Rare Earth Mixtures Research Articles

Simultaneous determination of neodymium and erbium in rare earth mixture with 5,7-dibromo-8-hydroxyquinoline and TX-100 by third-derivative spectrophotometry

The absorption spectra of 4f electron transitions of the complexes of neodymium and erbium with 5,7-dibromo-8-hydroxyquinoline in the presence of octylphenol poly(ethyleneglycol)ether have been studied by normal and third-derivative spectrophotometry. The proposed method is free of interference of other rare earths. The calibration graphs were linear up to 18 μg/ml of neodymium and 21 μg/ml of erbium (in the final solution). The derivative molar absorptivities are 395 l.mol–1.cm−1 for neodymium and 3421.mol−1.cm−1 for erbium. The corresponding values of Sandell's sensitivity were 0.36 and 0.49 μg.cm−1, respectively. The relative standard deviations evaluated from ten independent determinations of 2.5 μg/ml of neodymium and erbium are 1.5 and 3.8% for neodymium and 1.8 and 4.1% for erbium in absence and presence of 70 μg of lanthanum, respectively. The detection limits (signal to noise ratio=2) are 0.23 μg/ml for neodymium and 0.30 μg/ml for erbium. The method has been used for the determination of neodymium and erbium in mixed rare earths with satisfactory results.

Selective determination of yttrium in geological materials by ion-interaction chromatography

Selective separation and determination of yttrium in rare earth ores have been achieved by high performance ion-interaction chromatography. Ores are decomposed by sulfuric acid and the rare earths are precipitated in a group as oxalates. Yttrium is then separated from the other rare earths on a C-18 bonded phase silica column modified with 1-octanesulfonate by linear concentration gradient elution for 20 min with 0.15 to 0.40M glycolic acid(pH 3.5). Yttrium elutes at about 10 min between samarium and neodymium, being separated selectively from all the rare earths as well as scandium, thorium and uranium. Post-column reaction detection and quantitation with Arsenazo III [2,7-bis(2-arsonophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid] are carried out at 650 nm. Quantitative results are quoted for yttrium in sophisticated, synthetic rare earth mixtures, monazite and xenotime.

An expert system for solvent extraction of rare earths

An expert system for solvent extraction of rare earths has been developed using LISP. The goal of this project was to mimic the chemists' inferential abilities to assist in the process of solvent extraction of rare earths. The system includes frequently used extractants, separation of specific rare earths, recommendation of procedures for the separation of mixtures of rare earths using (2-ethylhexyl)phosphonic acid 2-ethylhexyl monoester, selection of parameters for counter-current extraction and methods for evaluation of the technique, and the economics of the processing. The expert system runs on an IBM-PC/XT.

Solution thermochemical assay of lanthanides

A method is proposed for the determination of binary mixtures of lanthanides in nitric acid using a non-aqueous thermometric system. If the atomic numbers of the lanthanides differ by 7 or more then the precision and reproducibility of the method are analytically acceptable.

Absorption spectra of 4 f electron transitions of neodymium and erbium complexes with ferron and diethylamine. Determination of neodymium and erbium in rare earth mixtures by third-derivative spectrophotometry

The absorption spectra of 4 f electron transitions of complexes of ferron (5-sulpho-7-iodoquinolin-8-ol) with neodymium and erbium in the presence of diethylamine were measured. Their molar absorptivity at the maximum absorption bands was about 7.5 (at 574.2 nm) times greater for neodymium and 10.8 (at 519.8 nm) times greater for erbium than those in the absence of the complexing agents. Use of third-derivative spectra bond eliminates the interference of other lanthanides and increases the sensitivities for neodymium and erbium. Beer's law was obeyed from 0 to 13 μg ml −1. The relative standard deviations for the determination of 7.2 μg ml −1 of neodymium and 8.3 μg ml −1 of erbium ( n = 7) are 1.3% and 1.5%, respectively. The detection limits (signal-to-noise ratio = 2) are 0.3 μg ml −1 for neodymium and 0.4 μg ml −1 for erbium. A method for the direct determination of neodymium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.

Absorption Spectra of 4f Electron Transitions of Neodymium and Erbium with 8-Hydroxyquinoline-5-sulphonic Acid and Diethylamine Systems and Its Analytical Application

Abstract In this paper the absorption spectra of 4f electron transitions of the systems of neodymium and erbium with 8-hydroxyquino-line-5-sulphonic acid and diethylamine have been studied by normal and third-derivative spectrophotometry. Their molar absorptivities are 80 l.mol−1.cm−1 for neodymium and 65 l.mol−1.cm−1 for erbium. Use of the third-derivative spectra, eliminates the interference by other rare earths and increases the sensitivity for Nd and Er. The derivative molar absorptivities are 390 1.mol−1.cm−1 for Nd and 367 1.mol−1.cm−1 for Er. The calibration graphs were linear up to 11.8 μg/ml of Nd and 12.3 μg/ml of Er, respectively. The relative standard deviations evaluated from eleven independent determinations of 7.2 μg/ml (for Nd) and 8.3 μg/ml (for Er) are 1.3% and 1.4%, respectively. The detection limits (signal to noise ratio = 2) are 0.2 μg/ml for Nd and 0.3 μg/ml for Er. The method has been developed for determining those two elements in mixture of lanthanides by means of the third-deriv...

Study of the absorption spectra of 4f electron transitions of the neodymium complex with 8-hydroxyquinoline and octylphenol poly(ethylene glycol)ether and its analytical application

The absorption spectra of 4f electron transitions of the neodymium complex with 8-hydroxyquinoline and octylphenol poly(ethylene glycol)ether have been studied by conventional and third-derivative spectrophotometry. The absorption spectrum for neodymium at 575 nm is resolved into three bands centring at 572, 580 and 584 nm, respectively. The use of third-derivative spectra both eliminates the interference from other rare earth elements and enhances the sensitivity for neodymium. Beer's law is obeyed for 0–14 µg cm–3 of neodymium. The corresponding value of Sandell's sensitivity is 0.29 µg cm–2. The relative standard deviations evaluated from 11 independent determinations of 2.0 µg of neodymium are 0.87% for neodymium alone and 1.6% in the presence of 80 µg of lanthanum. The detection limit (signal-to-noise ratio = 2) is 0.12 µg cm–3 of neodymium. A method for the direct determination of neodymium in mixtures of rare earth elements with good accuracy and selectivity, is described.

Die chemische Zersetzung von Seltenerd-Nitraten: Eine neue Methode zur Anreicherung schwerer Yttererdnitrate im kg-Ma�stab

On addition of oxidizable organic substances to molten rare earth nitrates reaction takes place with evolution of nitric oxides and formation of basic nitrates, the two-step hydrolysis of which results in effective enrichment of heavy yttrium earths (YE) from rare earth mixtures in kg-quantities. Using methanol as reducing agent the reaction takes place at 160°C, much lower than using the method of purely thermal decomposition. In both methods after the first hydrolysis step a productYE(OH)1.5(NO3)1.5·H2O can be isolated.

Determination of neodymium in rare earth mixtures by fourth-derivative spectrophotometry

The absorption spectra corresponding to the 4f electron transitions of the neodymium complex with xylenol orange and cetylpyridinium chloride in the presence of Triton X-100 are reported. The absorption by neodymium is increased by a factor of 666, compared with that of its chloride. Fourth-derivative spectra are used to increase the sensitivity and to eliminate interferences from other rare earth elements. Beer's law is obeyed for 1.4–7.2 μg Nd in 25 ml of solution. The relative standard deviation is 0.8% for 5.0 μg/25 ml ( n = 7). Detection limits are 5.0 ng ml −1 for Nd alone and 11.0 ng ml −1 in the presence of 45 ng of lanthanum. Satisfactory results were obtained for the determination of neodymium in rare earth mixtures.

The rare earths: their minerals, production and technical use

Deposits of rare earth minerals are of magmatic, sedimentary and of metamorphic type. The most important economic mineralizations are the magmatic to hydrothermal bastnaesite deposits of Mountain Pass (USA) and of Bayan Obo (China P. R.), as well as the monazite-bearing coastal placers of Australia, Brazil and India. No shortage in rare earth supply will be faced by the world economy in the next years. China has by far the most important reserves. An increased demand can be observed for individual rare earths of high purity, and for mixtures of specific rare earths

Development of a Photochemical Route for Upgrading Europium from Aqueous Lanthanide Mixtures

Detailed scodtee have been carried out on the parametric dependence of the photochemical reduction of europium (III). The paper presents the salient features of an efficient process developed for tbe pbotnchemical reduction of europium (Ill} ions in aqueous solutions and its application in the seperation of europium from synthetic lanthanide mixtures as well as from a 70% europium concentrate obtained from the indigenous monazite sources. Further work is however needed to establish the commercial potential of the process.

Simulation of atomic spectra—II. Mutual spectral interferences of rare earth elements in the inductively coupled plasma

This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta B (SAB). The hardcopy text, comprising the main article and an appendix, is accompanied by a diskette with a program, data files, and a manual. The text details the purpose of the work, with emphasis on the spectroscopic aspects, and the appendix provides the essential information for accessing the diskette and using program and data. Additional tutorial guidance is provided by the manual. The program primarily concerns the simulation of the spectra of rare earth elements (REE) as interferents in 80-pm wide spectral windows centred about the wavelengths of 26 prominent lines of Ce, La, Nd, Pr, and Sm. The program essentially covers the model described in Spectrochim. Acta 43B, 1365 (1988) and the database is identical to the experimental database published in Spectrochim. Acta 44B, 31 (1989). Accordingly, the data are for an inductively coupled plasma (ICP). The program enables the user to simulate spectra with the spectral bandwidth as an optional variable. The user may then generate spectra of both single REEs, without or with analyte, and mixtures of REEs of any composition, also without or with analyte, whereby for spectra with analyte the display includes the blank spectrum. Displays are accompanied by legends providing a set of essential numerical data. In addition, particular program options allow the generation of numerical data only, one of them being the calculation of true detection limits. This option permits it to perform, within the limited scope of the database, line selection for complex REE samples in a rational way. The program operates, in principle, with the default values of the ICP Doppler temperature (6800 K) and “average” ICP a-parameter of the Voigt profile (0.5), but these values may be optionally modified. Similarly, the user may add new data files to the base and thus also apply the program for other purposes and outside the REE environment, such as model studies in general, and for learning or teaching, as explained in the manual on the diskette. The tutorial part of this manual provides the user not only with elementary instructions for using the program as a practical tool, but also incorporates a variety of instructive examples, including a brief “course” on spectral line profiles and spectral interferences.

Synthesis and thermal decomposition of CH3NH3Ln(SO4)2.4H2O (Ln=Tm, Yb OR Lu)

The double sulfates of Tm, Yb and Lu with monomethylammonium were obtained by evaporation of an aqueous mixture of rare earths(III) sulfate and monomethylammonium sulfate at room temperature and treatment of the concentrated mixture with ethanol. After identification of the double sulfates, they were examined by means of TG, DTG and DTA analysis, from 20 to 700°. Two clearly separated stages of thermal decomposition were evident. It was possible to determine the stoichiometry of the obtained compounds from the TG curves.

Effects of paramagnetic lanthanides on the study of carbonaceous deposits on zeolite catalysts by carbon-13 solid-state nuclear magnetic resonanace spectroscopy

Relaxation and spin-counting measurements have been used to probe the extent to which {sup 13}C NMR spectroscopy with cross polarization and magic-angle spinning is a useful technique for characterizing carbonaceous (coke) deposits in zeolite catalysts containing rare-earth cations. Such ions were anticipated to complicate this analysis as a result of paramagnetic shifts and/or relaxation effects. Contrary to expectations, no paramagnetic shifts were observed for carbonaceous deposits in the rare-earth-exchanged Y-type zeolites examined. Even more surprising was that the mixture of rare earths used in industrial catalysts has negligible effects upon the relaxation processes central to cross polarization. Small concentrations of lanthanides with long electron spin-lattice relaxation times (in particular gadolinium), however, have a deleterious effect on characterizing carbonaceous deposits by decreasing the proton rotating-frame spin-lattice relaxation time.

Spectrophotometric study and analytical applications of lanthanide-kojic acid complexes: Direct determination of Nd, Ho and Er in mixtures of rare earths

The complexes of the rare-earth metals with kojic acid in weakly alkaline solution are reported. The characteristic absorbances of neodymium, holmium and erbium can be increased by factors of 4.3, 11.0 and 6.4 respectively, compared with those of the chlorides. The third-derivative spectra have been used to eliminate the interference of Ce, La and Y, and the sensitivities are again increased, by a factor of 6–9.

T*-phase superconductivity

The T⋆-phase is a mixed rare earth oxide phase forming at the composition R2CuO4. Its crystal structure is intermediate between the La2CuO4 and Nd2CuO4 structures. Sr-doped samples have Tc onsets as high as 37 K. We discuss the systematics of Tc of T⋆-phases as a function of Sr doping, rare earth mixture and oxygenation. Structural and transport data will also be presented.

Second-derivative spectrophotometric determination of scandium in rare earth mixtures with chlorophosphonazo- p-Cl(CPApC)

A method based on the Sc-CPAcC β-type complex for the second-derivative spectrophotometric determination of scandium has been developed. The determination range is 0–5 μg of scandium in 25 ml of solution and the detection limit was found to be 4.1 ng ml −1. Most of the rare earths in reasonable amounts do not interfere with the determination. The method has been used to determine scandium in rare earth mixtures.

γ-Induced reduction of Eu(III) in aqueous solution

γ-radiation of Co60 has been applied to reduce Eu(III) to Eu(II) in aqueous solutions of the mixture of rare earths. The kinetics of the process has been investigated as a function of the absorbed radiation dose and organic additive concentration.

Application of the co-luminescence effect of rare earths: simultaneous determination of trace amounts of samarium and europium in solution

The enhanced luminescence of samarium and europium in a thenoyltrifluoroacetone-1,10-phenanthroline-Triton X-100 system in the presence of Gd3+ has been studied. It was shown that the sensitivities were increased by 1–2 orders of magnitude compared with those in the system containing no Gd3+. Under optimum conditions the detection limits were 5.0 × 10–10M for samarium and 7.5 × 10–12M for europium. The procedure was applied satisfactorily to the simultaneous determination of samarium and europium in mixtures of lanthanides.

Relative intensity database of L-Shell lines of lanthanides and analysis of the PIXE spectra

The PIXE spectra resulting from proton beam bombardment in the energy range of 1 to 2.5 MeV of the thin targets of 14 lanthanides were measured using a Ge detector to obtain a relative intensity database of the L-shell lines. The database utilizes the relativistic Hartree-Slater (RHS) emission rates reported by Scofield. To correct the other quantities affecting the relative intensities such as L-subshell ionization cross sections etc., empirical factors are introduced and the values are determined by the least squares method. The reduced chi-squared value is 0.85 ± 0.4 for 90 spectra. The relative intensities of Nd, Dy and Yb obtained at 2 MeV are compared with the recent ECPSSR approach by Cohen and Harrigan, and it is found that these results are in fairly good agreement. The PIXE spectra of the mixtures of lanthanides and the crude rare-earth chlorides from monazite are analyzed by use of the database. The reasonable analytical results obtained confirm the practical utility of this approach. The performance of a program, PIXS, developed for doing the analysis on a personal computer is also reported.