Concentrations Of Rare Earth Metals Research Articles

POSSIBILIITY OF URANIUM EXTRACTION FROM SPENT NUCLEAR FUEL IN FUSED ELECTROLITES CONTAINING RARE ELEMENTS

Link for citation: Nikitin D.I., Polovov I.B., Rebrin O.I. Possibility of uranium extraction from spent nuclear fuel in fused electrolytes containing rare elements . Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 10, рр. 210-218. In Rus. The relevance of the research is caused by the plans of using electrolytic separation of metalized spent nuclear fuel as a stage in pyrochemical reprocessing of mixed nitride uranium-plutonium fuel. The main aim is to determine the parameters of uranium electrolytic separation from an alloy with simulators of fission products (precious metals and rare earth elements) simulating spent nuclear fuel in salt mixtures based on 3LiCl–2KCl with additives of rare earth element chlorides. Objects: model spent nuclear fuel – uranium alloy with simulators of fission product (precious metals and rare earth elements) with a mass compound of Pd:Ru:Ag:Rh=25:1:3:3, Nd:Ce:La:Pr:Sm:Y=15:10:5:5:5:1). Methods: electrorefining, X-ray fluorescence and X-ray diffraction method of analysis, inductively coupled plasma mass spectrometry, assessment of distribution of components in the system. Results. The data obtained showed that uranium deposits have dendrite formations of alpha-uranium at 550 °C in orthorhombic crystal system toward needle cathode current density. The resulting cathode deposits are free from impurities of ruthenium, rhodium, molybdenum, praseodymium and yttrium. The purification coefficient for palladium reaches 3000, and for silver 1700. Noble metals accumulate in the anode sludge, and even with the complete depletion of the anode material. The concentration of noble metals in the cathode deposit does not exceed 0,0015 wt %. Despite the high concentration of rare-earth chlorides in the electrolyte, which simulates the accumulation of rare-earth ions during repeated reprocessing of spent nuclear fuel, the concentration of rare-earth metals in the cathode product did not exceed 0,007 wt %. During uranium electrowinning from a model spent nuclear fuel in the 3LiCl–2KCl–UCl3 electrolyte (10,1 wt %) with REE chlorides, which imitate their accumulation in the electrolyte during repeated processing, at 550 °C, as well as the initial cathode current density of 0,2 A/cm2, the specific amount of electricity is 1,0 A∙h/cm2. A cathode uranium deposit is released with a current efficiency exceeding 90 % with all anode mass depletion, and purification coefficient 1800 for the sum of precious metals and for the sum of rare earth metals.

Principles of rational processing of red mud with the use of carboxylic acids

Due to the known limitations of economic nature, the global production complex continues to focus on the most accessible technologies of alumina production, leading to the accumulation of solid waste (red mud), which has created the well-known problem of their processing, and its scale and importance continue to grow in connection with the steady increase in the world volume of aluminum production and consumption. The priority of rational use of natural resources allows us to speak about the preference of principles of deep and waste-free processing of mineral raw materials, which are fully applicable to the processing of red mud, as accumulated raw materials of technogenic origin. At the same time, the key point of this approach becomes the hierarchical division of components into groups of technological products, taking into account the processes that ensure this selective-group division. In this regard, the use of carboxylic acids is of notable interest, as they have a known selectivity to the main components of red mud, which allows to separate low-soluble components (iron and silicon compounds) from light and rare-earth metals with minimum consumption rates. An experimental study has shown that flow-through leaching of thermochemically prepared red mud using formic acid provides high and acceptable recoveries of sodium, calcium, scandium, and rare earth metals. This makes it affordable to use the cheapest method of apparatus-free leaching when implementing this approach on an industrial scale. Experimentally determined the differences in the sequence of elution of sodium, calcium, aluminum and rare-earth metals formates during flow leaching, which creates favorable conditions for concentrating components and separate processing of sampled solutions. The regime parameters of the process that provides complete precipitation of aluminum, scandium and rare earth metals during the neutralization of formate solution with milk of lime, resulting in the necessary prerequisites for further concentration of rare earth metals to obtain technologically significant product are determined. The work was carried out with the financial support of the Russian Science Foundation under the Agreement No. 18-19-00577-П of April 28 2021 of grant for fundamental scientific research and exploratory scientific research.

Study of rare earth elements in the coals of the Shubarkol deposit

The work studies mineralogical and geochemical features of the Jurassic coals of the Shubarkol deposit. The samples were examined using the method of scanning electron microscopy (SEM-EDX) Hitachi S-3400N, which was carried out at the Uranium Geology Research and Development Center at the Department of Geoecology and Geochemistry of TPU. Coal geochemistry was studied by instrumental neutron activation analysis (INAA) at the nuclear geochemical laboratory of the Department of Geoecology and Geochemistry of National Research Tomsk Polytechnic University (TPU). The choice of this object of study was determined by the tasks of research including the study of the patterns of accumulation of abnormal concentrations of REE, the effect of various factors of the geological environment on the levels of their accumulation in coals, as well as the conditions of its concentration and forms of occurrence in coals to expand the mineral resource base of Kazakhstan for rare earth elements. According to the results of scanning microscopic analysis, aluminosilicates, sulfides and sulfates with inclusions of microparticles of rare and rare earth elements were found in the composition of the Shubarkol deposit coals. According to the INNA results, abnormal concentrations of Sc, Ta, Nb, Hf, Zr, Ba, Sr, Ce and REE were found. Weathering processes led mainly to the loss and redistribution of REE in the coal seams of the Shubarkol deposit, which in turn led to increasing the content of rare earth elements from the bottom up the section. As a result of the action of multiple processes, increased concentrations of rare earth metals, mainly of the yttrium group, were formed. The absence of negative europium anomaly was determined, which confirms the original rocks composition peculiarity. The maximum contents of rare-earth metals are confined to weathered coals; for the medium-heavy group (Nd, PM, Sm, Eu), they are almost a hundredfold higher than the clarke in the upper continental crust. The tenfold excess of the clarke for elements from Gd to Lu was found in clayey sandstones and siltstones; for the rest of the rocks of the deposit the excess over the clarke is significantly lower. It was found that the coals of the deposit belong to the H-type and L-type of REE distribution. During the formation of oxidized H-type coals, clayey matter of terrigenous ash predominated as a carrier of REE, while unoxidized L-type coals were formed with the introduction of REE into the coal accumulation basin mainly in the composition of clay minerals and LREE-phosphates. Here the main source of REE was apparently the weathering crust over acidic rocks.

The distribution coefficients of Y3+ and Eu3+ between HNO3 and HDEHP

The recovery and purification of rare earth metals from electronic waste is an attractive alternative to environmentally damaging virgin mining of these metals, as the concentrations of rare earth metals are significantly higher in electronic waste than can be found naturally. It is therefore prudent to develop recycling and purification processes for these metals from electronic waste. Solvent extraction is the most commonly used technique for the purification of rare earth metals, as solvent extraction is capable of handling large volumes while maintaining high product purities. Since there is a scarcity of thermodynamic phase equilibrium data that can assist in developing such recycling processes, this study begins a series of investigations to address this gap.The distribution coefficients of Y3+ and Eu3+ ions between an organic phase and an aqueous nitric acid solution, as a function of the nitric acid concentration, were measured at approximately 298 K. These are reported for systems containing an organic phase of di-(2-ethylhexyl) phosphoric acid (HDEHP) in a diluent; varying either the diluent or the concentration of the HDEHP. The two diluents investigated were n-nonane and n-dodecane. Measurements were conducted in a liquid-liquid equilibrium cell, with the concentration of the rare earth metals determined by ICP-OES analysis. The distribution coefficients for Y3+ and Eu3+ were shown to be inversely proportional to the aqueous acid concentration, and dependent upon both the concentration of the HDEHP in the organic phase and the diluent used. The data were used for the optimisation of a rare earth metal extraction column.

Presence of other rare earth metals in gadolinium-based contrast agents

Gadolinium-based contrast agents (GBCA) are widely used to enhance tissue contrast during magnetic resonance imaging (MRI) procedures. However, free Gadolinium (Gd) is undesirable as a drug substance, due to its high toxicity. Consequently, a coordinating ligand is required to keep it in solution and to increase tolerance. In order to achieve an adequate performance, GBCA must be administered in relatively large amounts. Chelate amounts are around 13–20 g and for Gd alone, this may amount to 3.3 g. Taking into account the route of administration, impurities in GBCA may be significant. Gadolinium occurs in nature along with 16 other elements known collectively as rare earth metals (RE), which are found throughout the earth's crust in minerals such as monazite. Gadolinium oxide corresponds to 0.7–4.0% of the RE present in minerals, and the sum concentration of RE in minerals is around 4%. Rare earth metals are difficult to separate, as the chemical and physical properties of one RE are significantly similar to those of others. In this study, the presence of other RE in GBCA formulations was investigated. Different lots of Magnevist®, Viewgam®, OptiMARK®, Omniscan®, Dotarem®, and Gadovist® were analyzed. Inductively-coupled plasma mass spectrometry and atomic absorption spectrometry were used for RE determination. Procedure optimization included sample decomposition and method validation for element determination. The results showed that Sc, Y, La, Ce, Pr, Nd, Eu, Tb, Tm, Dy, Ho, and Er were present in the 22 samples analyzed. Terbium, Thulium, Europium, and Lanthanum were, on average, found in the highest amounts, which were 0.42 mg/L, 0.17 mg/L, 0.17 mg/L, and 0.16 mg/L, respectively. These results could be attributed to the similarity among Europium, Gadolinium, and Terbium. They are in sequence in the periodic table and therefore present very close ionic radii, restricting their separation. Considering the sum of all RE, Viewgam® was the most contaminated formulation (mean of 2.16 mg/L) and Magnevist® the least (mean of 0.64 mg/L). Although the RE are chemically similar, the other RE do not perform as Gd as a contrast agent; therefore, their presence in formulations may be a matter of concern.

Comparative analysis of soil magnetic susceptibility and concentration of rare earth elements in soil of problematic areas

Abstract Soil contamination with rare earth metals (REE) can have both direct and indirect connection with industrial activity and ore-exploration. In the studies conducted so far, the presence of rare earth elements in coal seams, coal combustion waste as well as fly ash was found. It is important that detailed studies of the REE content in soil were not carried out in Poland. Until now, in a few studies, a high content of cerium and lanthanum was found in relation to the average content of the torn ones in the world. This work focuses on the areas under the influence of the industry associated with the extraction and combustion of hard coal, but also with other types of industry. Analyzes of REE content in soil were conducted in selected areas of the Upper Silesian Industrial Region and Norway, located near the Bjornevatn mine. In study areas, soil samples were collected and used for chemical and magnetometric measurements. Firstly, concentrations of REE were determined, and after that soil samples were used to measure soil magnetic susceptibility. Finally, statistical analyses were performed in order to check the correlation between REE concentrations in soil and soil magnetic susceptibility.

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.

Quantitative x-ray spectral determination of rare-earth metals in products of metallurgy

A technique for x-ray spectral quantitative determination of lanthanides in solid products of metallurgical industries have been developed and coupling equations have been derived that make it possible to calculate the concentration of rare earth metals with an accuracy that meets the requirements of the technological process. The study performed samples of the analyte with monochromatic gamma or x-ray radiation with simultaneous recording of the intensities of the characteristic radiation and incoherently scattered radiation by the same breakdown of the primary radiation, the concentration measurement of the element being determined is carried out according to the analytical parameter taking into account the effect of the background of the characteristic radiation. The technical result was the provision of the possibility of determining the concentration of elements in samples of different chemical and material composition, having a different structure and density, without identifying the phase composition, but with a preliminary correction of the background.

Sorption rerecovery and concentration of rare-earth metals from extraction phosphoric acid. Review

The review covers the methods for sorption recovery and concentration of rare-earth metals (REM) from solutions of extraction phosphoric acid (EPA). Sorption extraction of the REM seems most appropriate at the stage of primary concentration, but a significant amount of iron (III) and calcium as the most interfering impurities are the problem, both at the stage of sorption and at the stage of desorption. The results of studies on the sorption of trivalent ions of cerium, lanthanum and iron on sulfonic cation-exchange resin KU-2-8 and macroporous weakly acidic cation exchange Cybber CRX 300, are presented. It is established that the cation exchanger Cybber CRX 300 by exchange capacity for lanthanum and cerium and kinetic properties is inferior somewhat to sulfonic cation-exchange resin KU-2-8 at sorption from acidic solutions, but can be used to concentrate and separate the REM from iron. The review presents data of the pilot trials of the technology for extracting rare-earth metals from dihydrate extraction phosphoric acid (45 % P2O5) produced by «PhosAgro-Cherepovets» JSC (RU). The results of tests of sorbents TP260, Purolite S957 (Monophos), sulfonic cation-exchange resin РРС 160 and sorbent АА03 at sorption: from sulphate solution after decomposition of phosphate raw materials; from a solution of hydrolysis sulfuric acid after precipitation of titanium dioxide; from sulfuric acid solutions after sorption of uranium are presented. The distribution of rare-earth metals during their sorption by KU-2 sulfonic cation-exchange resin from solutions of phosphoric acid, as follows: dihydrate EPA partially evaporated 43.69 wt. % P2O5, «Balakovo Mineral Fertilizers» JSC; dihydrate EPA, without evaporation 26.09 wt. % P2O5, OJSC «Ammofos»; dihydrate EPA, evaporated 52.54 wt. % P2O5, «Ammofos» OJSC, was studied. The distribution coefficients of individual lanthanides are obtained. The analysis of literature data has shown that the choice of sorbent is the most difficult task when developing the technology for sorption extraction of REM from multicomponent solutions.

EXTRACTION OF RARE-EARTH ELEMENTS BY MIXES OF ISOMERS OF TRIBUTYLPHOSPHATE WITH NITRATE TRIALKYLMETHYLAMMONIUM

Results of studying of extraction of nitrates of rare-earth elements (REE) and trialkylmetylammoniya nitrate (TAMAN) are given by mixes of isomers of tributyl phosphate (TBP). Tri-iso-butylphosphate and tri - sec-butylphosphate are investigated as isomers of normal tributylphosphate. The water phase contained 8 mol/dm3 nitrate of ammonium and 5.10-4 mol/dm3 of neodymium nitrate at рН = 2-3. The content of extractants in isomolar series was varied in the range of 0-0.3 mol/dm3. It was established that synergistic effect decreases in a series of TBP> TIBP> TvtBP. Synergistic effect is calculated as the distribution coefficient relation at extraction by mix of extractants to the sum of coefficients of distribution at extraction by each of extractants. Synergistic effect reaches its maximum value at the ratio: [NPOC] : [TAMAN] = 2 : 1 for TBP and 4-5 : 1 for TiBP, TvtBP, and the absolute value fluctuates within 10-50 at extraction of microconcentration of REE. It is noted that the method of isomolar series is applied incorrectly in many researches with the violation of the fundamental requirements (variable concentration of rare earth metals and acid in the aqueous phase, an assumption of a possibility of simultaneous existence of several solvate, variable concentration of salting-out owing to extraction into the organic phase, the association and polymerization in the organic phase, etc..), which must be followed when using this method. Мultiple saturation method (MSM) is offered for a correct application of the method of isomolar series. The method consists in the fact that the organic phase is saturated repeatedly (5-6 times) with the original aqueous solution until a constant composition of the aqueous phase at all points of isomolar series. It is possible to believe that the organic phase is responsible for the deviation from the additivity in this case. It was established that synergistic effect tends to unity or virtually disappears in the extraction of REE macroamounts method of ofisomolar series of multiple saturation. It is shown that value of synergistic effect approaches unity at gadolinium nitrate extraction by isomolar mix in the MSM mode. Synergistic effect for a mixture of rare earth elements is close to unity in the extraction of REE mixtures macroamounts of TiBP and TAMAN, and the individual elements are distributed in accordance with the extraction characteristics of each of the extractants alone: synergistic effect for several elements of cerium is greater than one, and yttrium - somewhat less than one. It is suggested that if there is free extragent the formation of mixed solvate may be explained by the steric effect, which disappears at saturation of extracgent.Forcitation:Val'kov A.V., Khmelevskaya N.D. Extraction of rare-earth elements by mixes of isomers of tributylphosphate with nitrate trialkylmethylammonium. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 7. P. 54-60

ИЗУЧЕНИЕ ФАЗОВОГО СОСТАВА И ЭЛЕКТРОПРОВОДНОСТИ СПЛАВОВ СИСТЕМЫ Cu–Cr–Si–Ce–La

The phase composition and electrical conductivity of 12 as-cast samples of the Cu–Cr–Si–Ce–La system alloys were investigated. The concentration of chromium in the samples ranged from 0.5 to 1.0 wt. %; the concentration of silicon in samples was from 0.1 to 1.3 wt. %; the concentrations of rare-earth metals (cerium and lanthanum) ranged from 0.1 to 0.5 wt. %. The samples were studied by scanning electron microscopy and micro-X-ray spectral analysis, as well as by X-ray phase analysis. It is established that in the experimental samples in equilibrium with a solid solution based on copper, depending on the concentration of the alloying elements, intermetallides Cu6Ce and Cu6La, inclusions of metallic chromium, chromium silicides Cr3Si and Cr5Si3, and also silicide of lanthanum and cerium (La,Ce)Si2 were formed. In the course of the work, the Vickers microhardness was measured on the thin sections of the samples under study. The dependence of the values of the microhardness HV on the composition of the experimental samples was established. With increasing silicon concentration for fixed values of chromium, cerium and lanthanum, the microhardness values were increased. Also in the course of this study, the electric conductivity of the experimental samples was determined by a non-contact method in a rotating magnetic field at a temperature of 20 °C. The dependence of the electrical conductivity of the samples on the concentrations of alloying elements was determined. The data obtained in the course of this work may be of interest to engineers in the analysis of the use of rare earth metal additives in bronzes.

Effect of Rare Earth Metals on the Microstructure of Al-Si Based Alloys.

The present study was performed on A356 alloy [Al-7 wt %Si 0.0.35 wt %Mg]. To that La and Ce were added individually or combined up to 1.5 wt % each. The results show that these rare earth elements affect only the alloy melting temperature with no marked change in the temperature of Al-Si eutectic precipitation. Additionally, rare earth metals have no modification effect up to 1.5 wt %. In addition, La and Ce tend to react with Sr leading to modification degradation. In order to achieve noticeable modification of eutectic Si particles, the concentration of rare earth metals should exceed 1.5 wt %, which simultaneously results in the precipitation of a fairly large volume fraction of insoluble intermetallics. The precipitation of these complex intermetallics is expected to have a negative effect on the alloy performance.

Extraction of lanthanides by polysulfone microcapsules containing EHPNA. I. Piercing method

Since the conventional liquid-liquid extraction method suffered from a series of problems such as inefficiency of one stage extraction, vast device occupation and severe emulsification, we adopted microcapsule (MC) technique to change the former liquid-liquid extraction to liquid-solid extraction. Firstly, the piercing method was performed to prepare the empty polysulfone (PSF) microcapsules, which was easy to implement and control. Secondly, the ultrasonic approach was utilized to prepare the functional microcapsules containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHPNA). We focused on a key factor of the molar ratio of PSF over 1-Methyl-2-pyrrolidinone (NMP), attaining a loading ratio as high as 7.21 g-EHPNA/g-PSF. Thirdly, we examined the kinetics and thermodynamics of extraction. Kinetic results demonstrated that equilibrium was reached within two hours, with an extraction rate of Sm3+≈Er3+>La3+; Thermodynamic results showed that the extraction of lanthanides complied with the Langmuir law, with an extraction capacity of 0.25–0.30 mmol/g-microcapsule. Fourthly, stripping experiment indicated that three hours were required to accomplish equilibrium for La3+ and Sm3+ while longer hours for Er3+. Finally, seven extraction-stripping cyclic experiments were performed for three mixed elements, the results of which revealed that Sm3+ and Er3+ maintained constantly high extraction amount whilst La3+ leveled off at approximately 50%. This proposed polysulfone microcapsule containing EHPNA is suitable to be applied to extraction and concentration of rare earth metals.

Investigating the composition of dissolved organic matter in natural water in rare earth mine using EEM-PARAFAC analysis.

In this study, we have characterized three fluorescent components of dissolved organic matter (DOM) in the surface and underground water of one rare earth element ore district by excitation-emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC). Two protein-like components (C1, tyrosine and C2, tryptophan) and one humic-like component (C3) were identified by the DOM Fluor-PARAFAC model, with C3 constituting more than 95% of the total DOM, while C1 and C2 occupying a tiny fraction of DOM. The distribution of three PARAFAC-identified components was strongly influenced by the river direction, terrain and location of various water samples. The results suggested that DOM of samples collected from downstream or a central region had higher fluorescence intensity than those of upstream or surrounding the center. In addition, a negative linear correlation (R(2) = 0.8465) between pH (5.7-9.2) and fluorescence intensity of C3 was observed, indicating that the increase of pH might enhance the intensity of fluorescent humic-like substances. Although the fluorescence intensity of C1 and C2 was independent of pH changes, strong quenching effects of different heavy metals were presented for C1, and evident positive correlations between C2 and concentrations of rare earth metals (La, Ce, Tb, Dy, Tm, etc.) were observed, which showed that tyrosine-like (C1) and tryptophan-like (C2) substances were assumingly responsible for metal binding and adsorption in water, respectively. Based on EEM-PARAFAC modeling, all the fluorescence EEMs of samples could be decomposed into a three-component model, and their potential applications in water quality monitoring and metal-binding indicator were likely to be developed in the fluorescence analysis of natural water.

Study of Cell Antigens and Intracellular DNA by Identification of Element-Containing Labels and Metallointercalators Using Inductively Coupled Plasma Mass Spectrometry

The enumeration of absolute cell numbers and cell proliferation in clinical samples is important for diagnostic and research purposes. Detection of cellular DNA with fluorescent dyes is the most commonly used approach for cell enumeration in cytometry. Inductively coupled plasma mass spectrometry (ICPMS) has been recently introduced to the field of protein and cell surface antigen identification via ICPMS-linked immunoassays using element-labeled affinity reagents such as gold and lanthanide-conjugated antibodies. In the present work, we describe novel methods for using metallointercalators that irreversibly bind DNA and low concentrations of rare earth metals added to cell growth media for rapid and sensitive measurement of cell numbers by mass spectrometry. We show that Ir- and Rh-containing metallointercalators are useful reagents for labeling cells and normalizing signals when studying antigen expression on different types and numbers of cells. Results are presented for solution analysis performed by conventional ICPMS and compared to measurements obtained on the novel flow cytometer mass spectrometer (FC-MS) instrument, designed to analyze multiple antigens and DNA simultaneously in single cells.

Overview of the effects of rare-earth elements used as additive materials in molten carbonate fuel cell systems

From the viewpoint of materials issues, there are some problems in molten carbonate fuel cell (MCFC) systems due to the corrosive and evaporative electrolytes and the high pressure caused by a stack in temperature of 650°C. The rare earth metals (RE) in as material additives primarily improve the creep resistance, corrosion resistance and high temperature resistance of materials. However, efforts to enhance the properties of MCFC materials using RE have not yielded the marked effects associated with their use in solid oxide fuel cells (SOFC). Therefore, we have conducted this review in order to describe and discuss the effects of RE as additive materials in the context of MCFC. This review also provides information regarding the development of MCFC materials using RE. The incorporation of low concentrations of RE into previously RE-free materials may improve the stability of these materials to some degree, and also effect an increase in the cell efficiency of MCFC. La2O3-added cathode materials have primarily been applied as alternative materials, for the reduction of the dissolution of conventional NiO cathodes. Ce and Dy have both been theorized to possibly enhance the stability of anode electrode materials. Ce and La can both be employed as additives which enhance the stability of reforming catalysts. The addition of La2O3 to electrolytes has been previously shown to reduce the degree of dissolution in cathodes. Ce-based ceramics are thought to be promising coating materials, and it is believed that they may help to prevent the corrosion of the separator. However, future research into materials which exhibit long-term stability and low electrical conductivity is clearly warranted, as the field is in its infancy.

Effect of sodium ions on the extraction of rare earth metals by liquid surfactant membranes containing a calix[4]arene carboxyl derivative

A novel host compound calixarene has been applied as a mobile carrier for the separation and concentration of rare earth metals by liquid surfactant membranes (LSMs). Using the novel carrier, extraction of rare earth metals (Ho, Er and Y) by LSMs was systematically studied in a stirred cell. Extraction behavior of rare earth metals by the carboxyl derivative of calix[4]arene was found to be extremely sensitive to coexisting sodium ions in the feed solution. The extractability of rare earth metals was remarkably enhanced by the addition of sodium ions. The permeation rate of rare earth metals through the LSMs in the presence of sodium ions was 100-fold higher than that without sodium ions. This enhancement of the permeation rate is attributed to the preferential conformation change in the host compound of calixarene initiated by sodium ions. The permeation mechanism of rare earth metals by LSMs is elucidated by an interfacial reaction model.

Effect of synthesized surfactants in the separation of rare earth metals by liquid surfactant membranes

Synthesized surfactants have been applied to the separation and concentration of rare earth metals by liquid surfactant membranes (LSMs). Using newly synthesized surfactants (nonionic dioleyl L-glutamate ribitol; cationic dioleyl L-glutamate quaternary ammonium chloride), extraction of lanthanum (La), praseodymium (Pr), and neodymium (Nd) by LSMs was carried out with (2-ethylhexyl)phosphonic acid mono(2-ethylhexyl) ester as a carrier. The effects of the synthesized surfactants on the extraction and separation of these metals were investigated. Rate constants in LSMs were obtained from the analysis with an interfacial reaction model for each rare earth metal. It was found that the surfactant strongly affects the extraction rate and separation of rare earth metals by LSMs. Among them, a cationic surfactant having two oleyl chains showed the best separation factor in the extraction of La, Pr, and Nd by LSMs. Further, the extraction rate of the cationic surfactant was about 40 times higher than that of a commercial surfactant such as Span 80

Equilibrium distribution of rare earth elements between molten KCl-LiCl eutectic salt and liquid cadmium

Distribution experiments for several rare earth elements (La, Ce, Pr, Nd and Y) between molten KCl-LiCl eutectic salt and liquid Cd were carried out at 450, 500 and 600°C. The material balance of rare earth elements after reaching the equilibrium and their distribution and chemical states in a Cd sample frozen after the experiment were examined. The results suggested the formation of solid intermetallic compounds at the lower concentrations of rare earth metals dissolved in liquid Cd than those solubilities measured in the binary alloy system. The distribution coefficients of rare earth elements between two phases (mole fraction in the Cd phase divided by mole fraction in the salt phase) were determined at each temperature. These distribution coefficients were explained satisfactorily by using the activity coefficients of chlorides and metals in salt and Cd. Both the activity coefficients of metal and chloride caused a much smaller distribution coefficient of Y relative to those of other elements.

Influence of rare-earth metals on the properties of austenitic chromium-nickel steel

1. Rare-earth metals have a substantial effect on the amount, size, and composition of nonmetallic inclusions in austenitic chromium-nickel steel, and also modify the composition and quantitative relationship between spinels and silicates. 2. Rare-earth metals increase the ductility of the steel in long-term tests. With increasing concentrations of rare-earth metals the time before fracture first increases sharply, reaching a maximum at 0.1%, and then decreases to the original value. The creep rate first decreases or does not change, and then increases sharply. 3. The scale resistance of austenitic chromium-nickel steels is increased considerably by the addition of rare-earth metals. 4. Rare-earth metals have no effect on the grain size of the steel or the resistance to intercrystalline corrosion.