Separation Of Rare Earth Metals Research Articles

Investigation of the extraction of samarium and gadolinium from leaching solutions of phosphorus-containing raw materials using solid extractants

In accordance with the State Program of the Russian Federation «Development of Industry and Its Competitiveness», as well as the absence of balance deposits of rare earth metals on the territory of the Russian Federation, it is urgent to study methods for the extraction and separation of rare earth metals from technological solutions obtained during the processing of apatite concentrates. The article is devoted to the study of the kinetic features of solid-phase extraction of samarium (III) and gadolinium (III) from simulated industrial phosphoric acid solutions. Levextrel resine (co-polymerization product of styrene and divinylbenzene) containing Di-2-ethylhexylphosphoric acid (D2EHPA) – was used as a solid-phase extraction agent. Significant dependence of samarium (III) and gadolinium (III) extraction rate constant on the stirring rate was revealed using the formal first-order kinetic equation. Based on the linear dependences of the logarithm of the reaction rate constant on the reciprocal temperature, the activation energies for the extraction of Gd and Sm from phosphate model solutions were established, which, respectively, were 42.47 and 28.48 kJ/mol. The obtained values of the activation energies indicate that the limiting stage of the extraction process on a solid extractant can be considered a chemical reaction between ions of rare-earth metals and functional groups of the extractant. Separation of elements at the extraction stage is possible at temperature of 333 K under non-equilibrium conditions with separation coefficient up to 1.8 in 5 min.

On the Separation of Rare Earth Metals in the Cascade of Extraction Columns by Liquid–Liquid Chromatography Methods

On the Separation of Rare Earth Metals in the Cascade of Extraction Columns by Liquid–Liquid Chromatography Methods

Separation of rare earth metals in countercurrent extraction cascades using binary extractants

The use of binary extractants (BE) in schemes of countercurrent extraction cascades designed for the separation of rare earth metals (REMs) has been studied. It has been shown that the main difference between the use of BE and cation-exchange extracts (CE) is the possibility of using deionized water in the re-extraction cascades, rather than solutions of mineral acids. When optimizing the REM separation scheme, a mathematical model was used to dynamically calculate the distribution of separated metals over the stages of counterflow extraction cascades. The modeling of cascades was carried out on the basis of the physicochemical description previously obtained by the authors of the processes of extraction of REM nitrates with various BE compositions prepared on the basis of industrial cation- and anion-exchange extractants. Calculation of the balance of lanthanides during successive separation by stages of cascades was performed for the initial mixture of REM nitrates with the ratio of elements corresponding to the composition of the ore of the Chuktukonskoe rare metal deposit. A scheme of cascades is proposed for isolating in pure form the five REMs of light and light/medium groups (Pr, Nd, Sm, Eu, Gd) most demanded by the industry, concentrate of La, Ce, and concentrate of REM of medium/heavy and heavy groups. The scheme includes 10 countercurrent extraction cascades with a total number of extraction stages of 390. The scheme uses BE based on di-(2-ethylhexyl)phosphoric acid, synthetic fatty acids, tri-n-octylamine, and an industrial diluent. For the proposed scheme, mineral acid is used only at the stage of obtaining REM nitrates from the initial oxides; 1.8 kg (65%) of nitric acid is consumed per 1 kg of REM oxides. For the precipitation of REM carbonates from re-extracts, the consumption of sodium carbonate is approximately 1 kg per 1 kg of the initial REM oxides. The use of BE in comparison with CE makes it possible to significantly reduce the consumption of mineral acids and bases during the separation and production of individual REMs. The work was carried out within the framework of the state task of the Institute of Chemistry and Chemical Technology of the Siberian Branch of the Russian Academy of Sciences (project 0287-2021-0014) using the equipment of the Kranoyarsk Regional Center for Collective Use of the Federal Research Center of the KSC of the Siberian Branch of the Russian Academy of Sciences.

Sustainable composite material based on glutenin biopolymeric-clay for efficient separation of rare earth elements

Rare earth metals (REEs) are crucial for modern industries and technological development. Their extraction from non-renewable primary sources has almost reached its threshold due to excessive global demand. An effectual approach for REEs recovery is recycling secondary sources governed by separation materials. In this work, a novel glutenin-based Na-bentonite (Gle@Na_Bex:y) composite was produced via the in-situ hydrothermal route followed by a subsequent freeze-drying process. Additionally, a possible production route for the composites was proposed. The novel Gle@Na_Bex:y composites were characterized with Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) surface area, and zeta potential (ZP) measurements. FTIR results complemented with SEM images and XRD measurements confirmed the successful incorporation of glutenin into the Na-bentonite clay. The separation of REEs from aqueous solution was used as a model system to demonstrate the material’s ability for selective metal recovery. The best conditions (T, pH, time) for REE sorption were assessed using equilibrium batch adsorption experiments. The kinetics of REE adsorption were effectively explained by a pseudo-second-order model; all the adsorption equilibrium data followed the Langmuir model. Thermodynamic investigations revealed that the adsorption is endothermic and spontaneous, and the adsorption of REEs occurred through a chemisorption process. The sorption mechanism of REE ions was investigated using molecular modelling. The results of this study demonstrate the feasibility of utilizing Gle@Na_Be50:50 composite as an efficient material for REEs removal. The maximum adsorption capacities of Y3+, La3+, and Nd3+ achieved with Gle@Na_Be50:50, were 76.87, 56.71, and 74.61 mg/g, respectively. This work offers a new route for engineering, valuable composite materials for the separation of REEs from diverse sources.

The Effect of Surfactants on Separation of Light Rare Earth Metals using Emulsion Liquid Membrane Method: Review

Rare earth metals (REM) are scarce elements and are only found in the form of complex compounds of phosphate and carbonate. REM consists of 17 elements classified into light REM, medium REM, and heavy REM. This article is focused on lightweight REM, which is widely applied in various industrial fields. Many REM applications are increasing the demand for high-purity and bulk REMs. However, REM has almost the same physical and chemical properties, making it difficult to separate. Therefore, the separation of REM is interesting to study with various methods, one of which is Emulsion Liquid Membrane (ELM). ELM is developing a solvent extraction method involving three phases: the external phase, the internal phase, and the membrane phase. The key to the success of ELM lies in the stability of the emulsion, which is very dependent on the type and concentration of surfactants, so in the ELM process, it is necessary to choose the right concentration and type of surfactant. Therefore, this article was made to know the effect of surfactants such as span-80, span-85, and T154 in separating light REM using the ELM method.

Ionic Liquids Based on the Concept of Melting Point Lowering Due to Ethoxylation.

Most of the commonly used Ionic Liquids (ILs) contain bulky organic cations with suitable anions. With our COMPLET (Concept of Melting Point Lowering due to Ethoxylation), we follow a different approach. We use simple, low-toxic, cheap, and commercially available anions of the type Cx(EO)yCH2COO– to liquefy presumably any simple metal ion, independently of its charge. In the simplest case, the cation can be sodium or lithium, but synthesis of Ionic Liquids is also possible with cations of higher valences such as transition or rare earth metals. Anions with longer alkyl chains are surface active and form surface active ionic liquids (SAILs), which combine properties of ionic and nonionic surfactants at room temperature. They show significant structuring even in their pure state, i.e., in the absence of water or any other added solvent. This approach offers new application domains that go far beyond the common real or hypothetical use of classical Ionic Liquids. Possible applications include the separation of rare earth metals, the use as interesting media for metal catalysis, or the synthesis of completely new materials (for example, in analogy to metal organic frameworks).

Effect of Different Types of Extractants in the Separation of Rare Earth Metals using Emulsion Liquid Membrane Method: A Review

Rare Earth Metals (REMs) are minerals which needed in modern technology because it has unique chemical, catalytic, electrical and paramagnetic properties, so REMs have the potential to be applied in various fields. The similarity in the physical and chemical properties of REMs causes them to be difficult to separate from their parent minerals. Emulsion Liquid Membrane is an effective and efficient method for REMs purification and separation because in practice it only requires a small amount of solvent, the diffusion rate and mass transfer are high, fast, and simultaneous compared to the solvent extraction method which requires many extraction steps and requires a lot of solvents. In the emulsion liquid membrane method, one of the factors that can determine the success of the extraction process is the selectivity of the ligands/extractants. The extractants must be highly selective against the target REM ions, both in the external aqueous phase and the internal aqueous phase. Therefore, this review aimed to determine the selectivity of various types of extractants such as D2EHPA, Cyanex 302, Cyanex 572, (RO)2P(O)OPh-COOH, Aniline, and TBP on extraction efficiency and stripping efficiency in the separation of rare earth metals through the emulsion liquid membrane method.

Nonstationary separation of Nd and Pr by P507 extractant

The low efficiency of the separation of rare earth metals by extraction on one stage requires the combination of a large number of mixer-settlers in a cascade. The problem of increasing the rare earth elements separation factor is extremely urgent. One of the perspective methods is the nonequilibrium nonstationary process. In this work, it is offered to use the principle of a nonstationary extraction in the separation process of the Nd/Pr pair from chloride medium by the extractant based onP507. The results which have been received by an experimental setup allowing the monitoring of the influence of a cyclic change of physical-chemical parameters on extraction in the online modeare discussed. A comparison of two ways of implementation of extraction in the nonstationary mode is carried out. The apparent values of physical-chemical parameters (ΔG, ΔH, ΔS) in the temperatures range 15-65 °C are calculated from the data of joint extraction of Nd and Pr.

Tendencies in Application of Ionic Liquids and Binary Extractants in Extraction and Separation of Lanthanides and Actinides

Published data on the application of ionic liquids (ILs) and binary extractants in the extraction and separation of rare-earth metals (REMs) and radioactive elements, published in Russia and abroad during the last 5–10 years, are reviewed. An analysis of published studies demonstrated that new ILs used as solvents or additives to improve the extraction and separation of actinides and lanthanides are being presently developed. Difunctionalized and also binary extractants are widely used to separate REMs. Various extractive systems with ILs and factors affecting the efficiency of extraction and separation of actinides and lanthanides are considered and attention is given to the composition of compounds of the elements being extracted, selectivity of extractants, possibility of re-extracting metals from the organic phase, and practical use of ILs.

Separation of rare-earth metals and titanium in complex apatite concentrate processing

Intermediate processing products of apatite raw materials, such as the process solutions of phosphoric acid (PA) containing the in-demand rare-earth elements (REE) of heavy and medium-light groups, are a promising source of rare-earth metals. Apatite concentrate typically has low rare-earth metals grades (up to 1 %); therefore, sufficient economic value may only be achieved with those technologies that yield individual rare-earth metals without modifications in the underlying apatite raw materials process. Extraction methods have significant technological advantages, mainly due to the simplicity of implementation and the possibility of accelerated industrial-scale adaptation. Rare-earth metals recovery from PA process solutions into the organic phase based on di-2-ethylhexylphosphoric acid (D2EHPA) is associated with the simultaneous extraction of titanium (IV). Additional separation processes are, therefore, required in view of the presence of titanium in the REE extract. It has been found that effective titanium recovery from the organic phase is achieved by using oxalic acid with the concentration of 0.25 mol/l at the phase ratio of 0.5 and the mixing rate of 400 min–1. The content of impurity elements in the concentrates of individual REM compounds obtained of does not exceed 10–4 %. The complex processing operations performed for obtaining individual rare-earth metals represent a complete technology for the integrated processing of apatite raw materials. The work was carried out with the financial support of the Russian Science Foundation (project No. 19-19-00377).

Theoretical elucidation of rare earth extraction and separation by diglycolamides from crystal structures and DFT simulations

Diglycolamides (DGAs) show excellent application prospects for the extraction and separation of rare earth metals from highly radioactive liquid wastes and rare earth ores. The extraction ability of DGAs for rare earth ions in nitrate or chloride media increases with increasing atomic number of the rare earth metal. To understand the origin of this phenomenon, three binuclear crystals [Ln(TEDGA)3][Ln(NO3)6] of N,N,N′,N′-tetraethyldiglycolamide (TEDGA) with rare earth ions La(III), Pr(III) and Eu(III) were prepared and characterized crystallographically. The three complexes belong to the triclinic crystal system, P-1 space group. The bond lengths of Ln–Oamide are significantly shorter than those of Ln–Oether in the same crystal. The Ln–Oamide and Ln–Oether bond lengths gradually decrease with increasing atomic number of the rare earth ion. The dihedral angle formed by TEDGA and metal ions through the tridentate coordination gradually increases with increasing metal ion atomic number, tending toward the formation of sizeable planar coordination structures for the most massive rare earth ions. The structures of the compounds formed by the extractant and metal ion were optimized by means of DFT simulations. We find that the interaction between TEDGA and the rare earth ion is dominated by electrostatic interaction by analyzing binding energy, WBIs, Mulliken charge, natural electron configurations, and molecular orbital interaction. The covalent component of the Ln–O bonds of the complexes increases with increasing metal atomic number. The observed increase in extraction and separation capacity of diglycolamides for rare earth ions with increasing atomic number might be due to the formation of two five-member rings by one tridentate ligand. The rare earth ions with large atomic numbers tend to form planar structures with large dihedral angles with DGA ligands.

Solvent extraction of europium(III) from technogenic solutions with the use of surfactants

Objectives. The extraction and separation of rare-earth metals is a complicated process that requires a multidisciplinary and detailed investigation. Liquid-liquid extraction with the use of surfactant, along with the thermodynamic analysis of the parameters is considered a promising approach. The extraction and separation of rare-earth metals from low-concentration solutions represents an attractive research opportunity. The extraction of europium(III) from nitric acid solutions in the form of dodecyl sulfates has been experimentally studied. This work focuses on the study of fundamental and alternative sources of rare-earth metals and their extraction and separation.Methods. The extraction was performed on a top drive ES-8300 D equipment for 30 min at about 700 rpm. Infrared spectroscopy (Nicolet 6700 spectrometer) was used to determine the type of salts extracted into the organic phase. Extraction was studied in solutions with single cations and with a combination of the target element and interfering cations. For the latter, the concentrations of extracted elements in the aqueous phase were determined by optical emission spectroscopy with inductively coupled plasma on an ICPE-9000 (Shimadzu) spectrometer. The spectrometer was calibrated using standard samples for ICP CertiPUR (Merck).Results. The dependence of the distribution and separation coefficients of rare-earth metals during extraction on the pH value of the aqueous phase at equilibrium was investigated. Moreover, the form in which the elements are extracted was analyzed based on thermodynamic parameters. The minimum concentration of the target component in the aqueous phase was observed at pH 4.0. In general, the dependence of the distribution coefficient on the pH value of the medium is poorly expressed over the entire range of the pH range of the water phase. Based on the spectra of spent and pure isooctyl alcohol, it was concluded that europium dodecyl sulfates are extracted into the organic phase as Eu(C12H25OSO3) 3 solvates.Conclusions. The extraction of europium(III) from nitric acid solutions in the form of dodecyl sulfates was demonstrated. The advantages of the proposed method are the possibility of selective extraction of the target component from dilute solutions and the use of an easily available surfactant (sodium dodecyl sulfate). The efficiency of extraction of europium dodecyl sulfates was maximal in the pH range from 2.0 to 7.5, which reflects a weak dependence on the acidity of the aqueous phase. In addition, in the highly alkaline pH region, the extraction efficiency is reduced.

Calculation Studies of the Separation of Rare-Earth Metals by Countercurrent Liquid–Liquid Chromatography

Calculation studies have been made of the separation and concentration of rare-earth metals by countercurrent liquid–liquid chromatography with the semicontinuous loading of a sample into a chromatographic device using calculation software. This software is shown to be able to calculate chromatograms in steady- and unsteady-state modes for separating rare-earth metals and for concentrating one of the metals in the unsteady-state mode. By varying the number of steps, the sample loading time, and the durations of phase elution steps in each cycle, fractions with given purities of separated metals can be obtained.

Study on the extraction of lanthanides by a mesoporous MCM-41 silica impregnated with Cyanex 272

This work reports the synthesis of mesoporous silica impregnated by an acidic organophosphinic ligand (Cyanex 272) for the extraction of rare earth elements (REE). The prepared solid was characterized by X-ray diffraction (XRD), and N2 sorption at 77 K. The effect of pH, ligand loading, time and initial concentration on REE extraction were studied. Selectivity between light lanthanides (La), medium (Eu) and heavy lanthanides (Lu) followed the usual order Lu > Eu > La. The stoichiometry of the different species formed inside the porosity according to the conditions of the extraction (lanthanide nature and concentration; ligand loading) is proposed. The phosphinic ligand Cyanex 272 showed encouraging complexing properties in the porosity of the silica for its use in extraction and separation of rare earth metals.

Extraction Chromatographic Separation of Rare-Earth Metals in a Cascade of Centrifugal Extractors

Liquid–liquid chromatographic processes, in particular, separation of rare-earth metals, were proposed to be performed in a cascade of centrifugal mixer–settler extractors. Various modes of extraction chromatographic processes of rare-earth metal separation were theoretically analyzed.

Silica-based solvent impregnated adsorbents for separation of rare earth metals

ABSTRACTSilica-based solvent impregnated adsorbents are prepared, employing 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester as an extractant. Two kinds of silica particles are used as supports; (i) those whose surface is coated by a styrene/divinylbenzene copolymer and (ii) those whose hydroxyl-terminated pentadimethyl siloxane group is immobilized on the surface. The adsorbent based on silica particles coated by styrene/divinylbenzene can be repeatedly used for adsorption–elution processing, while the adsorption capacity of the adsorbent based on silica particles modified by the siloxane group is decreased by repeated cycles. The adsorbent is applicable to chromatographic operation for Dy/Nd, and quantitative adsorption–elution is achieved.

Synthesis of ion imprinted polymers for selective recognition and separation of rare earth metals

Lanthanide-ion imprinted polymers (L-IIPs) were synthesized by stoichiometric amounts of rare earth ions and the cavities in the polymers were created for the corresponding lanthanide ions. The maximum sorption capacities were estimated to be 125.3, 126.5, 127.6, 128.2 and 129.1 mg/g for Pr, Nd, Sm, Eu and Gd, respectively at pH 6. In the selectivity study, the L-IIPs exhibited good selectivity to the specific rare earth ions in the presence of coexisting cations. The imprinting results were found to be excellent with some rare earth ions over other competitor rare earth ions with the same charges and close ionic radius.

Comments on: Simultaneous Separation and Preconcentration of Rare Earth Elements on Activated Carbon for its Determination by ICP-OES in Beneficiation Products

Comments on simultaneous separation and preconcentration of rare earth elements on activated carbon/charcoal for its determination by ICP-OES in beneficiation products and different geological matrices has been presented. The manuscript published on benefication products is lacking in any innovation, originality or novelty over the earlier published paper titled “Determination of Rare earth elements in different geological matrices by ICP-AES after solid phase micro extraction on activated charcoal” by Murty, Mohanta and Radhamani published in the journal, Atomic Spectroscopy. There is a repetition of the “The unique feature of the method’ in the above cited manuscript and also in his earlier publication titled “A single stage simultaneous separation and preconcentration of rare earth elements on activated carbon for its determination by ICP-OES after wet ashing–application to soil samples by Chakrapani, Mahanta, Hanuman, Srivastava published in the journal “Exploration and Research for Atomic Minerals on bromoheavies. Moreover, there are contradictory and misleading statements /findings on the role of AC as adsorbent, amount of AC and desorption of REEs from AC in the published papers by Chakrapani et al. [1] and other authors from AMD laboratories. The findings have previously published elsewhere without proper cross referencing /justification in manuscripts. The desorption of REEs from AC simply by treating AC with 3.2 M HNO3 is the best analytical protocol, thus avoiding the tedious and time consuming operation of ashing AC. Moreover, regenerated AC can be re-used for further experiments. Dry-ashing of the charcoal pellet is the alternate option and can be completed in 1 hr. Wet-ashing of charcoal pellet with HNO3 and HClO4 involves toxic acids fuming, is a health hazard and may lead to serious explosions. Separation of rare earth metals through biosorption using low cost biomaterials or modified AC will continue to remain a greatest challenge.

Synthesis of a cross phosphonic acid type calix[4]arene with two different spacers and its extractive separation of rare earth metals

A phosphonic acid derivative of calix[4]arene in a cone configuration with two different alkylphosphonic acid substituents positioned at distal positions has been synthesized and used to investigate the extraction behavior towards rare earth metals. The new reagent exhibited both heavy rare earth metal extraction selectivity and very high extraction ability that is comparable to the separation efficiency of the commercial phosphonic acid extraction reagent, 2-ethylhexyl hydrogen 2-ethylhexylphosphonate, towards rare earth metals. The latter reagent is currently used as the most effective means for separating the rare earths. The high extraction and separation efficiency are largely attributed to the convergence of the functional groups in the above calix[4]arene derivative providing a preorganized metal binding site that reflects both the cyclic structure and the cone configuration of the calix[4]arene backbone. Any loss of “binding complementarity” due to the presence of different spacer groups connecting the two phosphonic acid groups to the calix[4]arene backbone is proposed to have been compensated by the operation of a chelate effect giving rise to high extraction ability being maintained. Extraction equilibrium constants and separation factors were estimated based on the extraction data. The stripping of the loaded rare earth metal ions with hydrochloric acid was also investigated.

Current State of the Rare Earth Industry in Russia and Siberia

The paper presents an evaluation of the rare earth industry in the former Soviet Union, Russia and the world. Main areas of use of rare earth metals, primary resources of rare earth metals are considered, forecast for the industry development is given. The conclusion about the prospects and opportunities of the organization of production and separation of rare earth metals at the Siberian Chemical Combine in the West Siberian region is made, and possible sources of raw materials for this production are analyzed.