Purification Of Rare Earth Elements Research Articles

A synthetic method for lanthanum hydroxychloride suitable for industrialization and its thermal decomposition properties.

A reactive crystallization method for the synthesis of lanthanum hydroxychloride (La(OH)2Cl) was developed to provide a new low-carbon route for the purification of rare earth elements in hydrometallurgy. The synthetic method reported herein represents a unique low-temperature route, short preparation time and inexpensive materials compared with previous methods, thus making it promising for industrial applications. The key factors controlling the product's phase were determined using single factor tests involving temperature, concentration of NH4Cl in the base solution and the molar ratio of NH4OH/La3+ added per minute into the base solution. Otherwise, the outcome is lanthanum hydroxide (La(OH)3). Subsequently, the synthesized products were characterized by employing X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and energy dispersive spectroscopy (EDS). Finally, the thermal decomposition behavior of La(OH)2Cl was assessed using thermogravimetry (TG) and differential scanning calorimetry (DSC). Lanthanum oxychloride (LaClO) was obtained at about 360 °C. The thermal transformation from LaClO to La2O3 started at 400 °C and was a slow oxidation process. Pure La2O3 could be obtained when the temperature increased to 1500 °C.

Separation and preconcentration of cerium (III) and Iron (III) on magnetic nanocomposite hydrogel

Iron is the most significant interfering metal ion during the purification of rare earth elements (REEs) from their mineral sources. Therefore, the current study aims to investigate the sorption behavior of the Ce3+ and Fe3+ ions using polyfunctional nanocomposite hydrogel (NCHG), as well as to provide foundational data for the development of the Ce3+ ions separation procedure. The adsorption capacity was tested in various aqueous media (chloride and sulfate media) to determine the optimal separation conditions for Ce3+ and Fe3+ ions. Numerous parameters, such as contact time, pH, and initial metal ion concentration, may impact the sorption process in batch mode. The results demonstrated that separation is more effective in an aqueous medium than in a chloride medium. In addition, their sorption is poor in sulfate medium, indicating that the prepared nanocomposite was selective in separating cerium from high-grade monazite (in chloride medium). With an adsorption uptake of up to 80% for Ce3+ in an aqueous medium, the synthesized nanocomposite was efficiently utilized for selective separation. The correlation coefficient (R2) of the Langmuir isotherm model was determined to be the highest and closest to 1. The experimental adsorption capacity of Ce3+ was reported at 151 mg/g. The adsorbed Ce3+ was desorbed efficiently from NCHG.

Terephthalaldehyde-Phenolic Resins as a Solid-Phase Extraction System for the Recovery of Rare-Earth Elements.

Rare-earth elements (REEs) are involved in most high technology devices and have become critical for many countries. The progress of processes for the extraction and recovery of REEs is therefore essential. Liquid–solid extraction methods are an attractive alternative to the conventional solvent extraction process used for the separation and/or purification of REEs. For this purpose, a solid-phase extraction system was investigated for the extraction and valorization of REEs. Ion-exchange resins were synthesized involving the condensation of terephthalaldehyde with resorcinol under alkaline conditions. The terephthalaldehyde, which is a non-hazardous aromatic dialdehyde, was used as an alternative to formaldehyde that is toxic and traditionally involved to prepare phenolic ion-exchange resins. The resulting formaldehyde-free resole-type phenolic resins were characterized and their ion-exchange capacity was investigated in regard to the extraction of rare-earth elements. We herein present a promising formaldehyde and phenol-free as a potential candidate for solid–liquid extraction REE with a capacity higher than 50 mg/g and the possibility to back-extract the REEs by a striping step using a 2 M HNO3 solution.

Parametric study and speciation analysis of rare earth precipitation using oxalic acid in a chloride solution system

Oxalic acid precipitation is a common step in the purification of rare earth elements (REE) from a concentrated pregnant leach solution (PLS). However, the presence of contaminants such as Al, Fe, and Ca in given amounts decreases the REE precipitation efficiency and product purity while also increasing the amount of oxalic acid needed to maximize recovery. As such, a statistically designed test program was performed to identify the optimal conditions necessary for a relatively low REE content PLS containing elevated concentrations of contaminant ions. The performance objective was maximization of REE precipitation efficiency while minimizing the oxalic acid dosage. A central composite design was utilized to quantify performance impacts and identify the ultimate set of parameter values for oxalic acid dosage, Fe(III) contamination concentration, solution pH, and reaction temperature. The resultant model suggested that oxalic acid dosage and reaction pH are the most significant factors for the REE precipitation efficiency, followed by the interaction of oxalic dosage and Fe concentration. Test results indicate that increasing the oxalic acid concentration from 0 g/L to 80 g/L improved the REE precipitation efficiency from approximately 4.2% to 95.0%. Furthermore, raising the solution pH from 0.5 to 2.5 considerably enhanced the precipitation efficiency from 0.0% to 98.9%. A solution temperature elevation decreased REE recovery, which indicated an exothermic reaction between REEs and oxalate anions. Finally, a high level of Fe contamination adversely impacted REE precipitation efficiency. To further the understanding of the REE-oxalate system, a fundamental solution chemistry study was performed using the equilibrium constants of the reactions. The study resulted in the development of oxalate speciation diagrams and provided an analysis of the REE precipitation characteristics at various oxalate anion concentrations and Fe(III) contamination levels using MINTEQ software. The dominant Fe(III) species in the solution system were found to be Fe-(C2O4)33-, Fe-(C2O4)2-, and Fe-(C2O4)+, which consume the majority of the oxalate anions. The simulated model was found to be in agreement with the experimental findings and helped to explain the adverse impact of increased iron concentrations on REE precipitation efficiency.

Extraction behavior of yttrium with Aliquat336 from nitrate and thiocyanate media: A microscopic view from computational analysis

Separation and purification of rare earth elements (REEs) from each other has been a challenging task and a topic of immense interest across the world. The separation of high purity yttrium from chemically similar heavy rare earths (HREs) could be possible due to its differential behavior in thiocyanate & nitrate media with quaternary amine type of extractant Aliquat336. In case of a hard donor like nitrate ion, Y behaves like heavy rare earths (HERs), more or less in accordance with its ionic radii. On the contrary, in thiocyanate medium, the extraction properties of Y follows the light rare earths (LREs) which makes its separation from Er and other HREs effective. In the present investigation, a microscopic analysis employing computational tools has been utilized to offer an explanation for this curious behaviour of yttrium. The computational results bring out the striking fact that while the behavior of Y remains unchanged in two mediums, it is the trend within the lanthanide series that changes between the two mediums. It is observed that the size of the REE nitrates follow a decreasing trend along the lanthanide series, where Y nitrate shows comparable bond lengths with Er nitrate. On the other hand REE thiocyanates follow an increasing trend in size, where Y thiocyanate bond lengths are closer to the La thiocyanate. Similar trend is observed for the partial charges on the outer atoms of REE nitrates and thiocyanates, which affects the electrostatic binding interaction with the extractant Aliquat336. The contrasting trend among the lanthanide series is further explained in terms of spin density analysis shows that, in case of a hard donor like nitrate, f-electron delocalization takes place into the ligand and the size of the REE nitrates follow the lanthanide contraction. Y in this case behaves like HREs. On the contrary, in thiocyanate medium there is no delocalization of f-orbital in inner-sphere thiocyanate complex and due to absence of f orbital in Y, it occupies position with light rare earths as extraction follows the trend of electrostatic attraction between cation and ligand. Understanding of this extractant interaction is expected to provide a knowledge based approach for the development of new extractant molecules with better binding capacity for specific REE of interest.

Graphene Oxide Caged Biopolymer Nanocomposite for Purification of Rare Earth Elements from High Grade Egyptian Monazite Concentrate

Graphene Oxide Caged Biopolymer Nanocomposite for Purification of Rare Earth Elements from High Grade Egyptian Monazite Concentrate

Revaluating solvent extraction equilibria of trivalent rare earths with EHEHPA (PC-88A) using Alstad equation

The equilibria associated with the solvent extraction of trivalent rare earth elements (REEs) with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHEHPA) have been previously studied by many researchers because of the industrial importance of REEs. However, quantitative analysis has been limited to relatively low concentrations of EHEHPA because of the nonideal characteristics of the organic phase. In the present paper, we used an empirical equation to correct the nonideality of the organic phase and calculated extraction equilibrium constants for some trivalent REEs (La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, and Y) that are particularly important in RE recycling from end-of-life products and in-plant scraps. Calculations based on use of EHEHPA in a nonpolar diluent and a nitrate medium were used to systematically investigate equilibria at a constant ionic strength of 1 mol/L, temperature of 298 K, EHEHPA dimeric concentrations that ranged from 0.04 to 0.33 mol/L, and a range of pHs. Apparent extraction equilibrium constants that reproduced the distribution ratios of the REEs with good accuracy were obtained. Further experiments at higher EHEHPA concentrations revealed that the empirical equation was effective up to an EHEHPA dimer concentration of 0.5 mol/L, which is significantly higher than the upper bound for the conventional dimer model. Separation factors defined as the ratios of the distribution ratios of two REEs were calculated from the extraction equilibrium constants for the possible pairs of REEs and compared critically with literature values. Differences in the separation factors depended on the measurement conditions and were most pronounced when the difference in atomic numbers of the REEs was large. The results are expected to facilitate designing processes for the separation and purification of REEs.

Recovery and purification of rare earth elements from wastewater and sludge using a porous magnetic composite of β-cyclodextrin and silica doped with PC88A

Global mining of rare earth elements (REEs) has increased exponentially because of their modern technologies' applications. The recovery of REEs from secondary sources such as industrial wastewater and industrial sludge can reduce the radioactive wastes and greenhouse gases generated during their mining and processing, as well as numerous environmental pollutions from REEs commercial products. In this work, β-cyclodextrin hybrid (P-CDP@Fe3O4) was functionalized with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl (PC88A) doped in silica. The synthesized composite, namely PCDP-M-SHM, performed better toward recovering REEs. The quantitative desorption of adsorbed REEs using dilute acidic solutions was achieved over five cycles without degradation in composite performance. More importantly, PCDP-M-SHM was found to selectively purify REEs from synthetic solutions and industrial wastewater in a continuous adsorption process with enrichment factors ranging from 10 to 30. Finally, the separation factor confirmed the effectiveness of PCDP-M-SHM to recover REEs from digested sludge with much higher distribution coefficients than coexisting elements. These results indicate that the synthesized adsorbent is a promising solution for REEs separation and purification from water.

Quantitative Structure-Property Relationship (QSPR) Study on the Complex Compounds Formed From Gadolinium(III) with Dibutyl Dithiophosphate Derivatives Ligands Based on Molecular Descriptors

A study of the quantitative relationship of structure and property (Quantitative Structure Property Relationship (QSPR) has been carried out on complex compounds formed between gadolinium (Gd) and dibutyldithiophosphate (DBDTP) derivative ligands. This study is a part of our laboratory research program on the development of extractant ligands, including DBDTP in extraction for the separation and purification of rare-earth elements (REEs), specifically Gd. Gadolinium has also been a part of the research program about its use in the synthesis of magnetic resonance imaging (MRI) contrast agents, for the diagnosis of various diseases. This chemical calculation research aims to analyze the effect of descriptors in the form of parameters of the physical-chemical properties of bond lengths, bond angles, and bond energies on the stability of Gd complex compounds with DBDTP derivative ligands. To get descriptors PM7 semi-empirical method was used, while for data analysis, Multiple Linear Regression Analysis was used, assuming the model error is normally distributed with zero mean and constant variance. Furthermore, data processing was done using SPSS software. This research was conducted by involving 28 DBDTP derivative ligands and using multiple linear regression analysis. The regression equation is Y ̂ = - 0.966 + 0.586 V1 - 0.014 V2 + 0.000 V3. From the resulted research data it was found that there are three findings, namely: (1) bond length and bond angle have a significant simultaneous effect on stability of Gd complex compounds with DBDTP derivative ligands; (2) bond length and bond angle have a partially significant effect on stability of Gd complex compounds with DBDTP derivative ligands; (3) bond length proved to have a significant dominant effect on stability of Gd complex compounds with DBDTP derivative ligands.

Study on the Effect and Mechanism of Impurity Aluminum on the Solvent Extraction of Rare Earth Elements (Nd, Pr, La) by P204-P350 in Chloride Solution

Solvent extraction is the most widely used method for separation and purification of rare earth elements, and organic extractants such as di(2-ethylhexyl) phosphoric acid (P204) and di(1-methyl-heptyl) methyl phosphonate (P350) are most commonly used for industrial applications. However, the presence of impurity ions in the feed liquid during extraction can easily emulsify the extractant and affect the quality of rare earth products. Aluminum ion is the most common impurity ion in the feed liquid, and it is an important cause of emulsification of the extractant. In this study, the influence of aluminum ion was investigated on the extraction of light rare earth elements by the P204-P350 system in hydrochloric acid medium. The results show that Al3+ competes with light rare earths in the extraction process, reducing the overall extraction rate. In addition, the Al3+ stripping rate is low and there is continuous accumulation of Al3+ in the organic phase during the stripping process, affecting the extraction efficiency and even causing emulsification. The slope method and infrared detection were utilized to explore the formation of an extraction compound of Al3+ and the extractant P204-P350 that entered the organic phase as AlCl[(HA)2]2P350(o).

Nitrogen-doped nanoporous graphene induced by a multiple confinement strategy for membrane separation of rare earth.

SummaryRare earth separation is still a major challenge in membrane science. Nitrogen-doped nanoporous graphene (NDNG) is a promising material for membrane separation, but it has not yet been tested for rare earth separation, and it is limited by multi-complex synthesis. Herein, we developed a one-step, facile, and scalable approach to synthesize NDNG with tunable pore size and controlled nitrogen content using confinement combustion. Nanoporous hydrotalcite from Zn(NO3)2 is formed between layers of graphene oxide (GO) absorbed with phenylalanine via confinement growth, thus preparing the sandwich hydrotalcite/phenylalanine/GO composites. Subsequently, area-confinement combustion of hydrotalcite nanopores is used to etch graphene nanopores, and the hydrotalcite interlayer as a closed flat nanoreactor induces two-dimensional space confinement doping of planar nitrogen into graphene. The membrane prepared by NDNG achieves separation of Sc3+ from the other rare earth ions with excellent selectivity (∼3.7) through selective electrostatic interactions of pyrrolic-N, and separation selectivity of ∼1.7 for Tm3+/Sm3+.

Foam flotation of rare earth elements by conventional and green surfactants

Foam (ion and precipitate) flotation is a promising green method of recovery of rare earth elements (REE) from leachates of the primary and secondary resources. However, the capabilities of foam flotation in solutions simulating real leachates are currently poorly understood, especially for green surfactants as collectors. In this work, we report the results of foam flotation of La(III), Ce(III), Gd(III), and Yb(III) ions individually, as a group, and as a group with gangue ions (Al(III), Zn(II), Ca(II), and Mg(II)). These REE represent both light and heavy REE. As the collectors, we test two quintessential synthetic and green anionic surfactants—sodium dodecyl sulfate (SDS) and mono-rhamnolipid, respectively. We find that the floatability of REE with SDS depends considerably on the composition of the REE solution and demonstrate that the recovery kinetics can be used as additional control of the REE separation in the group flotation with gangue ions. Another important finding is that mono-rhamnolipid at a concentration as low as 10 μM can recover up to 100% REE in the group flotation against gangues, except for Al(III) and Zn(II). At pH 9, mono-rhamnolipid selectively removes REE in the group flotation with gangue cations at a surfactant:total cation (excluding Na+) ratio as low as 1:13. We offer an interpretation of the effects observed. Overall, our results demonstrate that foam flotation is capable of selectively recovering an individual REE from a mixture of several REE with gangue ions, provided that the flotation conditions such as surfactant structure, surfactant concentration, solution pH, and flotation time are properly selected. These results are an important milestone toward the commercialization of foam flotation for the recovery and purification of REE.

New Mathematical Formulation for the Deposition Potential and Atomic Radius: Theoretical Background and Applications to Sn–Ln Intermetallic Compounds

Purification of rare earth elements is challenging due to their chemical similarities. The interaction and behavior of alloys involving stannous chloride (SnCl2) and lanthanide metals are discussed in the present paper. We investigate the quantitative relationship between the deposition potential of lanthanides with SnCl2 and atomic radius by employing electrochemical techniques, involving cyclic voltammetry (CV), square wave voltammetry (SWV) and open-circuit chronopotentiometry (OCP). Our electrochemical study on the formation intermetallic compounds is based on Sn in LiCl–KCl melts on molybdenum electrodes at 873 K. With the same experimental conditions, different deposits (e.g., Sn–La, Sn–Pr, Sn–Gd, Sn–Dy and Sn–Er) were obtained by using identical substrates. We establish the relationship between the deposition potential and the atomic radii of lanthanides by deriving a mathematical equation from the sorting out and summarizing of the data. The predictions for the existence and the deposition potenti...

Electro‐kinetic Separation of Rare Earth Elements Using a Redox‐Active Ligand

Purification of rare earth elements is challenging due to their chemical similarities. All of the deployed separation methods rely on thermodynamic properties, such as distribution equilibria in solvent extraction. Rare-earth-metal separations based on kinetic differences have not been examined. Herein, we demonstrate a new approach for rare-earth-element separations by exploiting differences in the oxidation rates within a series of rare earth compounds containing the redox-active ligand [{2-(tBuN(O))C6 H4 CH2 }3 N]3- . Using this method, a single-step separation factor up to 261 was obtained for the separation of a 50:50 yttrium-lutetium mixture.

Red mud as secondary source for critical raw materials – purification of rare earth elements by liquid/liquid extraction

AbstractBACKGROUNDCritical raw materials (CRM) are crucial to Europe's economy and essential to maintaining and improving our quality of life due to their usage for production of many devices. Red mud is generated from alumina production where bauxite is digested in hot sodium hydroxide solution during the Bayer process. Red mud can contain considerable amounts of CRM such as rare earth elements (REEs). In the present study, purification of CRM from perturbing, co‐extracted elements such as Fe and Al from red mud hydrochloric acid leachates was evaluated.RESULTSA first purification was achieved by removing Fe (>87%) from the acidic leachate using precipitation with NaOH. REEs as well as Al were hardly removed by precipitation (21%, and 33%, resp.). A second purification was achieved using liquid/liquid extraction (LLE) with di‐(2‐ethylhexyl)phosphoric acid (D2EHPA). Here, four explanatory variables (i.e. LLE organic/aqueous ratio, D2EHPA concentration in kerosene, stripping acid organic/aqueous ratio, HCl concentration) were studied. Finally, the optimal extraction conditions maximizing the economic potential (total metal extracted × economic value of the respective metal) of CRM were determined using a design of experiment approach.CONCLUSIONThe experimentally determined economic potential extracted corresponded well to the prediction (88%; to the predictions, maximum recovery of 17.18 ± 0.59 US $ t−1). Ultimately, more than 40% of the overall REEs (>62% of the leachable REEs) in red mud were purified using LLE, whereas Al was successfully rejected from the concentrate (∼5% of the overall Al present). © 2017 Society of Chemical Industry

Sorption from slurries—A promising method in the processing of rare earth elements

The article presents the results of sorptive extraction of rare-earth elements (REE) from the solutions and slurries of complex salt compositions using sulfocationites and carboxyl cationites with a predominant content of the latter on laboratory and pilot scales. Upon REE sorption from hydrate slurry on KM-2p carboxyl cationite, the REE extraction rate of at least 98% has been achieved, and the following factors of ΣREE purification from impurities have been obtained: KREE/Al = 1.7, KREE/Th = 2.3, KREE/Ca ≈ 20, KREE/Zr = 15, KREE/Fe ≈ 40, and KREE/P,F ≈ 90. It is demonstrated that the REE capacity of cationite SG-1m is higher than that of cationite KM-2p by 10%; moreover, the content of thorium on KM-2p cationite is lower by 2.5 times and that of zirconium by 6 times. After the recovery of saturated cationites by 1.5–2.0 M HNO3 solutions, strippants have been extracted with a REE concentration of 15–20 g/L. The factors of REE purification from impurities upon desorption are as follows: KREE/Al = 2.5, KREE/Th = 0.5, KREE/Ca = 5.3, KREE/Zr = 5.6, and KREE/Fe = 0.8. The REE recovery rate is ≥99%.

Separation and Manipulation of Rare-earth Oxide Particles by Dielectrophoresis

A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis (DEP) microchip of microelectrode arrays. This microchip device is constructed in order to use DEP to capture micro-particles of rare-earth oxides in petroleum. Dielectrophoretic behavior of micro-particles of rare-earth oxides in oil media is explored. The dielectrophoretic effects of particles under different conditions are investigated. It is showed that the prepared microchip is suitable for use in the investigation of dielectrophoretic responses of the rare-earth oxides in oil media. The factors such as frequency, particle size and valence of rare-earth metal are discussed. When the frequency is fixed, the translation voltage decreases as particle size increases. Lower frequencies are more effective for manipulation of inorganic particles in oil media. Particles of the same rare-earth oxide with different size, as well as particles of different rare-earth oxides, are captured in different regions of the field by regulating DEP conditions. This may be a new method for separation and purification of particles of different rare-earth oxides, as well as classification of particles with different size.

Purification of rare earth elements from monazite sulphuric acid leach liquor and the production of high-purity ceric oxide

The present work describes the development of an efficient and relatively simple process to obtain high grade CeO 2 from sulphuric acid leach liquor. The liquor was obtained through acid digestion of monazite. The steps investigated in the process for obtaining ceric oxide were: (i) purification of the RE elements through their precipitation as rare earth and sodium double sulphate (NaRE(SO 4) 2· xH 2O), (ii) NaRE(SO 4) 2· xH 2O conversion into RE-hydroxide (RE(OH) 3) through metathetic reaction and (iii) recovery of cerium and (iv) purification of cerium from the mixture of ceric hydroxide and manganese dioxide precipitate through dissolution of the solid with HCl and precipitation of the cerium through the addition of oxalic acid (H 2C 2O 4) or ammonium hydroxide (NH 4OH) solution. The X-ray diffraction spectra of the double sulphate obtained indicated the presence of monohydrated double sulphate. X-ray diffraction and chemical analysis indicated that the precipitation should be carried out at 70 °C and at 1.1 times the stoichiometric ratio of NaOH. An excess of 30% of KMnO 4 was necessary to separate cerium from the other RE elements. Both oxalic acid and ammonium hydroxide proved efficient in the precipitation of cerium from the mixture of Ce/Mn obtained in the cerium separation. Following purification, calcinated products were obtained, assaying between 99% and 99.5% CeO 2. The cerium recovery yield was greater than 98%.

Preparation and characterization of carbamoylphosphonate(CMPO) silane grafted on various mesoporous silicas

The carbamoylphosphosphonate silane (CMPO analogue; 2-(diphenylphosphoryl)-N-(3-(triethoxysilyl)propyl) acetamide) modified mesoporous silica was prepared via a post-synthesis grafting method for the effective purification of rare earth elements. The guest CMPO analogue was synthesized by direct coupling reaction of 2-(diphenylphosphoryl) acetic acid and 3-(triethoxysilyl)propan-1-amine. Various mesoporous silicates such as MCM-41, SBA-15, or amorphous silica nanoparticles were adopted as host materials. The resulting surface-modified mesoporous materials were characterized with respect to their structural integrity, surface area, and pore size and the concentration of the CMPO silane species. These CMPO functionalized periodic mesostructured silicates offer the potential of applications as catalysts, sensors, or environmental sorbents.

Studies of the Effect of Crosslinking in the Strongly Basic Anion Exchanger Dowex 1 and the HNO3 Concentration Employed on the Separation of the SmIII–NdIII Pair in the Polar Organic Solvent–H2O–HNO3 System

Because of their specific structure, rare earth elements are used for the modification or structural stabilization of many metallic or ceramic materials employed in modern technology and also in the metallic form, i.e. in alloys and compounds with unique properties. Industrial demand for rare earth metals has increased lately due to their new application possibilities, e.g. in supermagnets of the Nd–Fe–B type or in ceramic high-temperature superconductors. Equally, the application of rare earth elements in metallurgy, catalysis, ceramics, etc. remains of significant importance. The separation and purification of rare earth elements(III) which occur in groups with similar physicochemical properties involve extremely difficult and complex processes. Ion exchange is one method which enables such separation. This paper presents the results of studies of the influence of the extent of crosslinking in the anion exchanger Dowex 1 and the concentration of nitric acid on the separation of the SmIII–NdIII pair by frontal analysis in 90% v/v CH3COCH3– or the CH3OH–10% v/v × M HNO3 systems. The most effective results were obtained in the 90% v/v CH3OH–10% v/v 7 M HNO3 system employing the anion exchanger Dowex 1 × 4 allowing 0.11 kg samarium(III) to be purified on 1 dm3 ion exchanger in the nitrate form and leading to a decrease in the micro-component content to a value below 10−3%.