Preparation and thermal behaviour of rare earth citrate hydrates

Nine rare earth citrate hydrates (RE(C₆H₅O₇)·nH₂O,RE=La, Nd, Sm) were prepared and characterized by chemical analysis, elementary analysis, thermal analysis and IR spectra. The thermal decomposition processes were studied by using TG-DTG and IR spectra techniques. Dehydration enthalpies and dehydration entropies of 3 neodymium and 3 samarium citrate hydrates were also determined by means of DSC.     

Thermogravimetric investigation of scandium,yttrium and the rare earth metal diliturates

Thermolysis curves for scandium, yttrium, lanthanum, cerium(III), neodymium, samarium, gadolinium, dysprosium and erbium diliturates are described, Scandium diliturate forms a 15-hydrate which dehydrates in 3 steps. The other diliturates all form 12-hydrates which dehydrate smoothly. All of the anhydrous diliturates are thermally stable to about 240°.Solubilities in water for scandium, yttrium, lanthanum, cerium(lll), neodymium, samarium. gadolinium, dysprosium and erbium diliturates are given. Scandium diliturate is the most soluble and neodymium diliturate the least soluble. Solubilities of rare earth diliturates not investigated can be predicted approximately.Methods for thermogravimetric determination of yttrium, lanthanum, neodymium, samarium, gadolinium, dyprosium, and erbium as the diliturates have been developed. The precipitates are quite dense, easily handled and filterable. Weighing as the diliturate salts gives these determinations a very favorable gravimetric factor.     

Determination of rare earth elements in mineral raw materials and rare earth industry products by neutron activation analysis

To determine REE in mineral raw materials, high purity RE metals and their compounds, neutron activation analysis with extraction chromatographic REE separation has been developed. Combination of the developed RE extraction and separation procedures with subsequent -spectrometric analysis of the RE radionuclides allows to determine their content with the lower detection limit –10^–5–10^–8%. The relative standard deviation is 0.2–0.3.     

水合稀土二氯醋酸盐的合成及热分解研究

合成了La,Ce,Nd,Sm,Eu,Gd二氯醋酸盐,经化学分析,热重法和五氧化二磷真空千燥脱水法确定组成为Ln(CHCl2COO)3.nH2O(n=2,Ln=La,Ce,Nd;n=1.5,Ln=Sm;n=1.25,Ln=Eu;n=1,Ln=Gd),它们均属新水合物.用DTA-TG-DTG并用技术并辅以化学分析和红外光谱技术研究了其热分解机理,实验证明,由室温至600℃范围内,它们均发生三步主要反应:水合盐脱水变为无水盐;无水盐分解为中间产物,Ln2(OH)Cl5.3H2O[Eu盐分解为Eu2(OH)Cl5.2H2O];中间产物进一步分解为LnOCl[Ce盐为CeO2].并观察到无水盐和氯氧化物形成温度皆与原子序数呈现镧系"双一双效应".     

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...     

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.     

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.     

Mixed borohydride-chloride complexes of the rare earth elements

Mixed borohydride-chloride complexes of lanthanum and neodymium having the 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl ligand in the coordination sphere were synthesised by the reaction of potassium 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl [(DIP₂-pyr)K] with a 1:1 mixture of [Ln(BH₄)₃(THF)₃] and LnCl₃ (Ln = La, Nd). Both compounds are dimeric in the solid state. The metal atoms are bridged almost symmetrically by two μ-chlorine atoms. Quantum chemical calculations for the lanthanum compound were performed to obtain a deeper insight into the bonding in the molecule.     

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.     

Determination of rare earth elements in phosphorites by neutron activation analysis

Fourty three phosphorite rocks from Western Iraq were analyzed for eleven REE as well as uranium by NAA using IRT Reactor with a neutron flux of 2.3·10¹³ n·cm^–2·s^–1. The gamma activity from each sample was counted with a Ge(Li) and well-type HPGe, each detector connected to an on-line computer. Uranium fission products and different reaction interferences were assessed and allowed for. The results were also checked against international reference materials.     

Radiochemical neutron activation analysis of rare earth elements in peridotitic rocks

The understanding of the geochemistry of basalt petrogenesis and the nature of the upper mantle requires the examination of such rocks as peridotites which in many cases are thought to represent upper mantle material. The mineralogical composition of peridotitic rocks in such that they accommodate large proportions of such trace elements as the transition elements but very small amounts of the rare earths and hygromagmaphile elements. The last two groups are often able to provide a large amount of information leading to petrogenetic models. Owing to the extremely low concentrations of the REE in peridotitic rocks it is necessary to separate them from other elements which will interfere with their precise determination. We have used a radiochemical neutron activation analytical method which is adapted from various published methods. It involves a post-irradiation sample fusion, two separate ion-exchange chromatographic stages and finally a fluoride precipitation. The RNAA procedure is capable of providing very precise REE data for perioditic samples and we have used it for the analysis of such rocks from several geodynamic environments.