) in the presence of an extractant. The separation of REE ions, complex with an extractant, involves interfacial migrations that are influenced by the diffusion of the respective ions. Therefore, we performed molecular dynamics simulations on REE ions (La3+, Sm3+, Eu3+, Gd3+, and Tb3+) in a water-n-hexane system to determine if each ion exhibited a distinct diffusion coefficient. By employing molecular dynamics simulations, we calculated diffusion coefficients for these ions based on the Einstein relation. The diffusion coefficients for La3+, Sm3+, Eu3+, Gd3+, and Tb3+ were found to be 4.21×10–6, and 3.96×10–6, 4.57×10–6, 4.17×10–6, and 5.19×10–6 cm2/s, respectively. However, statistical analysis via the Kruskal-Wallis test revealed no significant variance in the diffusion coefficients (p-value greater than 0.05), indicating that diffusion is not a rate-limiting factor in REE separation. The findings suggest that effective mixing during extraction can eliminate the role of diffusion as a differentiating factor in REE separation. Overall, this study offers critical insights into optimizing REE extraction processes

Neutron Activation Analysis of Rare Earth Element Extraction from Solution through a Surfactant-Assisted Dispersion of Carbon Nanotubes.

We report the preparation of surfactant-assisted carbon nanotube dispersions using gum arabic, Triton X-100, and graphene oxide as dispersing agents for removing rare earth elements in an aqueous solution. The analytical tools, including (a) scanning electron microscopy and (b) neutron activation analysis, were utilized for qualitative and quantitative examinations, respectively. Neutron activation analysis was employed to quantitatively determine the percent of extraction of nuclides onto the carbon structure, while the images produced from the scanning electron microscope allowed the morphological structure of the surfactant-CNT complex to be analyzed. This report tested the effects responsible for nuclide removal onto CNTs, including the adsorbent to target mass ratio, the CNT concentration and manufacturing process, the pH, and the ionic radius. Observable trends in nuclide extraction were found for each parameter change, with the degree of dispersion displaying high dependency.

Strategic Minerals for Climate Change and the Energy Transition: The Mining Contribution of Colombia

To transition to carbon neutrality by the year 2050, copper, lithium, rare earths, cobalt, nickel, and silver are essential due to their use in the manufacture of electric cars, lithium batteries, wind turbines, solar panels, motors, and electrical wiring. The main goal of this study is to carry out a mining approach of the prospective areas of Colombia with strategic minerals for energy transition and climate change, analyzing the geospatial location, mining rights, mineral extraction, and royalty collection. Open data from SGC, ANM, and SIMCO geoportals were consulted. The prospective areas totaled 311,535.2 km2, equivalent to 27.3% of Colombia, and were located mainly in the Andes Mountains. The total area of mining rights and applications with strategic minerals for the energy transition is 112,802.2 km2 or 9.9% of Colombia, representing 5731 rights and 3939 applications. From 2012 to 2023, 448,330 tons of nickel, 172.9 tons of silver, and 171.6 tons of copper were mined in Colombia, which has contributed USD 513,140,286 as royalties to the state. No royalties have been earned from the extraction of rare earths, lithium, or cobalt. Fulfilling the Paris Agreement is possible with new sustainable mining projects of strategic minerals.

Generalized Pitzer-Debye-Hückel (PDH) Framework for the Deep Eutectic Solvent Assisted Extraction of Europium (III), Americium (III), and Uranium (VI)

ABSTRACT This study focuses on modeling of deep eutectic solvents (DESs) assisted liquid-liquid-extraction of Am(III), U(VI), Eu(III). In the present work, DESs are having tri – n octyl phosphine oxide (TOPO) and choline chloride acetate as hydrogen bond acceptor and malonic acid, oxalic acid and glycolic acid as hydrogen bond donor. The UNIQUAC-extended-PDH* model is used in the extraction formulation incorporating weak long-range interactions and short-range interactions. Metaheuristic algorithm, such as genetic algorithm, is employed for the determination of thermodynamically consistent binary interaction parameters using a pool of 40 tielines across six systems. The estimation of efficiency evaluation and extraction quantification contributes to a deeper understanding of the behavior of deep eutectic solvents in the extraction of lanthanides and actinides.

A study on speciation and enrichment of rare earth elements (REE) by sequential extraction from a potential coal fly ash resource and its role in REE extractability

Coal fly ash (CFA) is a potential secondary Rare Earth Element (REE) source that needs an efficient enrichment and extraction process. Annually, coal-fired power plants generate nearly 1 billion tonnes of coal ash. India alone produced 270.82 million tonnes of CFA in 2021–22. The average global concentration of REE in coal ash is 403.5 mg/kg. The present authors have already studied some promising CFAs from Indian thermal power stations and one such CFA is used in the present study for the sequential extraction (SE), speciation, and enrichment of REEs. Organic acids are used for SE to determine different fractions of REEs and it is found that REEs are mostly associated with amorphous Mn-oxide and organic and sulfide fractions. About 84% of REEs are in the glassy phase that SE cannot dissolve. The main components of CFA and SE residues are quartz, mullite, and glassy phase (52.0–59.2%). The XRF analysis showed that CFA is ‘Class F' (ASTM C618–19). The ESEM – EDS and backscatter imaging revealed monazite-(La) mineral as the REE carrier in CFA. Furthermore, enrichment studies using acid and alkali media have been performed. Alkali treatment with NaOH and KOH increased total REE by 1.61 and 1.32 times, respectively. Acidic treatment with HCl and oxalic acid increased total REE by 1.27 and 1.09 times, respectively. Therefore, NaOH followed by HCl treatment could be a cost-effective and sustainable REE enrichment and extraction method from CFA.

Extraction of actinides and lanthanides from nitric acid solutions with diphosphine dioxides in the presence of an ionic liquid

The e ect of 1-butyl-3-methylimidazolium bis[(tri uoromethyl)sulfonyl]imide ionic liquid on the extraction of lanthanides(III), U(VI), and Th(IV) from nitric acid solutions with 1,2-bis(diphenylphosphinyl)ethane I and 1,2-bis(diphenylphosphinyl)benzene II has been studied. The stoichiometry of the extractable complexes was determined. A solution of dioxide II in dichloroethane extracts metal ions much more e ciently than a solution of dioxide I. It has been established that, in the presence of an ionic liquid in the organic phase, the e ciency of extraction of metal ions from nitric acid solutions with solutions of dioxide I increases signi cantly, while that of dioxide II decreases. As a result, in the presence of an ionic liquid in the organic phase, dioxide II is signi cantly inferior to dioxide I in terms of the e ciency of extraction of Ln(III), U(VI), and Th(IV) from nitric acid solutions, which is associated with a much higher ability of dioxide II to extract HTf2N.

Extraction of actinides and lanthanides from nitric acid solutions with phosphorylated pyrazines

The extraction of U(VI), Th(IV), Am(III), and lanthanides(III) from nitric acid solutions with solutions of phosphorylated pyrazines in organic solvents has been studied. The stoichiometry of the extracted complexes was determined, and the in uence of the structure of the extractant and the concentration of HNO3 in the aqueous phase on the e ciency of the extraction of metal ions into the organic phase was considered. It has been established thatm among the studied compounds, bis(diphenylphosphine)quinoxaline dioxide has the highest extraction ability with respect to actinides and lanthanides in nitric acid media.