Sorption in the chemistry of rare earth elements

Sorption methods for the concentration and separation of rare earth elements are reviewed. Sorbents based on organic polymers, specifically strongly and weakly acidic cation exchangers, anion exchangers, and complexing sorbents, are successively considered. Data on the use of inorganic sorbents and solid phase extractants in the rare earth chemistry are also given. Considerable attention is paid to hybrid organomineral materials constituting a promising class of sorbents. Advantages and disadvantages of using biosorbents, molecularly imprinted sorbents, and nanosorbents for the concentration and separation of rare earths are discussed.     

Activation of leaching of rare earth elements from phosphohemihydrate

Treatment of fresh phosphohemihydrate obtained in processing the Khibiny apatite concentrate by hemihydrate sulfuric acid method was suggested by solutions containing alkali metal fluorides. It was shown that such treatment reduces the transit time of low-hydrated rare earth elements phosphates contained therein, which are poorly soluble in mineral acids, into the acid form from 2 months to 4–8 h.     

Determination of rare earth elements impurities in high purity uranium

A sensitive radiochemical procedure has been developed for the separation and determination of Dy, Sm, Gd, Eu, La and Lu in high purity uranium. The method is based on quantitative extraction of uranium using NPy/benzene as an extractant from 7M HCl solution. Rare earth elements (REE) remaining in the aqueous phase were subsequently determined by INAA.     

Separation of rare earth elements from uranium by solvent extraction and ion exchange

The detection limit of⁹⁹Tc in (,) radio-activation analysis was determined in the presence of molybdenum and compared with that of⁹⁹Tc in pure materials in the previous paper. The isotopic ratio of molybdenum in a⁹⁹Mo–^99mTc generator column could be simultaneously determined by photon activation analysis.     

O-TOF-ICP-MS analysis of rare earth elements,noble elements,uranium and thorium in river-relating species

The determination of rare earth elements (REEs), Au, Pt, Ir, Pd, Th and U in various river species was performed by the orthogonal time-of-flight inductively coupled plasma mass spectrometry (o-TOF-ICP-MS). The method working conditions were optimised in order to minimise the presence and possible spectral interferences of oxides. Ratios MO⁺/M⁺ as well as interference of light REE and Ba oxides/hydroxides with high REEs were evaluated and confirmed to be insignificant. Using the internal standard Re, non-spectral matrix effects (originally decreasing of intensities up to 15%) were overcome and recoveries were found from 92 to 105% for all matrices analysed. For solutions, limits of detection (3σ) were 0.14–0.82 for REEs, Th, U and Y, 1.18 for La, 4.3–5.6 for Au, Pt, Ir and Pd 11 for Sc (all in ng L^?1). The Principal component analysis was used for classification of samples according to their places of origin successfully. The o-TOF-ICP-MS was proved to be a very sensitive and suitable technique for bio-monitoring purposes and was employed in the analysis of biota samples (fish, insect, profiles, benthal growths) originated from five different places in the river Elbe (Czech Republic).     

Reaction between rare earth elements and HFNO2 solution

Rare earth elements react with HFNO₂ solution to produce nitrosylium fluorometallates (NO)_xLnF_x+3. The value of x is 1.0 or 1.5 for light rare earth elements and 0.5 or 1.0 for heavy rare earths. Nitrosylium fluorometallates of rare earth elements can be decomposed into the simple fluoride and nitrosyl fluoride at low temperatures (46–68°C).     

Sorption of uranium complexes from aqueous solution

Summary The sorption of uranium-Arsenazo III complex was studied using Dowex-1x8 and carbonized apricot stone. The results show a similarity between the two sorbents since the percentage uptake of a uranium complex in the ratio 1 : 1 reaches 100% and 92% on the Dowex-1x8 and the carbonized apricot stone, respectively. Also the uptake of the complex on either sorbents increases with increasing the hydrogen ion concentration to reach a maximum value at pH 2.5. The two sorbents are used to study the sorption of uranium(VI) from seawater in the presence of 0.002% of Arsenazo III and 10^-3M EDTA, where it is found that uranium is completely sorbed by the two sorbents.     

Polyphenylcyclopentadienyl complexes of rare earth elements

Reaction of LnCl₃(thf) _x (Ln = Y, La, Yb, Lu) with NaCp^Phn (Cp^Phn = 1,3-Ph₂C₅H₃, 1,2,4-Ph₃C₅H₂, Ph₄C₅H) leads to formation of monocyclopentadienyl dichloride complexes Yb(Ph₂C₅H₃)Cl₂(thf)₃ (1), Ln(Ph₃C₅H₂)Cl₂(thf)₃ (Ln = Y (2), Lu (3)), La(Ph₄C₅H)Cl₂(thf)₃ (4). Molecular structures of 1, 2 and the polynuclear complex [(Ph₃C₅H₂)₃Lu₄(Cl)₇(O)(thf)₃] (5), which is a partial hydrolysis product of 3, have been established by the X-ray method.     

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...     

Determination of rare earth elements at trace levels in uranium process stream samples by ion-interaction chromatography

To accurately determine ²⁴¹Am by mass spectrometry, interfering elements (IEs) including Bi, Hf, Hg, Pb, Pt, Pu and Tl need to be decontaminated. In this study, the extraction behaviors of IEs in HNO₃ and HCl mediums were systematically studied for the employed extraction resins (TRU, DGA-N and DGA-B). Based on the results, chemical separation procedures were proposed. After cooperation with proper co-precipitation methods, the proposed procedures can be used to determine ²⁴¹Am in environmental samples. The results of evaluation showed that IEs in soil samples were completely removed and ²⁴¹Am was accurately determined for all proposed procedures.     

Solvent extraction kinetics of rare earth elements

The kinetics of solid-liquid extraction of rare earth elements (RE) (La, Ce, Sm, Dy and Yb) were studied with 1-(2-pyridylazo)-2-naphthol (PAN) at 60 degrees C using paraffin wax as a diluent. The rate of extraction is first order with respect to metal ion and hydrogen ion in the aqueous phase and second order with respect to the extractant in the organic phase. The rate-determining step is the formation of an [RE(PAN)(2)](+) complex between RE(3+) and PAN in the aqueous phase. The rate constant for the extraction was found to be about 10(11) 1 mol(-1) s(-1). The temperature dependence of extraction rate was determined and the activation parameters were calculated.     

Distribution characteristics of rare earth elements in plants from a rare earth ore area

The contents of eight rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in various plant species taken from a rare earth ore area were determined by instrumental neutron activation analysis. For a given plant, the REE patterns in root, leaf and host soil are different from each other. The REE distribution characteristics in roots of various species are very similar and resemble those in the surface water. The results of this study suggest that there is no significant fractionation between the REEs during their uptake by the plant roots from soil solution. However, the variation of the relative abundance of individual REE occurs in the process of transportation and deposition of REEs in plants.     

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.     

Mapping of rare earth elements in nuclear waste glass–ceramic using micro laser-induced breakdown spectroscopy

A micro-LIBS system was set up based on a quadruple Nd:YAG laser at 266 nm coupled with a microscope. Elemental mapping was performed on a Mo-rich glass–ceramic sample containing CaMoO₄ crystallites hundreds of microns in length and about 25 μm in section diameter. The topography of single-shot laser-induced craters was characterized using an atomic force microscope (AFM), which revealed a crater size less than 7 μm. Mappings of Mo, Ca, Sr, Al, Fe, Zr and rare earth elements such as Eu, Nd, Pr and La were undertaken. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was conducted to validate the micro-LIBS analysis. Principal components analysis calculation was used to investigate the correlation of elements in the two phases of glass–ceramic. Correlation between Ca, Sr, rare earth elements and Mo indicates their preferential incorporation into the calcium molybdate crystalline phase. Anti-correlation between Fe, Zr, Al and Mo revealed their affinity to the glass phase.