Energy-adjusted pseudopotentials for the rare earth elements

Nonrelativistic and quasirelativistic energy-adjusted pseudopotentials and optimized (7s6p5d)/[5s4p3d]-GTO valence basis sets for use in molecular calculations for fixed f-subconfigurations of the rare earth elements, La through Lu, have been generated. Atomic excitation and ionization energies from numerical HF, as well as SCF pseudopotential calculations using the derived basis sets, differ by less than 0.1 eV from numerical HF all-electron results. Corresponding values obtained from CI(SD), CEPA-1, as well as density functional calculations using the quasirelativistic pseudopotentials, are in reasonable agreement with experimental data.     

稀土萃取分离技术方法研究

稀土在工业诸多领域中发挥着关键作用,在增材制造材料和介电材料等高新技术领域均显示出可期的应用前景。稀土元素的分离是衔接稀土资源与高性能稀土功能材料的关键过程,所以高效提纯稀土元素变得尤为重要。本文梳理了化学沉淀法、离子交换与吸附法、萃取色层法、溶剂萃取法、液膜分离法这些经典方法和化学气相传输法、氧化还原法、萃取沉淀法、微生物法、非平衡溶剂萃取法这些新技术方法的优缺点和适用性,侧重分析了这些技术方法在节能减排方面的最新研究情况,并展望了稀土分离提纯领域的重点发展方向,以期为稀土资源的绿色高效开发利用提供依据和借鉴。     

ICP-MS同时测定植物性食品中稀土元素的方法研究

建立了植物性食品中16种稀土杂质(Sc、Y、La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb和Lu)元素的电感耦合等离子体质谱(ICP-MS)的分析方法.考察了基体效应及质谱干扰,应用In内标,有效地补偿基体效应所引起的测量偏差,建立修正公式校正质谱干扰.对照分析了参考标准物质.对所测定元素,校正曲线的相关系数为＞0.9990,方法的检出限低于2.2 pg/g(Sc为95pg/g),回收率为92%～106%,RSD优于3.2%(n=7).     

Reversed-phase thin-layer chromatography of the rare earth elements

Summary Partition chromatographic behaviour of the rare earth elements on C₁₈ bonded silica reversed-phase material has been investigated by thin-layer chromatography in methanol — lactate media. The rare earth lactato complexes are distributed and fractionated on bonded silica layers without ion-interaction reagents. The concentration and pH of lactate solution, methanol concentration and temperature have effects on the migration and resolution of the rare earth elements. The partition system is particularly suited to separate adjacent rare earths of middle atomic weight groups, allowing the separation of gadolinium, terbium, dysprosium, holmium, erbium and thulium to be achieved by development to 18 cm distance.     

Effect of four bentonite samples on the rare earth element concentrations of selected Hungarian wine samples

Rare earth elements (REEs) were detected and determined (except Eu, and in some cases Gd, Tb and Tm) in three Hungarian wine samples - Királyleányka, Blauer Portugieser and Merlot (2004 vintage) - from the Eger viticulture area by double focusing inductively coupled plasma sector field mass spectrometry (ICP-SF-MS) in low resolution mode (R = 300). The REE average concentrations of the samples determined after microwave-assisted digestion were in the pg cm^− 3 concentration range. According to the results, among these grapes grown on volcanic slopes, the REEs uptake by the Királyleányka and Blauer Portugieser seemed to be more inhibited. Four, commercially available bentonite samples - fibrous (Gelbenton), protein containing (Evergel), and two Na bentonites (BW200 and Tükrös) - were used for wine clarifying. Gelbenton altered the less the REE concentrations of the wine samples. The lowest increase (1.1-1.5 times) was established for the Merlot red wine sample.     

茶叶中稀土元素的萃取分离-ICP-AES法测定

采用1-苯基-3-甲基-4-苯甲酰基-5-吡唑酮(PMBP)苯溶液萃取分离-ICP-AES法同时测定茶叶中15种稀土元素,消除了基体的干扰,并对样品前处理方法、萃取分离条件进行了考查.方法回收率为: 92.3%～112%,相对标准偏差＜2.5%.在最佳工作条件下,测定了茶叶标准物质(GBW07605)中稀土元素,结果与标准值吻合.     

氟化络合-ICP-MS法测定稀土金属中的难熔金属杂质元素Ta、Mo、W、Ti、Nb

针对稀土金属中难熔金属杂质元素Ta、Mo、W、Ti、Nb在HCl或HNO3中不易溶解的性质,本文在前人工作基础上,采用HF络合-ICP-MS结合的方法,有效地将上述元素溶解在溶液中,并利用ICP-MS高灵敏度和多元素同时测定的优势,成功建立了稀土金属中难熔金属杂质元素Ta、Mo、W、Ti、Nb的测定方法。其操作过程较传统化学方法简便,灵敏度也更高。本文分析了氢氟酸的络合过程,试验了稀土氟化物沉淀对被测元素的吸附作用和内标法的校正作用。方法检出限在0.3～1.5ng／mL,测定下限0.0005％～0.0010％,回收率在89.2％～118.9％,相对标准偏差为4.6％～9.7％。     

Optimization of preparative chromatographic separation of multiple rare earth elements

This work presents a method to optimize multi-product chromatographic systems with multiple objective functions. The system studied is a neodymium, samarium, europium, gadolinium mixture separated in an ion exchange chromatography step. A homogeneous Langmuir Mobile Phase Modified model is calibrated to fit the experiments, and then used to perform the optimization task. For the optimization a multi-objective Differential Evolution algorithm was used, with weighting based on relative value of the components to find optimal operation points along the Pareto front. The objectives of the Pareto front are weighted productivity and weighted yield with purity as an equality constraint. A prioritizing scheme based on relative values is applied for determining the pooling order. A simple rule of thumb for pooling strategy selection is presented. The multi-objective optimization gives a Pareto front which shows the rule of thumb, as a gap in one of the objective functions.     

Synthesis of rare earth monoxides

The standard Gibbs energy changes for the formation of an ionic or metallic monoxide from rare earth metal and sesquioxide have been calculated. Under high pressures ionic ytterbium monoxide and lighter rare earth metallic monoxides should be obtained, which is confirmed by experiments in a belt-type apparatus in the range 15–80 kbar and 500-1200°C. For Ln =La, Ce, Pr, Nd, Sm, a face-centered cubic compound is obtained from each reaction. The cell parameters are respectively 5.144, 5.089, 5.031, 4.994, and 4.943 ± 0.005A?. The compounds appear golden yellow with a metallic luster. From chemical analyses and cell parameter consideration it is concluded that these compounds are the rare earth monoxides. For Ln =Gd, Dy, Tm, no reaction is observed at 50 kbar and 1000°C. The rare earth monoxides show a variety of properties: LaO, CeO, PrO, and NdO are metallic with the rare earth in the trivalent state; EuO and YbO are semiconductors with the rare earth in the divalent state; SmO is metallic with samarium in an intermediate valence state close to 3.     

Selective preconcentration of rare earth elements by substoichiometric precipitation of calcium oxalate and its application to the neutron activation analysis of biological material

A preconcentration method for trace amounts of rare earth elements (REs) based on the substoichiometric precipitation of calcium oxalate was developed. RE(III) was quantitatively coprecipitated with calcium oxalate which had been precipitated from the calcium of a macrocomponent in a biological sample by addition of a substoichiometric amount of oxalate. In this way high selectivity for RE(III) from other elements was achieved. The method was applied to the neutron activation analysis of a biological sample (NBS SRM 1572 Citrus Leaves), and Sc, La, Ce, Pf, Nd, Sm, Eu, Th, Dy, Ho, Yb and Lu were determined with a relative standard deviation of less than 5%.     

Influence of different bentonites on the rare earth element concentrations of clarified Romanian wines

The rare earth element (REE) concentrations of 19 Romanian young wine samples originating from the Dealurile Moldovei viticulture area were determined by double focusing inductively coupled plasma mass spectrometry (DF-ICP-MS) after microwave-assisted digestion with nitric acid. The determination of Eu was hampered by the BaO molecular interference. Generally, the red wine samples were more concentrated for REEs than the white wine samples studied. The REE concentrations of the four bentonites (Gelbenton, Evergel, BW200, Tükrös) determined after their fusion were higher by three orders of magnitude than those of the wine samples. After a simulated wine purification process performed with these bentonite samples and a red and white pool samples, the REE concentrations of the clarified wine samples increased by 1.2–1.5 times for red, and 1.3–3 times for white wines in case of the fibrous bentonite sample (Gelbenton), by about 2–5 times in case of the bentonite containing ovalbumin, caseine and gelatine (Evergel), meanwhile this factor was about 20–25 for Na bentonite powder samples (BW200, Tükrös). On basis of the chemometric evaluation using the REE concentrations as input data, the majority of the Feteasca wines belonged to the same cluster as well as the two Cabernet Sauvignon to another subcluster. The adequate choice of the bentonite may allow the use of REEs as fingerprints for determining the wine provenance.     

Efficient recovery of rare earth elements from coal based resources: a bioleaching approach

Rare earth element (REE) resources in coal-related materials are vast. Assuming a coal production rate of 600 million short tons per year with an average REE content of 200 ppm, the potential REE resource is 120,000 tons per year, which is similar to the annual global production of REEs. Most of those resources that are associated with coal-related materials are found in association with the gangue or ash-based content from the coal ore. Under normal coal plant operation, the REEs often end up in refuse piles or tailings impoundments. In many cases, these REEs can be recovered at low cost using appropriate coal preparation, heap leaching, solvent extraction and/or selective precipitation, followed by subsequent separation and purification of individual REEs. In the present research, the processing approach uses a natural pyrite stream, which was removed during coal cleaning and used to enhance leaching. Bio-oxidation has been used commercially to accelerate leaching, and this approach has been applied to coal-based materials. The ferric ions generated from bio-oxidation oxidize sulfide minerals such as pyrite, which generates acid. Both acid and ferric ions are helpful for leaching REEs, as well as for removing residual sulfides, thereby preventing future acid mine drainage and related liabilities. It can be seen that, recovery of REEs from coal waste materials can enable coal producers to use untapped REEs resources to produce revenue and extend resource life while simultaneously reducing future environmental issues and costs.     

Determination of stability constants for rare earth elements and fulvic acids extracted from different soils

Fulvic acids (FAs) were extracted by alkali extraction from different soil samples in China, then purified using resins and characterized by Fourier transform infrared spectroscopy. The complexing ability of FAs was investigated by measuring the stability constants of rare earth elements (REEs) (La³⁺, Ce³⁺, Sm³⁺, Gd³⁺, Y³⁺) with FAs by the ion exchange technique. The results indicated that maximum binding ability forY³⁺ (4.414.44) was higher than other REEs (La³⁺, Ce³⁺, Sm³⁺, Gd³⁺) (0.721.03). There were two types of binding sites in the functional groups of fulvic acids. The complexing reaction followed two steps. The stability constants (K₁ and K₂) of REEs with FAs were calculated from experimental data by division of Scatchard plots into two straight-line segments. Y³⁺ (log K₁=5.72±0.05, log K₂=4.83±0.01) also has higher stability constants than the other four REEs (log K₁=4.37±0.16, log K₂=3.62±0.28).     

Determination of rare earth elements in USGS rock standards by isotope dilution mass spectrometry and comparison with neutron activation and inductively coupled plasma atomic emission spectrometry

Rare earth element (REE) concentrations in United States Geological Survey (USGS) rock standards AGV-1, GSP-1, G-2 and PCC-1 were determined by isotope dilution mass spectrometry (IDMS), neutron activation and inductively coupled argon plasma atomic emission spectrometric techniques. The procedure involved acid digestion of samples in PTFE pressure bombs and group separation of REEs by an ion-exchange method. For IDMS an additional separation step using α-hydroxyisobutyric acid as an eluent was used in a cation-exchange column to split the REEs into subgroups. Comparison of the results with literature values showed that the IDMS values are the most precise and accurate. However, the precisions and the accuracies of the other techniques are acceptable.     

Distribution of rare earth elements among chloroplast components of hyperaccumulator<Emphasis Type="Italic"> Dicranopteris dichotoma</Emphasis>

A rare earth element (REE) hyperaccumulator, Dicranopteris dichotoma, that accumulates more than 0.1% REEs dry leaf mass has been discovered in southern China. The different components of chloroplast were isolated and the concentration of REEs in each component was determined by ICP-MS. The experimental data indicated that about 8% of total leaf REEs was present in the chloroplast of Dicranopteris dichotoma. In order to thoroughly study the distribution of REEs among different components of chloroplast, the membrane of chloroplast, the intact thylakoid and the photosystem II (PS II system) of D. dichotoma were isolated from the chloroplast. It was found that half of total chloroplast REEs was stored at the membrane of the chloroplast and another half was in the thylakoid. And 25% of total chloroplast REEs was bound with PS II system of D.dichotoma. The concentration of REEs in chlorophyll a was only at the level of g/g on the bases of chlorophylls. These data are useful for understanding of both the storage of REEs in chloroplast and the effect of REEs on the photosynthesis of plants.     

Preconcentration of rare earth quinolin-8-ol complexes onto activated carbon and determination by first-order derivative x-ray fluorescence spectrometry

A method is described for the determination of traces of rare earths using energy-dispersive x-ray fluorescence spectrometry (EDXRF) after preconcentration of their quinolin-8-ol complexes on activated carbon. Various parameters that influence the adsorptive preconcentration of rare earths on activated carbon, viz., pH, amounts of activated carbon and quinolin-8-ol, time of stirring and aqueous phase volume, were systematically studied. A numerical method based on a simple least-squares procedure using a fifth-order polynomial with 25 consecutive values was developed for smoothing and differentiation of EDXRF data which were previously digitized and averaged. First-order derivative EDXRF in conjunction with adsorptive preconcentration of activated carbon enables down to 10 ng ml^?1 of each rare earth element to be determined.     

Determination of rare earth, major and trace elements in authigenic fraction of Andaman Sea (Northeastern Indian Ocean) sediments by Inductively Coupled Plasma-Mass Spectrometry

Downcore variation of rare earth elements (REEs) in the authigenic Fe-Mn oxides of a sediment core (covering a record of last ∼ 40 kyr) from the Andaman Sea, a part of the Indian Ocean shows distinctive positive Ce and Eu anomalies. These positive Ce anomalies (Ce* = 1.1 ∼ 1.8) are ascribed to be due to oxidation of deep sea sediments. The large positive Eu anomalies (i.e., Eu* >1.8 to 3.2) occur within a time span near the glacial/interglacial transition (∼ 7000-14,000 yr BP) which could be due to the past hydrothermal activity or to the effects arising from sea level changes. During glacial times, the Andaman Sea was almost completely isolated due to low sea level, leading to a reduction in sediment supply from the Ayeyarwady River. The variations of metal abundances (i.e., Ca, Al, Mn, and Fe) in the authigenic fraction provided independent information to evaluate the water column physicochemical changes during the glacial/interglacial transition period. The studied sediment core records changes in riverine inputs and reflects depositional changes related to sea level fluctuations and climatic events over the past 40 kyr in the Andaman Sea.     

The role of rare earth elements and Mn(2+) point defects on the luminescence of bavenite

Natural fibrous crystals of bavenite (Ca₄Be₂Al₂Si₉O₂₆(OH)₂) collected in intra-granitic pegmatite bodies of Bustarviejo (Madrid, Spain) have been examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron microprobe (EMPA) and inductively coupled plasma-mass spectrometry (ICP-MS). The strong luminescence emissions of bavenite using thermoluminescence (TL), cathodoluminescence (CL) and its thermal stability have been recorded, looking for new physical properties and new phosphor or dosimetric uses. The bavenite luminescence takes place in the 5d electron shell that interacts strongly with the crystal field; the spectra bands assignment are Gd³⁺ (319 nm), Sm³⁺ (562 and 594 nm), Dy³⁺ (572 nm) and Tb³⁺ (495 nm). A Mn²⁺ band at about 578 nm in Ca²⁺ sites is present as a broad band that overlaps with the Dy³⁺, Sm³⁺ and Tb³⁺ bands. Mn²⁺ is a transition metal ion that has an electron configuration of 3d⁵ and interacts strongly with the crystal field (d → d) transition. Stability tests at different temperatures show clearly that the TL glow curves at 400 nm in both irradiated and non-irradiated bavenite samples track the typical pattern of a system produced by a continuous trap distribution. The ICP-MS analyses show concentrations of Yb = 29.7 ppm, Dy = 22.7 ppm, Sm = 9.45 ppm, Nd = 8.95 ppm and Gd = 8.15 ppm in the bavenite lattice.     

辉光放电质谱法测定稀土矿中的15种稀土元素

利用高纯铜粉与稀土矿石粉末均匀混合压片制样.混合15种高纯稀土氧化物制样建立标准工作曲线,校正15种稀土元素相对灵敏度因子,再进行定量分析.结果 表明,稀土元素工作曲线的线性方程相关系数R2均大于0.996,相对标准偏差(RSD)小于5％,满足定量分析要求.测定结果与电感耦合等离子体质谱法(ICP-MS)和电感耦合等离...     

A study on the dispersion, preparation, characterization and photo-degradation of polypropylene traced with rare earth oxides

This research work deals with the effect of rare earth oxides on the PP matrix with respect to the thermal and mechanical properties and to the photo-degradation under UV irradiation exposure. The rare earth oxides are used as tracers for the identification of polymer materials, in order to have an economically efficient recycling and high speed automatic sorting of plastic wastes. The addition of 0.1 wt% of such particles of a micrometric size has a minor effect on the mechanical and thermal properties of the traced materials, as well as on the photo-degradation of the polymer after UV irradiation exposure. For 1 wt% tracer content, before UV irradiation treatment, the melting and crystallization temperatures as well as the thermal stability of the PP matrix are slightly increased, whereas the elongation at break decreases from 10 to 50% for a cross-head speed of 250 mm/min. However, the addition of 1 wt% of CeO₂ improves the photo-degradation resistance of the PP matrix to UV exposure due to the UV light screening effects offered by these particles. The SEM images together with the results obtained from image processing show a homogenous dispersion of tracers in the PP matrix.